Report of the LAP/COST/WMO intercomparison of erythemal radiometers

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WORLD METEOROLOGICAL ORGANIZATION
GLOBAL ATMOSPHERE WATCH
No. 141
Report of the LAP/COST/WMO
Intercomparison of Erythemal Radiometers
(Thessaloniki, Greece, 13-23 September 1999)

WORLD METEOROLOGICAL ORGANIZATION
GLOBAL ATMOSPHERE WATCH
No. 141
Report of the LAP/COST/WMO
Intercomparison of Erythemal Radiometers
(Thessaloniki, Greece, 13-23 September 1999)
A. Bais, C. Topaloglou, S. Kazadtzis, M. Blumthaler, J. Schreder,
A. Schmalwieser, D. Henriques and M. Janouch
WMO TD No. 1051

i
TABLE OF CONTENTS
1. INTRODUCTION ................................................................................................................. 1
2. SETUP AND MEASUREMENTS ......................................................................................... 1
2.1 Location and conditions................................................................................................ 1
2.2 Instrumentation............................................................................................................. 1
2.3 Laboratory characterization ................................................................................. 4
2.3.1 Spectral response ............................................................................................. 4
2.3.2 Angular response.............................................................................................. 5
3. DATA ANALYSIS AND DISCUSSION ................................................................................ 6
3.1 Laboratory characterization .......................................................................................... 6
3.1.1 Spectral response ............................................................................................. 6
3.1.2 Angular response .............................................................................................. 8
3.2 Methodologies for deriving the calibration factors ......................................................... 8
3.2.1 Direct comparisons with measurements of erythemal irradiance....................... 8
3.2.2 Direct comparisions with detector-weighted integrals of spectral irradiance...... 8
3.3 Outdoor measurements ................................................................................................ 9
4.REFERENCES .................................................................................................................... 14
ANNEX A - Relative spectral responses of the radiometers as provided by the instrument
manufacturers together with those measured at LAP in September 1999
ANNEX B - Cosine errors of the radiometers, a function of zenith angle, as measured at LAP in
September 1999
ANNEX C - Ratio of CIE- weighted irradiance derived from the spectroradiometer to the
irradiance measured by each radiometer. All ratios are normalized to unity at
noon
ANNEX D - Ratios of SRF-weighted irradiance derived from the spectroradiometer to the
irradiance measured by each radiometer. All ratios are normalized to unity at
noon.

1
1. INTRODUCTION
The intercomparison campaign and laboratory characterization of erythemal radiometers
held in Thessaloniki, Greece, from 13 to 23 September 1999 was a venture co-organized by the
Laboratory of Atmospheric Physics (LAP) of the University of Thessaloniki, the EC COST Action
on “UV-B Forecasting” and the World Meteorological Organization (WMO). Twenty-nine
instruments from 14 countries took part in the campaign, representing all of the most widely used
instrument types. A similar campaign took place in 1995 in Finland, the results of which are
presented in Leszczynski et al., 1997 and 1998.
The objective of the campaign was to verify the absolute calibration of the instruments with
respect to spectroradiometric measurements, and to determine their spectral and angular
responses in the laboratory. The calibration factors for all radiometers were determined by direct
comparison to the integrals of global irradiance spectra weighted with the CIE action spectrum
(McKinlay and Diffey, 1987), as a function of solar elevation angle. In addition, the radiometric
calibration of the radiometers was established by comparison to the integrals of the spectral
measurements weighted with the spectral response of each radiometer.
2. SETUP AND MEASUREMENTS
2.1 Location and conditions
The intercomparison campaign and the laboratory characterization took place in
Thessaloniki, Greece, from 13 to 23 September 1999. The solar radiation measurements were
carried out on the roof of the building of the Physics Department of the Aristotle University, where
the Laboratory of Atmospheric Physics is situated (22.97°E, 40.5°N, 60 m a.s.l.). At this location
and time of the year the highest solar elevation was about 52°.
The first day of the outdoor intercomparison (16 September 1999) was very clear and only
the variability of the aerosols produced some disturbances to the, otherwise smooth, diurnal
course of the radiation field. Clouds dominated the other two days, with light rain between 12:40
and 13:20 UT on 17 September and moderate rain showers after 15:45 UT on 18 September. The
total ozone column varied during these 3 days from 317 to 329 DU and the aerosol optical
thickness at 340 nm varied between 0.6 and 0.8 during the first day.
2.2 Instrumentation
Twenty-nine instruments from 14 countries took part in the campaign, representing the
most widely used instrument types for erythemal solar radiation measurements, namely the SL-
501 of Solar Light Inc., the UVB-1 of Yankee Environmental Systems Inc., the UV-S-A/E-T of
Scintec, and the BW 100 of Vital. An instrument constructed at the University of Moscow (MO-
MSU) was also present. Finally, two instruments, the MS-210D of EKO and the CUV 3 of Kipp &
Zonen also took part in the campaign but their sensitivity was in the UV-A part of the spectrum. A
list of the participating institutes and the corresponding types of radiometers used by each of them
is shown in Table 1. Each instrument was assigned with a three-digit identification number, the
first two denoting the country and the third a sequence number for the each instrument from the
same country.
Two ultraviolet spectroradiometers were used to provide the reference for the
intercomparison, a Bentham DTM-300 of the University of Innsbruck and the local Brewer Mk III of
LAP. The first was used as the primary instrument due to its wider spectral range, which covers
the entire spectral response range of the radiometers, its ability to record one scan within 2
minutes thus minimizing the effects of changing atmospheric conditions and solar elevation, and,
finally, due to its superior performance with respect to the cosine error in the measured
irradiances. The Brewer Mk III was used as a secondary instrument for monitoring the stability of
the Bentham during the campaign.

2
Table 1: List of participants and instrument types
COUNTRY INSTITUTE TYPE OF RADIOMETER
Austria University of Innsbruck, Institute of Medical
Physics
University of Veterinary Medicine
SL 501 (2 units)
SL 501 (2 units)
Canada Atmospheric Environment Service (now the Me-
teorological Service of Canada)
YES UVB-1
SL 501
CUV 3
Czech Republic Solar and Ozone Observatory
Czech Hydrometeorological Institute
SL 501 (2 units)
Finland Finnish Meteorological Institute
STUK
SL 501
SL 501
Germany DWD
IFU
UV-S-A/E-T
SL 501
Greece Aristotle University of Thessaloniki SL 501
YES UVB-1
Italy CNR-IATA Vital BW 100
EKO MS 210D
Netherlands RIVM SL 501
Poland Institute of Meteorology and Water Management,
Centre of Aerology
SL 501 (2 units)
Portugal Instituto de Meteorologia SL 501
Russian Federa-
tion
Meteorological Observatory
Moscow State University
YES UVB-1
MO-MSU
Spain Instituto Nacional de Meteorologia YES (2 units)
Sweden SMHI
SSI
SL 501
SL 501
Switzerland Swiss Meteorological Institute SL 501
The two spectroradiometers were compared on 15 September. Both performed
synchronized (at every wavelength) measurements every 30 minutes from sunrise to sunset. Their
spectral ratio was wavelength dependent, with the Brewer overestimating by about 10% in the
UV-B and by 2-4 % in the UV-A. This dependence is attributed to the different calibration
standards used by the two instruments. The Brewer was calibrated against a NIST traceable
(through Optronic Laboratories Inc.) DWX lamp, while the Bentham was calibrated against a FEL
lamp traceable to the PTB standards. Despite the wavelength dependence the ratio of the two
instruments throughout the day was stable to within 2-3 %. Comparisons of spectra during the
other two days (without being synchronized) showed that the two instruments continued to agree
to at least within 5%.
The radiometers were mounted on a specially constructed platform, with their optical axis
directed to the zenith (see Figure 1). All instruments were arranged to have their reference plates
at the same height –to avoid shadowing each other– and the distance between them was
approximately 40 cm. The platform was about 1.5 m above the floor in order to obtain the best
possible field of view for the radiometers and to avoid any interference from the operators working
close to them. The spectroradiometers were located at the side of the platform so that their
diffusers were at the same level with the entrance optics of the radiometers. The height of the
physical obstacles above the horizon (in degrees) is shown as a function of azimuth in Figure 2.
Given that the horizon is not so bright in the UV and that the instruments were equipped with
cosine diffusers, the existing obstacles were not expected to significantly affect the
measurements. In addition, the differences in the field of view –due to the presence of the
obstacles– between the instruments were taken as too small to affect the intercomparison results.

3
Figure 2. Diagram showing the elevation angle of the obstacles around the campaign site
as a function of azimuth.
The control units of the instruments were located inside the laboratory, being about 10 m
away to the NW of the platform. The analog signals were recorded by two different computers
through two A/D converters of 12-bit resolution. The sampling of the signal was done about every
3 sec and the averages over one minute with the associated standard deviation were recorded.
The time of the computer clocks was maintained to within ±1 sec with the use of an Internet time-
server.
Figure 1. Instruments layout on the roof of the Physics Department of
AUTH during the measurement campaign (southwest view)
0
45
90
135
180
225
270
315
80 60 40 20 0

4
The measurements of the digital meters (most of the SL-501) were controlled and collected
by their own digital recorders. In a few cases two meters shared the same recorder. The time of
the recorders was checked every morning and afternoon, and, where needed, appropriate
corrections were applied. In general, none of them was ever off by more than a few seconds. On
the first day, the recording time step was set to one minute and the scaling factor to 1, and the
automatic subtraction of the dark signal (adjustment of the offset) was disabled. Unfortunately, the
selection of one-minute time steps, in conjunction with the selected scaling factor of unity,
introduced precision problems, which are discussed in detail in section 3.2. At the end of the first
day the scaling factor was changed to 10, to achieve one more digit in the recorded data, thus
increasing their precision.
The protocol of the campaign included three full days of outdoor- and 7 days of
laboratory-measurements. Although all instruments were expected to arrive on the first day of the
campaign, some of them were delayed and were delivered either on the second or on the third day
of the outdoor measurements. Consequently they missed the first –and only– clear day of the
campaign, and therefore the calculated calibration factors for these instruments are of higher
uncertainty.
2.3 Laboratory characterization
For the laboratory characterization of the radiometers (spectral and angular response
determination), the newly developed facility at LAP was used. The facility comprises a powerful
light source (1000 W Xe arc lamp) equipped with a water filter to cut off the infrared radiation, a
SPEX 1680 double monochromator, and a calibrated photodiode which is used as reference. The
quasi-monochromatic beam is divided into two parts with the help of a quartz beam splitter to
enable simultaneous sampling of the radiometer and the photodiode at each wavelength, or at
each incidence angle, depending on the type of measurement. About 95% of the power was
directed towards the radiometer and the remaining 5% to the photodiode. The radiometers were
mounted on a 360° rotation table after the exit slit of the monochromator, with their optical axis
coinciding with the output beam. A schematic of the system’s layout is shown in Figure 3. The
signal of the radiometers was recorded simultaneously with the signal of the photodiode using a
16-bit analog to digital converter. Specifically, for the SL-501 meters, the signal from their control
unit was directed to the same data acquisition system through a serial connection. The exit side of
the monochromator together with the radiometer and the photodiode were covered with thick black
cloth to eliminate stray light from the surroundings. Prior to each measurement, the effectiveness
of the optical isolation of the system was tested by sampling the photodiode with a handheld digital
voltmeter. During this measurement the light from the source was blocked at the entrance of the
monochromator to enable monitoring of the dark signal only.
2.3.1 Spectral response
The relative spectral response of the broadband radiometers was measured for most
instruments in the region 270-360 nm at 2 nm steps. The instruments were placed at different
distances from the exit slit of the monochromator to optimize the level of their signal, occasionally
using a quartz lens placed between the beam splitter and the radiometer. The measurements
were carried out using slits with effective bandwidth of 4.5 nm for the Solar Light meters, and 9 nm
for most of the other meters. The wavelength setting of the monochromator was done manually
with an uncertainty of about 0.1 nm. Given the coarse resolution of the measurements (4.5 or 9
nm) this uncertainty is not expected to introduce significant errors in the results. At each
wavelength the radiometers were sampled about 100 times and their average and standard
deviation were recorded. When the control units of the Solar Light meters were used, the sampling
rate was slower (due to the serial transmission) so the average was made from about 7
measurements only. The duration of one scan lasted for about 15-30 minutes, depending on the
last wavelength with measurable signal.

5
2.3.2 Angular response
The angular response was measured at one wavelength close to the radiometer’s
maximum sensitivity, and at one plane, 90° either side of the normal incidence of the output beam.
The measurements were carried out at steps of 5° using slits with effective bandwidth of 4.5 nm.
The positioning of the radiometers at a given angle was done manually with precision of at least
0.1°.
Positioning of the radiometer for the measurement of its angular response is one of the
most critical parameters for the success of the measurement. First, the radiometer should be
rotated around an axis passing exactly from its centre and should be contained in the same plane
with the surface of its sensitive area (e.g. its diffuser). This can be achieved with careful alignment.
Ideally the beam from the monochromator should be homogeneous and large enough to overfill
the window of the radiometer. The only way to homogenize the output beam is to use a diffuser.
However, a diffuser would decrease dramatically the signal, making the measurements too
difficult, especially for large angles of incidence. During this campaign, only for a few instruments
with higher sensitivity was it possible to use a diffuser for the homogenization of the beam. For the
rest of the instruments various combinations of distances and beam sizes were tried to achieve the
best possible result. As it is shown later, these trials were not always successful.
A critical point regarding the alignment of a radiometer for cosine response measurements
is the definition of its optical axis. In principle, this axis should be perpendicular at the centre of the
radiometer’s diffuser, assuming that it is accurately leveled. In the alignment procedure it was
assumed that the surface of the spirit level, which is used for the leveling of the radiometer, is
parallel with the surface of the diffuser, and therefore this surface was used as reference for the
alignment.
After the preliminary on-site evaluation of the results of a few of the cosine measurements,
it appeared that this procedure was not as accurate as initially anticipated, mainly due to the
alignment procedure in combination with the non-homogeneity of the measured beam. Following
these results, the remaining instruments were aligned using a slightly different procedure, but most
importantly, by using a diffuser to achieve uniform illumination. The results from this second
attempt were far better. Unfortunately this procedure could not be applied to the whole set of
instruments since some of them were shipped back to their host institutes immediately after the
Figure 3. Schematic of the facility for the characterization of broadband
radiometers operating at LAP.

6
completion of the outdoor measurements, to minimize the gaps in their regular operation at their
home sites. An example illustrating the differences in measuring the angular response of a
radiometer using the two alignment methods is shown in Figure 4. Apparently, the marked
asymmetry shown from the first method of measurement has disappeared when the second
alignment method was used.
3. DATA ANALYSIS AND DISCUSSION
3.1 Laboratory characterization
3.1.1 Spectral response
The measurements of the “quasi-monochromatic” irradiance from the monochromator,
made simultaneously with the radiometers and the Reference photodiode, were used to derive the
spectral responses, according to the following Equation:
)(
)(
)(
λ
λ
λ
R
E
E
S=(1)
where E() is the irradiance measured by the radiometer and ER() the irradiance measured by
the photodiode.
Before E() is used in Equation 1, the background signal was subtracted from all
measurements. For the analog instruments this signal was measured by a hand-held voltmeter
(see 2.3.1), while for the digital instruments (mainly SL-501) their offset as determined from the
outdoor measurements during the night was used. The appropriate removal of the background
signal is very important for the determination of the spectral response, particularly in the UV-A
where these instruments are 3-4 orders of magnitude less sensitive. Therefore, the system ought
to be able to determine this signal with precision of at least 10-4 or 10-5.
Finally the calculated spectral response S() was normalized to unity at the wavelength
where the maximum response was found.
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Angular response
First angular respons e
Second angular response
Figure 4. The angular response of a radiometer as determined by the two
different alignment methods

7
The most important problem encountered in the process of the spectral response
measurements was the significant decrease of the system’s throughput above 330 nm. This, in
combination with the very low sensitivity of the erythemal detectors in the UV-A, resulted in very
low output signals from the radiometers, hence inducing difficulties in continuing the
measurements at the higher UV-A wavelengths. In some cases the background signal of the
radiometers was slightly negative which resulted also in negative signals at some wavelengths in
the UV-A. Unfortunately this case was not taken into account in the control software of the unit,
and therefore the measurements were interrupted at the first occurrence of a negative signal. This
was an additional reason for the short range of the spectral response curves of some instruments.
A typical example of a relative response as measured in this campaign is shown in Figure
5, together with the response supplied by the manufacturer. Similar plots for all instruments that
were measured in the laboratory are shown in Annex A. In a few cases spectral responses
measured at other campaigns are also shown for comparison.
The general observation is that the spectral responses measured during this campaign
agree quite satisfactorily with those supplied by the manufacturers only at wavelengths below
about 330 nm. At higher wavelengths significant deviations occur, without being able to determine
confidently which of the two responses is closer to the truth. In the UV-A, most of the measured
responses are higher compared with those from the instrument certificates, with the exception of
3-4 instruments, whose responses stop very early due to the interruption of the measurements.
The measurement of the spectral response of the erythemal radiometers is highly
uncertain at the high-wavelengths end due to the reduced signal and the increased measurement
uncertainty. On the other hand, this is a critical region for these instruments because of its
significant contribution to the erythemal irradiance, as a result of the high intensities of solar
irradiance. Therefore more efficient techniques are needed for the accurate determination of the
spectral response at these wavelengths.
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
Solar Light S/N 0922 (Se1)
Measured (4.5nm FWHM)
Certificate
Figure 5. Spectral response of an erythemal radiometer as measured in this
campaign (circles) and as provided by its manufacturer (squares).

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3.1.2 Angular response
The angular response was calculated from the ratio of the irradiance measured at each
angle of incidence to the irradiance at normal incidence. As mentioned in 2.3.2, for several
instruments the alignment method for taking the angular response measurements was inadequate
and therefore, only for a subset of them are the angular responses considered reliable. For those
instruments cosine correction factors were calculated for their measurements during the outdoor
campaign, following the methodology described in Bais et al, (1998). The distribution of the diffuse
radiation was assumed isotropic and the ratio of direct to global irradiance was calculated from the
direct and global spectral measurements of the Bentham spectroradiometer. Only a subset of the
measured angular responses (i.e. those considered reliable) is presented in Annex B, in the form
of the cosine error from the ideal response. The calculated cosine correction factors were not used
in the comparisons with the spectroradiometric data because: a) only for a few instruments were
the cosine responses measured correctly and b) since during the regular operation of the
broadband detectors at their home sites, ancillary data needed for the calculation of cosine
correction factors were in most cases unavailable.
3.2 Methodologies for deriving the calibration factors
Two methods can be followed for the absolute calibration of an erythemal radiometer. Both
of them are based on comparisons of the measured signal of the radiometer with integrals of
spectral irradiance measurements, weighted for each case with the appropriate spectral response
function.
3.2.1 Direct comparisons with measurements of erythemal irradiance
The output signal of the radiometer, given in any instrument-specific units (e.g. Volts), is
compared with synchronous and collocated measurements of erythemal irradiance, which are
derived by integrating global irradiance spectra weighted with the response function for erythema
(CIE). The ratio of the two quantities is regarded as the calibration factor of the radiometer. The
actual spectral response of the radiometer (SRF) is generally different from the CIE function, so,
changes in the shape of the global irradiance spectrum are reflected differently in the output of the
radiometer and in the integral of the CIE weighted irradiance. On the other hand, changes in the
absolute level of the spectrum will cause only proportional changes in both quantities.
The shape of the solar irradiance spectrum at the ground is mainly determined by the
ozone column and the solar elevation angle, and to a lesser extent, by aerosols and other
parameters. Thus, the calibration factor of a radiometer, as defined above, should be also a
function of total ozone and solar elevation. If the total ozone on a given day is stable, the
calibration factor will vary smoothly with solar elevation. As solar elevation angle increases this
variation becomes less significant, and at elevation angles larger than about 50° the calibration
factor can be considered constant, and can be represented by its average over this range of solar
elevation angles.
The use of this calibration factor to measurements taken at lower solar elevations requires
the application of appropriate corrections. Corrections would be required also to compensate for
the effect of differences in the total ozone column between the day of the measurement and the
day of the calibration factor determination. These instrument-specific correction factors can be
derived from radiative transfer calculations with the use of the SRF of the radiometer.
3.2.2 Direct comparisons with detector-weighted integrals of spectral irradiance
The difference of this method with the previous one is that the output signal of the
radiometer is compared with the integral of global spectral irradiance measurements weighted with
its actual spectral response function, instead of the CIE function. The ratio of the two quantities
determines the “radiometric” calibration factor of the radiometer, and an appropriate function would
be required to convert it to erythemal irradiance. Assuming that SRF is accurately known, the

9
elation between the measurements of the radiometer and the integrals of the SRF-weighted
spectral measurements should be independent of the global irradiance spectrum, and thus from
total ozone and solar elevation.
The function to convert the measurement from SRF- to CIE-weighted irradiance depends,
for the reasons discussed in 3.2.1, on total ozone and solar elevation. For a given instrument,
these conversion functions can be pre-calculated for a range of total ozone and solar elevation
angles with the aid of a suitable radiative transfer model.
The advantage of the second method is that the procedure for the determination of the
instrument’s calibration factor is independent of the conditions during the calibration (total ozone
and solar elevation). In fact this method can be used also as an independent check of the
radiometer’s SRF. If it is wrongly measured, the calibration factor will vary with solar elevation and
total ozone, and such behavior can be detected immediately with only a few hours of data.
The advantage of the first method is that the determinations of the calibration factor can
also be done by comparing with a broadband radiometer that provides reliable measurements,
without it being necessary to have a spectroradiometer, which is expensive and difficult to maintain
and operate. Its disadvantage is that the calibration factor has higher uncertainty since small
variations of the total ozone during the period of measurements may increase the dispersion of the
ratios that form the average. Also, if measurements at high solar elevations are not available (due
to location or time of the year), the uncertainty in the determination of the calibration factor will be
higher.
The second method has the advantage that both the signal of the radiometer and the
integrals derived from the spectroradiometric measurements will vary similarly with changes in
total ozone and solar elevation, as they both represent the same radiometric quantity (SRF-
weighted irradiance). Thus their ratios throughout the day or even days are expected to be the
same. Ideally, even a single measurement could be sufficient to determine the radiometric
calibration factor. The disadvantage of the method is that the spectral response of the radiometer
must be known with very high accuracy otherwise the ratios during the day would vary with solar
elevation and total ozone. The latter suggests that this method can be also used to confirm the
validity of the spectral response function of the broadband radiometer.
Both methods require the availability of concurrent total ozone measurements, either for
the calculation of correction factors (first method), or for the selection of the appropriate
conversion function (second method). Nowadays, total ozone is readily available from satellites, so
this requirement can be easily satisfied for almost all locations worldwide.
Finally, it should be noted that if the SRF of the radiometer is unknown or wrongly
determined, the second method could not be used. However, problems will arise also for the first
method, since the calculation of correction factors is based on an accurate knowledge of the
instrument’s SRF.
3.3 Outdoor measurements
Following the methodology discussed in the previous paragraph, ratios of the signals
produced by each radiometer to the CIE-weighted spectral measurements were calculated for
each observation of the spectroradiometer (once every 20 minutes) for all three days of the
outdoor campaign. Since the duration of one scan of the spectroradiometer was two minutes, the
average of the corresponding one-minute recordings of the broadband radiometers –after
subtracting the instrument’s offset– were used to calculate the ratios. This offset was determined
as the average of the signal during the first and the last 3 hours of each day (i.e. 0:00-3:00 and
21:00-24:00). The measurements of the digital SL-501 instruments recorded during the second
and the third day were divided by 10 to account for the scaling factor of 10 used to increase the
precision of the recorded measurements.

10
As mentioned already, the reduction of the integrating interval of these instruments during
the first day from the usual 10 min to 1 min resulted in measurements of reduced precision.
Therefore, for different intervals during the day, the measurements retained the same value for as
long as the increase (or decrease) of the irradiance from one minute to the next was not enough to
change the last (third) significant digit of the data logger. An example of this effect is shown in
Figure 6, where one-minute recordings of a digital SL-501 are shown. Because the day, during
which this problem occurred, was very clear, the diurnal variation of the erythemal irradiance was
smooth, allowing the application of corrections to these measurements using data-interpolation
techniques. The interpolation was done successively between data of one digit difference,
assuming that the data logger rounds the numbers to its last significant digit. This means that at
each step (a set of same values) the actual value would be close to the centre of the
corresponding time interval. In fact, since the rate of increase (or decrease in the afternoon) of the
erythemal irradiance with time is higher at low solar elevations and becomes smaller towards
noon, the actual value should be slightly offset from the centre towards the higher solar elevations
side. By testing several time shifts from the centre of the steps it was found that the best results
were achieved when the actual value was assumed to occur at 1/3 of the time interval from the
high solar elevation end. The interpolation procedure was tested and verified by degrading the
measurements of an analog SL-501 during the same day, thus simulating the problem that
occurred with the digital instruments. The corrected diurnal course of the example of Figure 6 is
shown with a dashed line. Apparently the uncertainty, which is introduced from this method, is
smaller as one moves towards noon, and the interpolated data during approximately the first and
last two hours of the day should be used with caution. Unfortunately this first day was the only
clear day of the intercomparison, and therefore it was essential to use those measurements for the
determination of the calibration factors, since the uncertainty due to clouds in the next two days
would be probably larger or at least comparable.
The presence of clouds may introduce significant variability of the radiation field while a
spectrum is recorded increasing the uncertainty of the calculated ratios. To eliminate such
problems, the calibration factor for each instrument was determined from data of the first day only
(cloudless day), as the average of all ratios derived within a certain range of solar elevations. The
lowest solar elevation was chosen by constraining the standard deviation of the ratios to be below
1% of their average. Typically this solar elevation was between 35° and 40°.
481216
TIME [hours]
0.00
0.01
0.02
0.03
0.04
Radiometer signal [MED min
-1
]
Raw data
Data after the interpolation
-
Figure 6. Raw (solid line) and interpolated (dashed line) data from an
SL-501 during the first day of the intercomparison.

11
For the digital SL-501 instruments the calibration factors, which were determined by
comparison to integrals derived from spectral measurements, are actually dimensionless, as the
output of the data loggers is given in radiometric units (e.g. MED hr-1) and not as electrical signals.
These calibration factors are in fact “scaling factors” of the electronically adjusted gain of the
instruments, set by the manufacturer. Thus the presently determined calibration (scaling) factors
reflect the change of the instrument’s sensitivity from the first day of its operation, assuming that
the two calibrations (the present and the manufacturer’s) are traceable to each other.
For the analog instruments the output signal was given in Volts and therefore the
calibration factors that were determined are given in Volts per Weff m-2. Depending on the type of
the instrument, these factors may be very different and therefore incomparable.
To enable a direct comparison of the diurnal behaviour of the ratios from all instruments,
these ratios were normalized with the average ratio around local noon, which is actually the
calibration factor as defined above. Plots for all instruments showing the normalized ratios as a
function of solar elevation during the three days of the outdoor campaign are produced and shown
in Annex C. On each plot the calibration factor (used also for the normalization) is shown in units
of:
()
[
]
[]
IndexUV
VoltorhrMEDoutputInstrument 1−
The calibration factors were linked to the UV Index, instead of a radiometric unit, because
these instruments are mostly used in UV Index programmes. For converting the output of the
instruments into UV Index, it was assumed that 1 MED = 210 J m-2. The total ozone on the day of
the determination of the calibration factors is also shown on the plots, because it is needed when
corrections for the total ozone are applied on the measurements (see 3.2.1). Finally, to enable
direct comparisons between the diurnal variation of the ratios between different instruments, all
figures were plotted on the same scale. A sample graph from those presented in Annex C is
shown in Figure 7.
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.6
Normalized Ratio (Bentham / broadband)
.
Scaling Fa ctor: 134.68 (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1485)
Figure 7. Ratio of the signal of an erythemal radiometer to the integral of
the CIE-weighted solar irradiance, measured by the spectroradiometer,
normalized to unit at noon.

12
From the plots of Annex C, one can see the effect of solar elevation on the ratios due to
deviations of the actual response of the radiometers from CIE. This dependence is intensified from
the effect of the cosine error of the instrument, which however, is only the order of about 2-4%. In
many instruments there is a marked difference between the morning and the afternoon ratios.
There are various potential reasons to explain this difference such as the leveling of the
instruments (mainly differences between the leveling of the radiometers and the
spectroradiometer), asymmetry in the angular response of the radiometers, temperature effects of
the radiometers or the spectroradiometer, stray light from reflections from the surrounding
obstacles (see Figure 2), non-linear response of the radiometers, etc. Specifically for the SL-501
meters, the corrections applied on their data of the first day may also contribute to this behaviour.
The same procedure was repeated for the calculation of the ratios and the calibration
factors based on the spectroradiometric data weighted by the spectral response function (SRF) of
each radiometer instead of the CIE. The corresponding plots for all instruments are shown in
Annex D. Assuming that the measurements of the spectroradiometer are accurate, these ratios
must be independent of solar elevation and ozone, enabling thus an indirect assessment of the
accuracy of the used spectral response functions for each radiometer. The example of Figure 7 is
repeated for the same instrument in Figure 8, referring in this case to the SRF-based calibration
factors. It is clear that the dependence of the ratio to solar elevation is weaker, while the remaining
dependence can be attributed to the cosine error, and to the uncertainties induced by the
measurements and the by the spectral response determination.
An indication of the stability of the instruments with time can be obtained by comparing the
calibration factors derived from this campaign to those supplied by their manufacturer. Due to the
different policies of the manufacturers to supply the calibration factors of their instruments, the
results are grouped into two tables. Table 2 refers to the CIE-based calibration factors (or scaling
factors) used by Solar Light Inc. For these instruments we did not have access to the output
signals of the instruments but only to the products in units of MED hr-1. Thus from this campaign
we could only determine the scaling factors needed to match the spectroradiometer data. For
these instruments a certificate value of unity denotes that the instrument was not re-calibrated
since it was delivered from its manufacturer. For some instruments more recent calibration
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.962
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1485)
Figure 8. Ratio of the signal of an erythemal radiometer to the integral of
the SRF-weighted solar irradiance, measured by the spectroradiometer.
The ratios are normalized to unit at noon.

13
(scaling) factors, as determined in a similar campaign that took place in 1995 at STUK, Finland,
are shown instead.
In addition, the manufacturer delivers the instruments with a calibration referring to 270 DU
of ozone column and 60° solar elevation. Therefore in Table 2 an extra column was added with the
scaling factors modified to correspond to 270 DU of total ozone. The difference in solar elevation
from 60° to 53° (in the campaign) does not produce any significant change in the calibration
factors. The change in the calibration factor is determined therefore between the one delivered by
the manufacturer and the one corresponding to 270 DU of total ozone.
Table 2: CIE-based Calibration factors of the instruments that took part in the
LAP/COST/WMO intercomparison or erythemal radiometers
Calibration factorsInstrument
Type
Serial
Number Certificate LAP 1999
(327 DU)
LAP 1999
(270 DU)
Change (%)
ID
0629 1.089 0.999 1.021 -6.3 CA2
0635 0.98S0.882 0.889 -9.3 FI2
0922 1.08S0.965 0.990 -8.3 SE1
0935 1.000 0.952 0.979 -2.1 PL1
1081 1.26S1.011 1.024 -18.7 GR1
1098 1.000 0.919 0.933 -6.7 NL1
1120 1.20S1.227 1.238 3.2 PL2
1240 1.000 1.159 1.178 17.8 AT4
1451 1.000 1.018 1.024 2.4 DE2
1466 1.11S1.065 1.074 -3.3 FI1
1483 1.000 1.016 1.028 2.8 AT2
1485 1.000 0.962 0.972 -2.8 AT1
1875 1.000 0.973 0.982 -1.8 CZ1
2706 1.000 1.258 1.278 27.8 AT3
2733 1.114 1.066 1.064 -4.5 CZ2
SL 501
3749 1.000 0.828 0.840 -16.0 PT1
1493 0.214 0.220 0.225 5.1 CH1SL 501A
4388 0.230 0.209 0.212 -8.0 SE2
S Calibration from STUK 1995 (the calibration factor is the average value at solar elevations higher than 35°
with no ozone column specified)
The corresponding data for the analog instruments (mainly those by Yankee Environmental
Systems Inc.) are shown in Table 3. In this case the original calibration factors as derived from this
campaign are presented, because their manufacturers do not specify the ozone column to which
the calibration factors correspond.
Table 3: SRF-based calibration factors of the analog-output instruments
Calibration factorsInstrument
Type
Serial
number Certificate LAP 1999
(327 DU)
Change
(%)
ID
930814 0.138 0.127 -8.0 CA1
970825 0.138 0.121 -12.3 ES1
970839 0.138 0.121 -12.3 ES2
920901 0.138 0.132 -4.3 GR2
921110 0.138 0.162 17.4 GR3
YES UVB-1
920602 0.147 0.115 -21.8 RS1
Kipp & Zonen CUV3 990086 N/A 0.412 CA3
Scintec UV-S-A/E-T 010-A-00360 0.174 0.119 -31.6 DE1
Vital BW-100 94041 1.000 1.319 31.9 IT1
EKO MS-210D S91049.04 N/A 0.991 IT2
MO-MSU 12.400 10.863 -12.4 RS2

14
For several instruments the newly determined calibration factors do not differ more than a
few percent from the ones provided by their manufacturer. On the other hand, other instruments
show deviations exceeding 20%, both on the negative and positive side. One should expect that
the sensitivity of an instrument decreases with time, and therefore the calibration factors should
also decrease. An increase in the calibration factor can be produced by a shift in its spectral
response towards longer wavelengths. The large deviations of the new calibration factors from the
ones in use show that the calibration of these instruments should be checked more frequently.
As mentioned already, for some instruments it was impossible to derive a full spectral
response for the entire spectral range 280-400 nm. An estimation of the error introduced in the
calculation of the calibration factors due to the interrupted relative responses at wavelengths below
400 nm was made by calculating the factors for the these responses, assuming a constant value
of the spectral response equal to the last measured one, for all wavelengths up to 400nm. From
this comparison it appears that the calibration factors, which are based on spectral responses of
reduced range, are generally underestimated by 0.5 to 7%, but for 2-3 instruments the
underestimation can reach 8.6%.
Calculations with both the certificate and the LAP measured spectral responses show
differences between the calibration factors, not only in their absolute values but also in the
variation they present during the course of the day. In general, the smaller the variation is during
the day, the better the spectral response used can be considered.
Acknowledgements: This campaign was supported by the World Meteorological Organization, by
the European Commission, through COST on Meteorology, Action 713 “UV-B Forecasting”, and by
the Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki. Thanks to all Institutes
listed in Table 1 for their participation by providing their instruments. Finally we would like to thank
Dr Kirsti Leszczynski and Dr Lasse Ylianttila, for their valuable comments and suggestions.
4. REFERENCES
Leszczynski K, Jokela K, Ylianttila L, Visuri R, Blumthaler M., Report of the WMO/STUK
Intercomparison of erythemally-weighted solar UV radiometers (Spring/Summer 1995, Helsinki,
Finland), World Meteorological Organization, Global Atmosphere Watch, Report No. 112, 90
pages, 1997.
Leszczynski K, Jokela K, Ylianttila L,Visuri R, Blumthaler M, Erythemally weighted radiometers in
solar UV monitoring: results from the WMO/STUK Intercomparison, Photochem. Photobiol. 67(2),
212-221, 1998.
McKinley A. F. and B. L. Diffey, A reference action spectrum for ultraviolet induced erythema in
human skin, CIE Journal 6, 17-22, 1987.
Bais, A.F., S. Kazadzis, D. Balis, C.S. Zerefos and M. Blumthaler, "Correcting global solar UV
spectra recorded by a Brewer spectroradiometer for its angular response error", Applied Optics,
37, 27, 6339-6344, 1998.

15
ANNEX A
Relative spectral responses of the radiometers as provided by the instrument manufacturers
together with those measured at LAP in September 1999

17
260 280 300 320 340 360
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (1485)
260 280 300 320 340 360 380
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certicicate
SL 501 (1483)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate (Solar Light)
UI-IMP (Jan.2000)
SL 501 (2706)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate (Solar Light)
UI-IMP (Jan.2000)
STUK (Jul.1995)
SL 501 (1240)

18
260 280 300 320 340 360
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (1875)
260 280 300 320 340 360
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (2733)
240 280 320 360 400
Wavelength (nm)
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 1493
260 280 300 320 340 360 380
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
SL 501 0629

19
240 280 320 360 400
Wavelength (nm)
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate (Solar Light)
STUK (1999)
WMO-STUK (Jul.1995)
SL 501 1466
240 280 320 360 400
Wavelength (nm)
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 19 99)
Certificate (Solar Light)
STUK (1999)
WMO-STUK (J ul 1995)
SL 501 (0635)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (0922)
260 280 300 320 340 360
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (4388)

20
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-10
1E-9
1E-8
1E-7
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (0935)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (1120)
260 280 300 320 340 360 380
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (3749)
240 280 320 360 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
SL 501 (1098)

21
260 280 300 320 340 360 380
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
SL 501 (1451)
240 280 320 360 400
Wavelength (nm)
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
SL 501 (1081)
LAP (Sep. 1999)
Certificate
LAP (Jan. 2000)
UI IMP (Jan. 2000)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
YES (920602)
260 280 300 320 340 360
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
YES (930814)

22
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 199 9)
Certificate
YES (970825)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
YES (970839)
260 280 300 320 340 360
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
YES (921110)
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-6
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
YES (920901)
LAP (Sep. 1999 )
Certificate
LAP (Jan. 1999)
UI IMP (Jan.2000)

23
240 260 280 300 320 340 360 380
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Vital BW 100
240 260 280 300 320 340 360 380 400
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
EKO MS 210D
260 280 300 320 340 360 380 400
Wavelength (nm)
1E-5
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
UV-S-A/E-T (Scintec)

24
280 300 320 340 360 380 400 420 440
Wavelength (nm)
1E-4
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
Certificate
MO-MSU
280 300 320 340 360 380 400
Wavelength (nm)
1E-3
1E-2
1E-1
1E+0
1E+1
Relative response
LAP (Sep. 1999)
CUV 3 (Kipp and Zonnen)

25
ANNEX B
Cosine error of the radiometers, as function of zenith angle, as measured at LAP in
September 1999

26

27
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 1485 (At1)
-90 -60 -30 0 30 60 90
Zenith angle (degrres)
-20
0
20
40
60
80
100
Cosine error (%)
Solar Light S/N 1483 (At2)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 2706 (At3)
-90 -60 -30 0 30 60 90
Zenith angle
-80
-60
-40
-20
0
20
Cosine error %
Solar Light S/N 1240 (At4)

28
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 06 29 (Ca2)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 1493 (Ch1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 1875 (Cz1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 2733 (Cz2)

29
-90 -60 -30 0 30 60 90
Zenith angle (degrres)
-60
-40
-20
0
20
Cosine error (%)
Scintec (De1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-40
-20
0
20
40
Cosine error (%)
EKO MS 210 D (It 2)

30
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
40
Cosine error (%)
YES S/N 920602 (Rs1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
Cosine error (%)
YES S/N 930814 (Ca1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 1081 (Gr1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-20
0
20
40
60
80
100
120
Cosine error (%)
Solar Light S/N 1451 (De2)

31
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
40
Cosine error (%)
Solar Light S/N 0922 (Se1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 4388
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 1466 (Fi1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-20
0
20
40
60
80
Cosine error (%)
Solar Light S/N 0635 (Fi2)

32
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
YES S/N 970825 (Es1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
YES S/N 970839 (Es2 )
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
Cosine error (%)
YES S/N 920901 (Gr2)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
Cosine error (%)
YES S/N 921110 (Gr3)

33
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-80
-60
-40
-20
0
20
40
Cosine error (%)
Solar Light S /N 1098 (Nl1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
40
Cosine error (%)
Solar Light S/N 0935 (Pl 1)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 1120 (Pl2)
-90 -60 -30 0 30 60 90
Zenith angle (degrees)
-100
-80
-60
-40
-20
0
20
Cosine error (%)
Solar Light S/N 3749 (Pt1)

34

35
ANNEX C
Ratios of CIE-weighted irradiance derived from the spectroradiometer to the irradiance
measured by each radiometer. All ratios are normalized to unity at noon.

36

37
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 162.26 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1240)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 176.12 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (2706)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 142.24 M ED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1483)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 134.68 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1485)

38
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 128.66 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1098)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 133.28 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (0935)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 171.78 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1120)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 115.92 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (3749)

39
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 8.36 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 analog (4388)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 135.1 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (0922)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 123.48 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (0635)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 149.1 MED
-1
.min (327 DU)
Weighting function: C IE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1466)

40
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 141.54 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1081)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 142.52 MED
-1
.min (318 DU)
Weighting function: CIE
18/09/1999
SL-501 (1451)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 5.08 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
YES 920602
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 5.08 Volt
-1
(318 DU)
Weighting function: CIE
17/09/1999
18/09/1999
YES (930814)

41
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 9.72 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
YES (970825)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 9.68 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
YES (970839)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 5.28 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
YES (920901)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 6.48 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
YES (921110)

42
10 20 30 40 50
Solar Elevation (deg)
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 39.64Volt
-1
(329 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
EKO MS 210D
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 4.76 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
UV-S-A/E-T (Scintec)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 52.76 Volt
-1
(329 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
Vital BW 100

43
0 102030405060
Elevation (degrees)
0.01
0.02
0.03
0.04
0.05
Calibration factor
MO-MSU (Rs2)
Weighting function : CIE
16/09/1999
17/09/1999
18/09/1999
0 102030405060
Elevation (degrees)
0.00
0.20
0.40
0.60
0.80
1.00
Calibration factor
Kipp and Zonnen (Ca3)
Weighting function : CIE
17/09/1999
18/09/1999

44
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 8.8 Volt
-1
(327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 analog (1493)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 139.86 MED
-1
.min (318 DU)
Weighting function: CIE
17/09/1999
18/09/1999
SL-501 (0629)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 136.22 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (1875)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Scaling Factor: 149.24 MED
-1
.min (327 DU)
Weighting function: CIE
16/09/1999
17/09/1999
18/09/1999
SL-501 (2733)

45
ANNEX D
Ratios of SRF-weighted irradiance derived from the spectroradiometer to the irradiance measured
by each radiometer. All ratios are normalized to unity at noon.

46

47
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.962
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1485)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.02
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1483)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.557
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (2706)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.357
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1240)

48
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 0.554 (W.m
2
/Volt)
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1493 analog)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.284
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1875)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.97
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (2733)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.852
Weighting function: SRF
17/09/1999
18/09/1999
SL-501 (0629)

49
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.047
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1098)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.11
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (0935)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF :1. 788
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (3749)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.846
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1120)

50
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 0.431(W.m
-2
/Volt)
Weighting func tion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (4388 analog)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF :2.146
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (0922)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.148
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1466)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.88
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (0635)

51
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.534 (W.m
-2
/Volt)
Weighting fu nction: SRF
16/09/1999
17/09/1999
18/09/1999
YES (970825)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.697 (W.m
-2
/Volt)
Weighting func tion: SRF
16/09/1999
17/09/1999
18/09/1999
YES (970839)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 0.916 (W.m
-2
/Volt)
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
YES (920901)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.182 (W.m
-2
/Volt)
Weighting func tion: SRF
16/09/1999
17/09/1999
18/09/1999
YES (921110)

52
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.258
Weighting funct ion: SRF
16/09/1999
17/09/1999
18/09/1999
SL-501 (1081)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 1.806
Weighting function: SRF
18/09/1999
SL-501 (1451)
10 20 30 40 50
Solar Elevation (deg)
1.0
1.1
1.2
1.3
1.4
1.5
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 0.575 (W.m
-2
/Volt)
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
YES (920602)
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 0.47 (W.m
-2
/Volt)
Weighting func tion: SRF
17/09/1999
18/09/1999
YES (930814)

53
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 5.018 (W.m
-2
/Volt)
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
EKO MS 210D
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 2.035 (W.m
-2
/Volt)
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
Vital BW 100
10 20 30 40 50
Solar Elevation (deg)
0.9
1.0
1.1
1.2
1.3
1.4
Normalized Ratio (Bentham / broadband)
.
Radiometric CF : 0.484 (W.m
-2
/Volt)
Weighting function: SRF
16/09/1999
17/09/1999
18/09/1999
UV-S-A/E-T (Scintec)

54
0 102030405060
Elevation (degress)
6.00
7.00
8.00
9.00
Calibration factor
MO-MSU (Rs2)
Weighting function : SRF
16/09/1999
17/09/1999
18/09/1999
0 102030405060
Elevation (degrees)
60.00
70.00
80.00
90.00
100.00
Calibration factor
Kipp and Zonnen (Ca3)
Weighting function : SRF
17/09/1999
18/09/1999

GLOBAL ATMOSPHERE WATCH
REPORT SERIES
1. Final Report of the Expert Meeting on the Operation of Integrated Monitoring Programmes,
Geneva, 2-5 September 1980
2. Report of the Third Session of the GESAMP Working Group on the Interchange of Pollutants
Between the Atmosphere and the Oceans (INTERPOLL-III), Miami, USA, 27-31 October 1980
3. Report of the Expert Meeting on the Assessment of the Meteorological Aspects of the First
Phase of EMEP, Shinfield Park, U.K., 30 March - 2 April 1981
4. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as
at April 1981
5. Report of the WMO/UNEP/ICSU Meeting on Instruments, Standardization and Measurements
Techniques for Atmospheric CO2, Geneva, 8-11; September 1981
6. Report of the Meeting of Experts on BAPMoN Station Operation, Geneva,
23-26 November, 1981
7. Fourth Analysis on Reference Precipitation Samples by the Participating World Meteorological
Organization Laboratories by Robert L. Lampe and John C. Puzak, December 1981*
8. Review of the Chemical Composition of Precipitation as Measured by the WMO BAPMoN by
Prof. Dr. Hans-Walter Georgii, February 1982
9. An Assessment of BAPMoN Data Currently Available on the Concentration of CO2 in the
Atmosphere by M.R. Manning, February 1982
10. Report of the Meeting of Experts on Meteorological Aspects of Long-range Transport of
Pollutants, Toronto, Canada, 30 November - 4 December 1981
11. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as
at May 1982
12. Report on the Mount Kenya Baseline Station Feasibility Study edited by Dr. Russell C. Schnell
13. Report of the Executive Committee Panel of Experts on Environmental Pollution, Fourth
Session, Geneva, 27 September - 1 October 1982
14. Effects of Sulphur Compounds and Other Pollutants on Visibility by Dr. R.F. Pueschel,
April 1983
15. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites
for the Year 1981, May 1983
16. Report of the Expert Meeting on Quality Assurance in BAPMoN, Research Triangle Park, North
Carolina, USA, 17-21 January 1983
17. General Consideration and Examples of Data Evaluation and Quality Assurance Procedures
Applicable to BAPMoN Precipitation Chemistry Observations by Dr. Charles Hakkarinen,
July 1983

18. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as
at May 1983
19. Forecasting of Air Pollution with Emphasis on Research in the USSR by M.E. Berlyand, August
1983
20. Extended Abstracts of Papers to be Presented at the WMO Technical Conference on
Observation and Measurement of Atmospheric Contaminants (TECOMAC), Vienna,
17-21 October 1983
21. Fifth Analysis on Reference Precipitation Samples by the Participating World Meteorological
Organization Laboratories by Robert L. Lampe and William J. Mitchell, November 1983
22. Report of the Fifth Session of the WMO Executive Council Panel of Experts on Environmental
Pollution, Garmisch-Partenkirchen, Federal Republic of Germany, 30 April - 4 May 1984 (TD
No. 10)
23. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites
for the Year 1982. November 1984 (TD No. 12)
24. Final Report of the Expert Meeting on the Assessment of the Meteorological Aspects of the
Second Phase of EMEP, Friedrichshafen, Federal Republic of Germany, 7-10 December 1983.
October 1984 (TD No. 11)
25. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as
at May 1984. November 1984 (TD No. 13)
26. Sulphur and Nitrogen in Precipitation: An Attempt to Use BAPMoN and Other Data to Show
Regional and Global Distribution by Dr. C.C. Wallén. April 1986 (TD No. 103)
27. Report on a Study of the Transport of Sahelian Particulate Matter Using Sunphotometer
Observations by Dr. Guillaume A. d'Almeida. July 1985 (TD No. 45)
28. Report of the Meeting of Experts on the Eastern Atlantic and Mediterranean Transport
Experiment ("EAMTEX"), Madrid and Salamanca, Spain, 6-8 November 1984
29. Recommendations on Sunphotometer Measurements in BAPMoN Based on the Experience
of a Dust Transport Study in Africa by Dr. Guillaume A. d'Almeida. September 1985 (TD No.
67)
30. Report of the Ad-hoc Consultation on Quality Assurance Procedures for Inclusion in the
BAPMoN Manual, Geneva, 29-31 May 1985
31. Implications of Visibility Reduction by Man-Made Aerosols (Annex to No. 14) by R.M. Hoff and
L.A. Barrie. October 1985 (TD No. 59)
32. Manual for BAPMoN Station Operators by E. Meszaros and D.M. Whelpdale. October 1985 (TD
No. 66)
33. Man and the Composition of the Atmosphere: BAPMoN - An international programme of
national needs, responsibility and benefits by R.F. Pueschel. 1986
34. Practical Guide for Estimating Atmospheric Pollution Potential by Dr. L.E. Niemeyer.
August 1986 (TD No. 134)
35. Provisional Daily Atmospheric CO2 Concentrations as Measured at BAPMoN Sites for the Year
1983. December 1985 (TD No. 77)

36. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1984. Volume I: Atmospheric Aerosol Optical Depth. October 1985 (TD No. 96)
37. Air-Sea Interchange of Pollutants by R.A. Duce. September 1986 (TD No. 126)
38. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as
at 31 December 1985. September 1986 (TD No. 136)
39. Report of the Third WMO Expert Meeting on Atmospheric Carbon Dioxide Measurement
Techniques, Lake Arrowhead, California, USA, 4-8 November 1985. October 1986
40. Report of the Fourth Session of the CAS Working Group on Atmospheric Chemistry and Air
Pollution, Helsinki, Finland, 18-22 November 1985. January 1987
41. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1982, Volume II: Precipitation chemistry, continuous atmospheric carbon dioxide and
suspended particulate matter. June 1986 (TD No. 116)
42. Scripps reference gas calibration system for carbon dioxide-in-air standards: revision of 1985
by C.D. Keeling, P.R. Guenther and D.J. Moss. September 1986 (TD No. 125)
43. Recent progress in sunphotometry (determination of the aerosol optical depth).
November 1986
44. Report of the Sixth Session of the WMO Executive Council Panel of Experts on Environmental
Pollution, Geneva, 5-9 May 1986. March 1987
45. Proceedings of the International Symposium on Integrated Global Monitoring of the State of the
Biosphere (Volumes I-IV), Tashkent, USSR, 14-19 October 1985. December 1986 (TD No.
151)
46. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites
for the Year 1984. December 1986 (TD No. 158)
47. Procedures and Methods for Integrated Global Background Monitoring of Environmental
Pollution by F.Ya. Rovinsky, USSR and G.B. Wiersma, USA. August 1987 (TD No. 178)
48. Meeting on the Assessment of the Meteorological Aspects of the Third Phase of EMEP IIASA,
Laxenburg, Austria, 30 March - 2 April 1987. February 1988
49. Proceedings of the WMO Conference on Air Pollution Modelling and its Application (Volumes I-
III), Leningrad, USSR, 19-24 May 1986. November 1987 (TD No. 187)
50. Provisional Daily Atmospheric Carbon Dioxide Concentrations as Measured at BAPMoN Sites
for the Year 1985. December 1987 (TD No. 198)
51. Report of the NBS/WMO Expert Meeting on Atmospheric CO2 Measurement Techniques,
Gaithersburg, USA, 15-17 June 1987. December 1987
52. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1985. Volume I: Atmospheric Aerosol Optical Depth. September 1987
53. WMO Meeting of Experts on Strategy for the Monitoring of Suspended Particulate Matter in
BAPMoN - Reports and papers presented at the meeting, Xiamen, China, 13-17 October 1986.
October 1988

54. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1983, Volume II: Precipitation chemistry, continuous atmospheric carbon dioxide and
suspended particulate matter (TD No. 283)
55. Summary Report on the Status of the WMO Background Air Pollution Monitoring Network as
at 31 December 1987 (TD No. 284)
56. Report of the First Session of the Executive Council Panel of Experts/CAS Working Group on
Environmental Pollution and Atmospheric Chemistry, Hilo, Hawaii, 27-31 March 1988. June
1988
57. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1986, Volume I: Atmospheric Aerosol Optical Depth. July 1988
58. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at BAPMoN sites
for the years 1986 and 1987 (TD No. 306)
59. Extended Abstracts of Papers Presented at the Third International Conference on Analysis and
Evaluation of Atmospheric CO2 Data - Present and Past, Hinterzarten, Federal Republic of
Germany, 16-20 October 1989 (TD No. 340)
60. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1984 and 1985, Volume II: Precipitation chemistry, continuous atmospheric carbon
dioxide and suspended particulate matter.
61. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data for 1987 and 1988, Volume I: Atmospheric Aerosol Optical Depth.
62. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at BAPMoN sites
for the year 1988 (TD No. 355)
63. Report of the Informal Session of the Executive Council Panel of Experts/CAS Working Group
on Environmental Pollution and Atmospheric Chemistry, Sofia, Bulgaria, 26 and 28 October
1989
64. Report of the consultation to consider desirable locations and observational practices for
BAPMoN stations of global importance, Bermuda Research Station, 27-30 November 1989
65. Report of the Meeting on the Assessment of the Meteorological Aspects of the Fourth Phase
of EMEP, Sofia, Bulgaria, 27 and 31 October 1989
66. Summary Report on the Status of the WMO Global Atmosphere Watch Stations as at
31 December 1990 (TD No. 419)
67. Report of the Meeting of Experts on Modelling of Continental, Hemispheric and Global Range
Transport, Transformation and Exchange Processes, Geneva, 5-7 November 1990
68. Global Atmospheric Background Monitoring for Selected Environmental Parameters. BAPMoN
Data For 1989, Volume I: Atmospheric Aerosol Optical Depth
69. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at Global
Atmosphere Watch (GAW)-BAPMoN sites for the year 1989 (TD No. 400)
70. Report of the Second Session of EC Panel of Experts/CAS Working Group on Environmental
Pollution and Atmospheric Chemistry, Santiago, Chile, 9-15 January 1991 (TD No. 633)

71. Report of the Consultation of Experts to Consider Desirable Observational Practices and
Distribution of GAW Regional Stations, Halkidiki, Greece, 9-13 April 1991 (TD No. 433)
72. Integrated Background Monitoring of Environmental Pollution in Mid-Latitude Eurasia by Yu.A.
Izrael and F.Ya. Rovinsky, USSR (TD No. 434)
73. Report of the Experts Meeting on Global Aerosol Data System (GADS), Hampton, Virginia, 11
to 12 September 1990 (TD No. 438)
74. Report of the Experts Meeting on Aerosol Physics and Chemistry, Hampton, Virginia, 30 to
31 May 1991 (TD No. 439)
75. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at Global
Atmosphere Watch (GAW)-BAPMoN sites for the year 1990 (TD No. 447)
76. The International Global Aerosol Programme (IGAP) Plan: Overview (TD No. 445)
77. Report of the WMO Meeting of Experts on Carbon Dioxide Concentration and Isotopic
Measurement Techniques, Lake Arrowhead, California, 14-19 October 1990
78. Global Atmospheric Background Monitoring for Selected Environmental Parameters BAPMoN
Data for 1990, Volume I: Atmospheric Aerosol Optical Depth (TD No. 446)
79. Report of the Meeting of Experts to Consider the Aerosol Component of GAW, Boulder, 16 to
19 December 1991 (TD No. 485)
80. Report of the WMO Meeting of Experts on the Quality Assurance Plan for the GAW, Garmisch-
Partenkirchen, Germany, 26-30 March 1992 (TD No. 513)
81. Report of the Second Meeting of Experts to Assess the Response to and Atmospheric Effects
of the Kuwait Oil Fires, Geneva, Switzerland, 25-29 May 1992 (TD No. 512)
82. Global Atmospheric Background Monitoring for Selected Environmental Parameters BAPMoN
Data for 1991, Volume I: Atmospheric Aerosol Optical Depth (TD No. 518)
83. Report on the Global Precipitation Chemistry Programme of BAPMoN (TD No. 526)
84. Provisional Daily Atmospheric Carbon Dioxide Concentrations as measured at GAW-BAPMoN
sites for the year 1991 (TD No. 543)
85. Chemical Analysis of Precipitation for GAW: Laboratory Analytical Methods and Sample
Collection Standards by Dr Jaroslav Santroch (TD No. 550)
86. The Global Atmosphere Watch Guide, 1993 (TD No. 553)
87. Report of the Third Session of EC Panel/CAS Working Group on Environmental Pollution and
Atmospheric Chemistry, Geneva, 8-11 March 1993 (TD No. 555)
88. Report of the Seventh WMO Meeting of Experts on Carbon Dioxide Concentration and Isotopic
Measurement Techniques, Rome, Italy, 7 - 10 September 1993, (edited by Graeme I. Pearman
and James T. Peterson) (TD No. 669)
89. 4th International Conference on CO2 (Carqueiranne, France, 13-17 September 1993) (TD No.
61)
90. Global Atmospheric Background Monitoring for Selected Environmental Parameters GAW Data
for 1992, Volume I: Atmospheric Aerosol Optical Depth (TD No. 562)

91. Extended Abstracts of Papers Presented at the WMO Region VI Conference on the
Measurement and Modelling of Atmospheric Composition Changes Including Pollution
Transport, Sofia, 4 to 8 October 1993 (TD No. 563)
92. Report of the Second WMO Meeting of Experts on the Quality Assurance/Science Activity
Centres of the Global Atmosphere Watch, Garmisch-Partenkirchen, 7-11 December 1992 (TD
No. 580)
93. Report of the Third WMO Meeting of Experts on the Quality Assurance/Science Activity Centres
of the Global Atmosphere Watch, Garmisch-Partenkirchen, 5-9 July 1993 (TD No. 581)
94. Report on the Measurements of Atmospheric Turbidity in BAPMoN (TD No. 603)
95. Report of the WMO Meeting of Experts on UV-B Measurements, Data Quality and
Standardization of UV Indices, Les Diablerets, Switzerland, 25-28 July 1994 (TD No. 625)
96. Global Atmospheric Background Monitoring for Selected Environmental Parameters WMO
GAW Data for 1993, Volume I: Atmospheric Aerosol Optical Depth
97. Quality Assurance Project Plan (QAPjP) for Continuous Ground Based Ozone Measurements
(TD No. 634)
98. Report of the WMO Meeting of Experts on Global Carbon Monoxide Measurements, Boulder,
USA, 7-11 February 1994 (TD No. 645)
99. Status of the WMO Global Atmosphere Watch Programme as at 31 December 1993
(TD No. 636)
100. Report of the Workshop on UV-B for the Americas, Buenos Aires, Argentina,
22-26 August 1994
101. Report of the WMO Workshop on the Measurement of Atmospheric Optical Depth and
Turbidity, Silver Spring, USA, 6-10 December 1993, (edited by Bruce Hicks) (TD No. 659)
102. Report of the Workshop on Precipitation Chemistry Laboratory Techniques, Hradec Kralove,
Czech Republic, 17-21 October 1994 (TD No. 658)
103. Report of the Meeting of Experts on the WMO World Data Centres, Toronto, Canada,
17-18 February 1995, (prepared by Edward Hare) (TD No. 679)
104. Report of the Fourth WMO Meeting of Experts on the Quality Assurance/Science Activity
Centres (QA/SACs) of the Global Atmosphere Watch, jointly held with the First Meeting of the
Coordinating Committees of IGAC-GLONET and IGAC-ACE, Garmisch-Partenkirchen,
Germany, 13 to 17 March 1995 (TD No. 689)
105. Report of the Fourth Session of the EC Panel of Experts/CAS Working Group on Environmental
Pollution and Atmospheric Chemistry (Garmisch, Germany, 6-11 March 1995) (TD No. 718)
106. Report of the Global Acid Deposition Assessment (edited by D.M. Whelpdale and M-S. Kaiser)
(TD No. 777)
107. Extended Abstracts of Papers Presented at the WMO-IGAC Conference on the Measurement
and Assessment of Atmospheric Composition Change (Beijing, China, 9-14 October 1995) (TD
No. 710)
108. Report of the Tenth WMO International Comparison of Dobson Spectrophotometers (Arosa,
Switzerland, 24 July - 4 August 1995)

109. Report of an Expert Consultation on 85Kr and 222Rn: Measurements, Effects and Applications
(Freiburg, Germany, 28-31 March 1995) (TD No. 733)
110. Report of the WMO-NOAA Expert Meeting on GAW Data Acquisition and Archiving (Asheville,
NC, USA, 4-8 November 1995) (TD No. 755)
111. Report of the WMO-BMBF Workshop on VOC Establishment of a “World Calibration/Instrument
Intercomparison Facility for VOC” to Serve the WMO Global Atmosphere Watch (GAW)
Programme (Garmisch-Partenkirchen, Germany, 17-21 December 1995) (TD No. 756)
112. Report of the WMO/STUK Intercomparison of Erythemally-Weighted Solar UV Radiometers,
Spring/Summer 1995, Helsinki, Finland (TD No. 781)
113. The Strategic Plan of the Global Atmosphere Watch (GAW) (TD No. 802)
114. Report of the Fifth WMO Meeting of Experts on the Quality Assurance/Science Activity Centres
(QA/SACs) of the Global Atmosphere Watch, jointly held with the Second Meeting of the
Coordinating Committees of IGAC-GLONET and IGAC-ACEEd, Garmisch-Partenkirchen,
Germany, 15-19 July 1996 (TD No. 787)
115. Report of the Meeting of Experts on Atmospheric Urban Pollution and the Role of NMSs
(Geneva, 7-11 October 1996) (TD No. 801)
116. Expert Meeting on Chemistry of Aerosols, Clouds and Atmospheric Precipitation in the Former
USSR (Sankt Peterburg, Russian Federation, 13-15 November 1995)
117. Report and Proceedings of the Workshop on the Assessment of EMEP Activities Concerning
Heavy Metals and Persistent Organic Pollutants and their Further Development (Moscow,
Russian Federation, 24-26 September 1996) (Volumes I and II) (TD No. 806)
118. Report of the International Workshops on Ozone Observation in Asia and the Pacific Region
(IWOAP, IWOAP-II), (IWOAP, 27 February-26 March 1996 and IWOAP-II, 20 August-
18 September 1996) (TD No. 827)
119. Report on BoM/NOAA/WMO International Comparison of the Dobson Spectrophotometers
(Perth Airport, Perth, Australia, 3-14 February 1997), (prepared by Robert Evans and
James Easson) (TD No. 828)
120. WMO-UMAP Workshop on Broad-Band UV Radiometers (Garmisch-Partenkirchen, Germany,
22 to 23 April 1996) (TD No. 894)
121. Report of the Eighth WMO Meeting of Experts on Carbon Dioxide Concentration and Isotopic
Measurement Techniques (prepared by Thomas Conway) (Boulder, CO, 6-11 July 1995) (TD
No. 821)
122 Report of Passive Samplers for Atmospheric Chemistry Measurements and their Role in GAW
(prepared by Greg Carmichael) (TD No. 829)
123 Report of WMO Meeting of Experts on GAW Regional Network in RA VI, Budapest, Hungary,
5 to 9 May 1997
124 Fifth Session of the EC Panel of Experts/CAS Working Group on Environmental Pollution and
Atmospheric Chemistry, (Geneva, Switzerland, 7-10 April 1997) (TD No. 898)
125. Instruments to Measure Solar Ultraviolet Radiation, Part 1: Spectral Instruments (lead author
G. Seckmeyer) (TD No. 1066)

126. Guidelines for Site Quality Control of UV Monitoring (lead author A.R. Webb) (TD No. 884)
127. Report of the WMO-WHO Meeting of Experts on Standardization of UV Indices and their
Dissemination to the Public (Les Diablerets, Switzerland, 21-25 July 1997) (TD No. 921)
128. The Fourth Biennial WMO Consultation on Brewer Ozone and UV Spectrophotometer
Operation, Calibration and Data Reporting, (Rome, Italy, 22-25 September 1996) (TD No. 918)
129. Guidelines for Atmospheric Trace Gas Data Management (Ken Masarie and Pieter Tans), 1998
(TD No. 907)
130. Jülich Ozone Sonde Intercomparison Experiment (JOSIE, 5 February to 8 March 1996), (H.G.J.
Smit and D. Kley) (TD No. 926)
131. WMO Workshop on Regional Transboundary Smoke and Haze in Southeast Asia (Singapore,
2 to 5 June 1998) (Gregory R. Carmichael). Two volumes
132. Report of the Ninth WMO Meeting of Experts on Carbon Dioxide Concentration and Related
Tracer Measurement Techniques (Edited by Roger Francey), (Aspendale, Vic., Australia)
133. Workshop on Advanced Statistical Methods and their Application to Air Quality Data Sets
(Helsinki, 14-18 September 1998) (TD No.956)
134. Guide on Sampling and Analysis Techniques for Chemical Constituents and Physical Properties
in Air and Precipitation as Applied at Stations of the Global Atmosphere Watch.
Carbon Dioxide
135. Sixth Session of the EC Panel of Experts/CAS Working Group on Environmental Pollution and
Atmospheric Chemistry (Zurich, Switzerland, 8-11 March 1999) (WMO TD No.1002)
136. WMO/EMEP/UNEP Workshop on Modelling of Atmospheric Transport and Deposition of
Persistent Organic Pollutants and Heavy Metals (Geneva, Switzerland, 16-19 November 1999)
(Volumes I and II) (TD No. 1008)
137. Report and Proceedings of the WMO RA II/RA V GAW Workshop on Urban Environment
(Beijing, China, 1-4 November 1999) (WMO-TD. 1014) (Prepared by Greg Carmichael)
138. Reports on WMO International Comparisons of Dobson Spectrophotometers, Parts I – Arosa,
Switzerland, 19-31 July 1999, Part II – Buenos Aires, Argentina (29 Nov. – 12 Dec. 1999 and
Part III – Pretoria, South Africa (18 March – 10 April 2000).
139. The Fifth Biennial WMO Consultation on Brewer Ozone and UV Spectrophotometer Operation,
Calibration and Data Reporting (Halkidiki, Greece, September 1998)(WMO TD No. 1019).
140. WMO/CEOS Report on a Strategy for Integrating Satellite and Ground-based Observations of
Ozone (WMO TD No. 1046).
141. Report of the LAP/COST/WMO Intercomparison of Erythemal Radiometers (Thessaloniki,
Greece, 13-23 September 1999) (WMO TD No. 1051).