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The Global Weather Experiment 1. The Observational Phase Through the First Special Observing Period

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The Global Weather Experiment 1. The Observational Phase Through the First Special Observing Period

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An unprecedented analysis of the atmosphere of planet Earth is currently underway with the involvement of over 140 countries in the Global Weather Experiment-the largest international scientific experiment yet attempted. After many years of planning, the Operational Year began in December of 1978. Following the field phase and data management phase, a multi-year evaluation and research program will commence and continue until the late 1980s. During this period, scientists and technicians will examine the atmosphere, the sea surface, and the upper layer of the world's oceans in the most intense survey and study ever made. A number of successes and failures occurred in preparing for the observing phase and these are mentioned as each observing system actually deployed in the field is reviewed. The focus of the paper is on the quantity of data gathered and how it was obtained. The article concludes with some suggestions for assurances of final success of the Experiment.
Content may be subject to copyright.
An occasional series reporting on U.S. and international GARP scientific, technical, and planning
activities, developments, and programs, presented as a public service to the meteorological com-
munity by the American Meteorological Society through arrangements with the U.S. Committee
on the Global Atmospheric Research Program of the National Academy of Sciences-National
Research Council. Opinions expressed in "GARP Topics" do not necessarily reflect the point of
view of the U.S. Committee.
The Global Weather Experiment
1. The Observational Phase Through the First Special Observing Period
R. J. Fleming, T. M. Kaneshige, and W. E. McGovern
United States Project Office for the First GARP Global Experiment,
NOAA, Rockville, Md. 20852
Abstract
An unprecedented analysis of the atmosphere of planet Earth
is currently underway with the involvement of over 140
countries in the Global Weather Experiment—the largest
international scientific experiment yet attempted. After
many years of planning, the Operational Year began in
December of 1978. Following the field phase and data manage-
ment phase, a multi-year evaluation and research program
will commence and continue until the late 1980s. During this
period, scientists and technicians will examine the atmosphere,
the sea surface, and the upper layer of the world's oceans in
the most intense survey and study ever made. A number of
successes and failures occurred in preparing for the observing
phase and these are mentioned as each observing system
actually deployed in the field is reviewed. The focus of the
paper is on the quantity of data gathered and how it was
obtained. The article concludes with some suggestions for
assurances of final success of the Experiment.
1. Introduction
The year of 1979 has been a banner year in the monitor-
ing and understanding of the atmosphere of three
planets in our solar system. There have been probes
of Venus, quantitative measures of vortex systems on
Jupiter, and an unprecedented analysis of the atmo-
sphere of planet Earth. This latter activity involves the
efforts of over 140 countries in the Global Weather
Experiment—the largest international scientific experi-
ment yet attempted.
0003-0007/79/060649-ll$06.75
© 1979 American Meteorological Society
Bulletin American Meteorological Society
FGGE1, now termed the Global Weather Experiment,
was officially suggested as a GARP program over 10
years ago. After many years of planning and the com-
pletion of a one-year buildup phase of national and
international systems tests, the Operational Year began
in December 1978. Two Special Observing Periods
(SOPs) have been planned within this year: January-
February (SOP-I) and May-June (SOP-II). Following
the field phase and data management phase, a multi-
year evaluation and research program will commence
and continue until the late 1980s. During this period,
scientists and technicians will examine the atmosphere,
the sea surface, and the upper layer of the world's
oceans in the most intense survey and study ever made.
The purpose of this brief article is to provide a
progress report on the Global Weather Experiment
from the beginning of the Operational Year (1 Decem-
ber 1978) until the present (15 March 1979). There have
been a number of successes and failures in preparation
for the observing phase. Some of these will be mentioned
as we review each of the observing systems actually
deployed in the field. Because most of the data collected
from these observing systems can only be fully evalu-
ated in a delayed time mode, it is clearly too early to
1 FGGE is the acronym for First GARP (Global Atmo-
spheric Research Program) Global Experiment. GARP is a
highly successful joint program of the World Meteorological
Organization (WMO) and the International Council of
Scientific Unions (ICSU).
649
650 Vol. 60, No. 6, June 1979
TABLE 1. Average daily number of surface and upper-air observations
during initial phase of the experiment
Surface
Land stations Ocean stations*
Upper-air
Land and
ocean stations Aircraft
Early operational
year (Dec. 1-Jan. 4)
SOP-I
Intensive period
40 335
39 433
39 405
2 759
2 982
3 059
2 704
2 748
2 776
4 420
4 847
4 949
* Ocean Weather Stations, roving vessels, and stationary buoys.
tell if the critical mass of quality data needed to achieve
the objectives2 of the Experiment has been captured.
Our focus in this paper is to illustrate the quantity of
data gathered as best we know it at this time, and to
indicate how it was obtained.
In view of the enormous amount of data collected
by different observing systems over the entire globe,
the many countries involved, and the importance of a
completely quality-controlled data set, the main body
of FGGE research observations (Level Il-b data)3 will
not be available until at least 6 months after the time
of the observations. Thus, the complete statistics are
not yet available on any of the systems. In order to
prepare this article on a timely basis as suggested by
the United States Committee for the GARP, it will be
necessary to append to our remarks a caveat on each
system as appropriate.
We should perhaps remind ourselves that while
modern man has been breathing this envelope of air
we call our atmosphere for the past several hundred
thousand years, it has been less than a half century
(with the mass production and use of the radiosonde)
since he began to systematically probe its 3-dimen-
sional structure. Observing this global gas remains a
logistical nightmare, demands an enormously expensive
operation, and is still subject to many types of errors.
Measured in absolute terms, the prospect of fully
observing the atmosphere appears remote. Nevertheless,
in the Global Weather Experiment the nations of the
world have compromised their political differences to
alleviate the logistical problems, pooled their resources
to provide a whole greater than the sum of the parts,
and committed their scientists to investigate and reduce
those many sources of error. Measured relative to what
has occurred heretofore, the Experiment will perhaps
be viewed as a memorable milestone. Based upon the
2 The objectives of the Global Weather Experiment are
described in the National Academy of Sciences' document
listed in the references.
3 FGGE data are labelled as Level I, II, or III respectively
for raw data, observations, or analyzed data. The data are
further sublabeled as "a," "b," or "c" depending on whether
they pertain to data collected operationally in near-real-time,
collected in both real- and delayed-time to obtain the most
complete data set possible, or collected specially for climate
research.
successful completion of end-to-end tests and accounts
of several data producers, we are impressed and en-
thusiastic about the initial data volume and quality,
and we are cautiously optimistic about the expected
scientific return on this international investment.
2. World Weather Watch (WWW) systems
The timing of the Global Weather Experiment was
based upon the first-time availability of global coverage
from five geostationary satellites and a new third-
generation polar-orbiting satellite system. While the
satellites determined the timing, the foundation upon
which the Experiment was built was an improved
WWW. Implemented in 1967, the WWW consists pri-
marily of the surface and upper-air stations of the
member countries of the WMO, the mobile ship
stations, aircraft reports (AIREPS), and various
satellite observations that are currently exchanged in
real-time via the Global Telecommunication System
(GTS).
The growth of the WWW has been slow but steady.
For the Global Weather Experiment, many countries
have promised to improve their upper-air observations
and to provide complete reports in a delayed mode,
even if garbled or lost on the GTS. The results of this
delayed collection are not yet available. However,
Table 1 is a summary of the amount of WWW data
received at NOAA's National Meteorological Center
(NMC) during and just prior to SOP-I and an example
of a typical real-time collection (data files are closed
12 h after synoptic time of observation). Of particular
interest are the number of upper-air reports (radio-
sondes, rawinsondes, and pibals). On a typical day in
1977 this total was around 2000; it rose to approxi-
mately 2200 in July of the Build-Up Year, and in-
creased to approximately 2700 per day during SOP-I.
Because of the importance of measuring the wind
field in the tropics, the United States temporarily
implemented four upper-air stations in the equatorial
Pacific for the SOPs. These stations are located at
Enewetak (11.4°N, 162.4°W), Woleai (7.4°N, 143.9°E),
Kapingamarangi (1°N, 154.8°E), and Canton (2.8°S,
171.7°W). Observations were made at 0000 and 1200
GMT. In addition, the station at Fanning (3.9°N,
159.4°W), which had been temporarily implemented
for the North Pacific Experiment (NORPAX) on a
Bulletin American Meteorological Society 651
six per week observational schedule, was augmented
to a two per day schedule throughout the SOP. Seven
other U.S. stations, located within the 10°N-10°S zone
and part of the World Weather Watch basic observing
network, were also augmented from one observation
per day to two observations per day during the SOP
(Ascension, Diego Garcia, Truk, Ponape, Majuro,
Koror, Yap).
Implementing and operating these remote island
stations, which have been inactive since WW II, was
a challenging task. The range of performance of the four
new stations was as follows: Enewetak (120 observa-
tions expected) provided 108 soundings of which 108
reached 500 mb, 100 reached 100 mb, and 93 reached
70 mb or higher. Eleven of the missing observations
were due to equipment damage from Typhoon Alice.
Woleai (120 soundings expected) provided 57 soundings
of which 57 reached 500 mb, 47 reached 100 mb, and
39 reached 70 mb or higher. Sixty of the missing 63
observations were due to the near-simultaneous failure
of both the primary and backup generators, requiring
evacuation of the site 30 days early. The lack of
adequate transportation in this remote part of the globe
prevented a timely replacement.
Several other countries added new or temporary
upper-air stations for the Global Weather Experiment
and/or the associated regional experiments. Some of
these were in developing countries with resources
provided by developed countries through the WMO's
Voluntary Assistance Program. We anxiously await
the final tally on the overall performance of the WWW.
3. Satellite systems
In addition to the normal contribution of the 147
member countries of WMO, all of whom participate
actively in the WWW, 70 of these members plus five
intergovernmental organizations are making additional
contributions to the Global Weather Experiment and
the associated regional experiments. These additional
resources include funds, equipment, and personnel
needed to implement the necessary special observing
systems and data management systems required to
make the Experiment a success. In this and in following
sections, we will indicate the status of the space-based
portion of the WWW and the special observing systems.
a. Geostationary satellites
A system of five geostationary satellites has been
strategically placed around the Equator and serves as
a vital part of the composite observing system for the
Global Weather Experiment. The location of these satel-
lites is indicated in Fig. 1. Three of these (provided by
Japan (GMS), the European Space Agency (METEO-
SAT), and the United States (GOES-Indian Ocean))
were launched and/or positioned primarily to support
the Experiment. In addition to the many scales of
motion that are discernible from the sequences of
images obtained from these satellites, one can also
obtain cloud-motion vectors from successive visible and
IR images. These satellites provide an indication of the
wind field in an area of approximately 50° from the
satellite subpoint. Winds are deduced for two or three
levels. These cloud-motion vectors are especially
valuable near the equator where there are relatively
few land stations and where knowledge of the wind
field is so essential.
The United States has maintained two geostationary
satellites under simultaneous operation for several
years. These have been systems from the Synchronous
Meteorological Satellite (SMS) and Geostationary
FIG. 1. Geostationary satellite coverage during the Global Weather Experiment.
652 Vol. 60, No. 6, June 1979
Operational Environmental Satellite (GOES) series.
During the Operational Year GOES-3 or GOES-West
(at 135°W) has been operating flawlessly. However,
GOES-2 or GOES-East (at 75°W) experienced early
problems with the precision latitude stepping mecha-
nism of the Visible and Infrared Spin Scan Radiometer
(VISSR). This problem caused a foreshortening of
pictures with coverage lost south of 35°S latitude after
28 December.
Since further degradation of GOES-2 was anticipated
(and actually occurred on 12 January when data were
lost south of the Equator), SMS-1, an older backup
satellite already in orbit, was moved slowly eastward
by NOAA's National Environmental Satellite Service
(NESS) from its standby position (92°W on 9 January)
to 75°W on 26 January. On that date GOES-2 imaging
operations were terminated and SMS-1 became known
as GOES-East. However, as SMS-1 was moving east-
ward from 16 January-26 January, sufficient southern
hemisphere images were taken to provide winds twice a
day over the otherwise missing data area. These SMS-1
images were transmitted to the Space Science and
Engineering Center (SSEC) at the University of
Wisconsin through GOES-2, where winds will be
subsequently processed. As a result of these back-up
operations, the only data lost will be over the area of
the southern hemisphere covered by GOES-2 from 12
January through 15 January.
NESS normally produces wind vectors three times a
day (00 GMT, 12 GMT and 18 GMT). In January and
February, GOES-West and GOES-East (SMS-1 and
GOES-2) provided 41 285 and 39 954 wind vectors
respectively. Unless there are further complications,
these monthly totals should be around 45 000 with a
horizontal resolution of between 250-500 km.
In order to take full advantage of the high resolution
visible image data of the GOES satellites, arrangements
have been made to capture a full digital archive via
two antenna systems on top of the SSEC building at the
University of Wisconsin. SSEC personnel are providing
a mesoscale tropical wind data set from GOES-West
and GOES-East. The wind fields will be available for
the entire Operational Year and are defined between
15°N and 15°S. The number of wind vectors produced
for January and February are 38 758 and 39 060
respectively, and have a resolution of between 100-200
km. We hasten to point out that the volume of winds
is not so important as the quality. Steps have been
taken so that winds provided by all satellite operators
are also tagged with a quality control indicator for use
in optimal interpolation analysis methods; e.g., see
Bergman (1979).
Japan launched its first geostationary satellite in the
summer of 1977. Located at 70°E, the satellite provides
a unique view of atmospheric events in that part of
the globe including the winter monsoon. Sea-surface
temperatures (SST) are derived from this satellite, and
during the first three months of the Experiment over
41 000 10-day mean SSTs were obtained. Also during
this time period between 146 and 499 wind vectors per
day were obtained with a daily mean of over 300.
Efforts are underway to obtain a complete digital
archive of the Japanese satellite data to be located at the
University of Wisconsin. Coupled with digital data
obtained from the other satellites during this Experi-
ment, this will be a unique data source available to all
users for stereowind development techniques and other
downstream research applications.
The European Space Agency (ESA) launched its
first geostationary satellite in the fall of 1977. This
satellite, located at 0° longitude, began production of
twice daily winds on 15 November 1978. During
January and February, 24 727 and 25 997 wind vectors
were obtained, respectively. In addition to the visible
and IR channels common to all the geostationary
satellites, ESA's Meteosat has water vapor images
from the 5.7-7.1 jum channel data (cf., Morel et al.,
1978). These unique images promise to offer new
insights into various atmospheric processes.
The fifth geostationary satellite was to come from
the USSR. But when it was announced that this
satellite would be late, an alternate backup plan was
immediately implemented with funds provided by
NASA, NOAA, and NSF. GOES-1 (a satellite already
in orbit with certain systems inoperative but with a
working VISSR) was moved to 58°E to fill the Indian
Ocean area—both to benefit the Global Weather
Experiment and the Summer Monsoon Experiment.
Since the United States could then only operate two
of these geostationary satellites simultaneously, imple-
mentation of the third satellite over the Indian Ocean
area was a cooperative effort between ESA and the
United States. The data are obtained by an ESA
receiving station at Villafranca, Spain. The antenna,
certain ground equipment, and personnel needed for
system installation and integration were provided by
the United States. ESA is providing ground equipment,
personnel, and other support to operate the system 24 h
a day. The data are stored on a new video cassette
system developed by the SSEC. This is a modified
video cassette system that is capable of recording
approximately 10 full resolution images on a standard
cassette.
SSEC personnel are processing the data from Spain
and are providing winds in the Indian Ocean area in a
delayed mode. During December there were 46 816
winds produced. The images provided by this satellite
are unique and excellent. Arrangements have been
made to have some of these images available in real-time
in Europe and Africa. The United States satellites have
a spin-scan camera that rotates at a rate of about 100
rotations per minute. Since only 5% of each rotation
is occupied with taking and transmitting the data
to Villafranca, during the rest of each rotation the
data are retransmitted ("stretched") to the satellite,
which then relays the data at lower bandwidth to
simpler equipped receiving stations. One such station
is in Lannion, France, which can then retransmit the
data through the ESA satellite. Figure 2 shows that
the data are retransmitted from Spain to the ESA
satellite and then to users in Europe and Africa with
Meteosat compatible receivers.
Bulletin American Meteorological Society 653
FIG. 2. Operational data flow for GOES—Indian Ocean.
b. Operational polar orbiting satellites
TIROS-N, the first of the third generation weather
satellites, was launched on 13 October 1978. The satellite
was placed into a near-polar, sun-synchronous orbit
with an inclination of 98.9° and at an average altitude
of 854 km in contrast to 1511 km for the second gener-
ation NOAA-5. The orbital period is 102 min, permitting
TIROS-N to complete just over 14 orbits per day. The
second satellite in this series, NOAA-A, was expected
to be launched by late June 1979 into a slightly lower
orbit (833 km). In the operational configuration, the
two satellites will be positioned with a nominal orbital
plane separation of 90°. TIROS-N crosses the Equator
in an afternoon 1500 local solar time (LST) ascending
orbit; NOAA-A will cross in a morning 0730 LST
descending orbit.
Instruments on TIROS-N include the Advanced
Very High Resolution Radiometer (AVHRR) and the
TIROS Operational Vertical Sounder (TOVS), which
in turn includes the High Resolution Infrared Sounder
(HIRS/2), the Stratospheric Sounding Unit (SSU),
and the Microwave Sounding Unit (MSU). Also aboard
the satellite is the Data Collection and Platform
Location System (the French-built ARGOS system), a
random access system capable of platform location as
well as data collection from both moveable and fixed
platforms, such as buoys and balloons.
The launch of TIROS-N was delayed several times
but fortunately its postponement, while causing great
consternation and apprehension, has not greatly
affected the Experiment. The then operational satellite,
NOAA-5, continued to supply data for the Experiment
until corresponding data became operational from
TIROS-N. A heroic effort by satellite technicians
saved TIROS-N from a critical tumbling mode early
in its lifetime. This occurred before any substantial
adverse impact on the southern hemisphere drifting
buoy launch and check-out operations.
The TOVS on TIROS-N is substantially more
sophisticated than the VTPR of NOAA-5. Not only is
there greater vertical resolution and a finer resolution
scan geometry, but the microwave channels allow more
soundings to be computed over cloud-contaminated
areas. Atmospheric temperature profiles amounted to
slightly less than 1000 per day using NOAA-5/VTPR
for the months of December 1978 and January 1979.
In contrast the TIROS/HIRS system, which became
operational on 28 February 1979, produced about
52 000 temperature soundings with an associated
resolution of 250 km during the first seven days of
March. TIROS-N soundings from 1 January-28
February are being processed in a delayed mode and
will subsequently be incorporated into the FGGE
Level Il-b data base. The accuracy of these data
vis-a-vis radiosondes is being examined now by NESS
and NMC.
In December, with use of the NOAA-5 Vertical
Temperature Profile Radiometer (VTPR), 4660 sea-
surface temperature (SST) observations were obtained
daily. In January, using the TIROS-N/AVHRR system
over 1 million SST observations were obtained, approxi-
mately 39 000 per day. The spatial resolution of the
TIROS-N SST is 50 km.
The ARGOS data collection system on the TIROS-N
satellite has been working extremely well. In addition
654 Vol. 60, No. 6, June 1979
to the data processing of drifting buoy and constant
level balloon information, France has been distributing
these data over the GTS four times a day. For example,
the buoy data are sent from Toulouse, France, about 3 h
40 min after each synoptic hour and received in Mel-
bourne, Australia, approximately 2 h and 20 min later
where real-time monitoring is performed.
On 25 January, the USSR launched a new satellite
in the Meteor series with a spectrometer-interferometer
onboard. At the present time, the quality of temperature
soundings from this system is being evaluated and
they are expected to be included in the FGGE data set.
c. Research satellites
There were two research satellite systems planned by
NASA that were not funded directly as FGGE
systems but for which provisions were made to obtain
a portion of the data for the Global Weather Experi-
ment. The first of these satellite systems was
SEASAT-A.
The primary aim of the SEASAT program is to
evaluate the effectiveness of remotely sensing oceano-
graphic and related meteorological phenomena from a
satellite-borne platform in space. SEASAT-A was the
first of a series of satellites of this program. However,
it ceased functioning on 10 October 1978 after 99 days
of operation. The ocean surface wind fields anticipated
from the SEASAT-A Scatterometer System (SASS)
will therefore not be available during the Operational
Year. No significant quantities of data from the SASS
or other sensor systems on SEASAT for this 99-day
period will be available until mid to late 1979.
The second satellite system called Nimbus-7 (re-
ferred to as Nimbus-G prior to launch) was successfully
launched on 24 October 1978 into a sun-synchronous,
near-polar orbit. All instrument systems have con-
tinued to function in a nominal fashion and these are
discussed briefly below.
The Scanning Multi-Channel Microwave Radiometer
(SMMR) continued to operate in a 1-day on, 1-day
off cycle throughout SOP-I. The Level Il-b products
to be derived from the SMMR include continuous
along-track measurements of sea surface temperature,
sea surface wind speed, and total atmospheric water
vapor. The Level II-c products will include monthly
mean ocean rain rates and 3-day sea ice concentration
composites. Because of the delays encountered in
obtaining the software required to incorporate the
appropriate antenna pattern corrections, validated
SMMR products are not likely to be available until
the fall of 1979. The intended Level Il-b products will
therefore become part of the Supplementary Level
Il-b data set.
The Limb Infrared Monitor of the Stratosphere
(LIMS) lifetime is estimated at 7 months due to the
limited life of the solid cryogen cooler. Due to this
limited lifetime and a mechanical interference between
the LIMS and the scanning modes of the Earth Radia-
tion Budget experiment, a compromise was reached
that allows the LIMS to operate in an effective 62%
on-duty cycle. The LIMS data is being processed to
yield stratospheric temperature profiles (10-65 km)
at approximately 320 km intervals along the satellite
track. Approximately 32 000 profiles are generated
during a month's time. These Level Il-b data sets will
be forwarded to the data collection center in Sweden.
The Earth Radiation Budget (ERB) instrument is
being operated in a 3-day on, 1-day off duty cycle with
the scanning modes being used during 50% of the on
times. The use of the scanning modes will return to
nearly 100% once the LIMS instrument becomes in-
operative. The Level II-c products to be derived from
ERB include daily values of total and spectral solar
irradiance as well as monthly mean maps of earth
albedo, net radiation, and longwave flux. The Solar
Backscatter Ultraviolet and Total Ozone Mapping
Spectrometer (SBUV/TOMS) is being operated in a
5-day on, 1-day off duty cycle. Interim Level II
products are being produced on a limited basis and
look very promising. The Level II-c product to be
derived from the TOMS will be daily global mappings
of total ozone amount.
4. Tropical wind systems
When it was determined that a United States system
of carrier balloons would not likely achieve the obser-
vational requirements of the Experiment, greater
emphasis was placed on existing wind-determining
systems in the tropics and on several new systems.
Additions to the WWW land stations, satellite winds,
and conventional AIREPS provided tropical wind
measurements and were discussed above. Other systems
providing tropical wind measurements are described
below.4
a. Aircraft Dropwindsonde Program
The Aircraft Dropwindsonde Program provides a
significant portion of the direct observations of vertical
wind profiles required in the equatorial tropics. During
the Intensive Period, the United States dropwindsonde
aircraft flew on six long-range tracks from four tropical
bases (Hawaii, Panama, Ascension Island and Diego
Garcia Island) as seen in Fig. 3. Slightly different
tracks were flown on a daily basis in order to avoid
convective activity, the taking of nonrepresentative
soundings, and any unnecessary overlap with ships.
Coordination of ship positions and potential aircraft
tracks was achieved by communication with the FGGE
Operations Center in Geneva, Switzerland.
Aircraft tracks in the Atlantic and Pacific Oceans
were flown at an average altitude of 13 km covering
a range of approximately 8000 km. Aircraft tracks in
the Indian Ocean were flown at an average altitude of
9 km covering a range of approximately 6500 km.
Dropwindsonde observations (sondes descending by
4 A more detailed summary of various systems and tech-
niques for determining winds during the Global Weather
Experiment is provided in Atmospheric Technology, Number
10, Winter 1978-79, National Center for Atmospheric Re-
search, Boulder, Colo.
Bulletin American Meteorological Society 655
FIG. 3. Aircraft dropwindsonde tracks flown during first intensive period.
parachute from the aircraft) were made along the
tracks at 350 km intervals and included vertical
profiles of wind, temperature, and humidity. The
dropsonde package contained an Omega navigation
receiver/transmitter from which winds are derived
(see Tropical Wind Observing Ship discussion below).
During the first week of aircraft operations, numerous
operational problems occurred. Therefore, the 30-day
Intensive Period (originally starting on 15 January)
was extended an additional 7 days. Due to a series of
mechanical failures and the need to divert U.S. Air
Force aircraft for other high priority missions, only 11
sorties were flown from Ascension with 205 sondes
launched and 74% successful.
Operations at other locations were far more successful
(Panama, 31 sorties, 530 sonde launches, 91% success-
ful; Hawaii, 70 sorties, 1210 launches, 91% successful;
and Diego Garcia, 59 sorties, 868 launches, 86%
successful).
b. Tropical Wind Observing Ships {TWOS)
Strategic ocean gaps in the tropics not covered by the
aircraft tracks, WWW land stations, or island stations
were filled by some 40 oceanographic research vessels
classified as Tropical Wind Observing Ships (TWOS).
These ships provided twice daily vertical profiles of
wind, temperature, and humidity. Some of these ships
were dedicated to the Experiment as TWOS, while
others provided the atmospheric measurements as a
secondary mission to their primary oceanographic
activities.
Ten USSR ships had radar wind-finding systems on
stabilized platforms. Five additional ships (from France
and the Federal Republic of Germany) employed wind-
finding systems similar to those used in the GARP
Atlantic Tropical Experiment (GATE). The remaining
ships (from Brazil, Canada, Peoples Republic of China,
Hong Kong, Indonesia, Italy, Mexico, Peru, Philippines,
Senegal, USSR and the USA) used a new WMO-
furnished "record-only" NAVAID sounding system
consisting of radiosondes carrying temperature, pres-
sure (i.e., for height determination), and humidity
sensors as well as a low frequency Omega receiver and
transmitter. The signals transmitted by land-based
Omega stations are intercepted by the sondes, relayed
back to the ship, and recorded on cassette tapes. In the
final processing at a centralized facility, the position
of the sonde can be determined. Horizontal wind speed
and direction can then be computed by measuring the
displacement of the ascending sonde.
The WMO system was funded by contributions from
Saudi Arabia, the United States, the United Nations
Development Program, and the United Nations
Environmental Program. Finland agreed to provide
the delayed processing of the data for the Experiment.
This system was designed to provide a greater return
656 Vol. 60, No. 6, June 1979
FIG. 4. Areas of minimum (dashed line) and maximum (solid line) balloon coverage during
the period 7 January-28 February 1979.
of data (although with less skilled operators and main-
tenance people onboard) than the real-time GATE
shipboard system. The system did achieve this goal. A
preliminary check with the TWOS NAVAID Data
Center in Finland revealed that while there were some
balloon launch problems on two ships, 90-95% of the
thermodynamic and wind data recorded would be
recovered. Over 1300 cassettes (one per sounding) had
been mailed to Finland by mid-March.
Data from non-NAVAID ships are sent to the TWOS
(Radar) Data Center in the USSR. The results from
this center are not yet available; however, because of
the nature of ship operations, the final processed data
from both the TWOS centers are expected to be the last
available from all of the FGGE observing systems.
During SOP-II and for the Summer Monsoon Experi-
ment, additional ships from 22 countries are expected to
be providing upper-air measurements.
c. Tropical Constant Level Balloons (TCLB)
Above the ships and aircraft, at approximately 14 300
m, constant density balloons provided measurements
of wind and temperature. During the period of 6
January-3 February, 153 balloons were launched by
scientists of the National Center for Atmospheric
Research (NCAR) from Canton Island in the Pacific
and from Ascension Island in the Atlantic. While the
balloon lifetimes did not meet the expected value,5 a
wealth of data has been gathered in the upper levels
of the tropical troposphere. For example, the delayed
processing of these data will provide over 3600 wind
vectors in the region south of 25° North latitude
between the time period of 5 January-5 March. In the
region between 10°N and 10°S, an average of 70 wind
vectors per day will be obtained during the Intensive
Period of 15 January-20 February. Many of these
winds were processed in real-time, e.g., during the 24 h
period ending 12 February, 83 winds were received on
the GTS from 56 operational balloon platforms. The
delayed processing will provide at least two winds per
day from each platform and these data will supplement
the tropical wind field information obtained from the
other tropical wind measuring systems.
5 The actual performance is still being analyzed by the
scientific team at NCAR as some platforms are still circum-
navigating the globe at this writing.
The circulation of the upper tropical troposphere is
far from simple. Figure 4 gives a relative measure of
balloon distribution in the zone of 30°N-50°S, over the
time period of 7 January-28 February. Only two
contours are shown: the dashed areas where no balloons
were reported during the period and the solid areas
where greater than 20 balloon locations were made
during the period. We leave the discussion of the distri-
bution to the TCLB scientific team (to appear in a later
article) and merely point out here that virtually the
entire area is partially covered, with two notable areas
of no coverage (north of the Equator in the Atlantic
and south of the Equator in the Indian Ocean and
Indonesian areas). There are also areas of clustering
around and downstream (eastward) of the launch sites:
Canton Island (2°S, 171°W) and Ascension Island
(8°S, 14°W). Arrangements for a third launch site
are underway, which, it is hoped, will alleviate the
coverage gap in the Indian Ocean and Indonesian areas.
A tremendous amount of information has been
obtained on the tropical wind field from the composite
of observing systems: the WWW land and island
stations, the conventional and automated AIREPS, the
satellite winds from five geostationary satellites, the
aircraft dropwindsonde system, the Tropical Wind
Observing Ships, and the constant level balloons. We
anxiously await the research results that should emerge
from this unprecedented data set.
5. Southern hemisphere drifting buoys
The small proportion of land to ocean area and the low
ship traffic in the southern hemisphere results in com-
paratively few surface observations from this region.
However, "reference level" measurements, in particular
surface barometric pressure measurements, are im-
portant for maximum utilization of information from
the satellite observations. To meet this need, eight
countries (Australia, Canada, France, New Zealand,
Norway, South Africa, United Kingdom, and United
States) have contributed over 300 drifting buoys to
the Experiment. Equally important, 14 countries
(Argentina, Australia, Brazil, Canada, Chile, Federal
Republic of Germany, France, Japan, New Zealand,
Norway, South Africa, United Kingdom, United States,
and USSR) agreed to deploy strategically these buoys
over the southern hemisphere oceans. These buoys are
Bulletin American Meteorological Society 657
FIG. 5. Location of operational drifting buoys in the southern hemisphere on 15 February 1979.
being designed to monitor surface atmospheric pressure
and sea-surface water temperature to within ±1 mb
and ±1°C, respectively.
The international plan called for the deployment of
these buoys south of 20°S with a spacing of approxi-
mately 1000 km. Ideally, this would require only 147
buoys, but due to the very complex and expensive
real-world deployment problem (requiring the use of
piggy-back Antarctic resupply support, available com-
mercial shipping, and dedicated deployers as could be
financed), the plan was to deploy as many as physically
possible through the first SOP and then reseed the
buoy array between SOPs. By 15 January there were
147 buoys launched and 126 operational. By 12 Febru-
ary there were 193 launched and 165 operational.
Figure 5 provides a snapshot view of the buoy's posi-
tions as of 15 February.
The reseeding of the buoy array began early in the
year and was scheduled through the first week of May.
The United States has added an additional 12 buoys
to 6 previously available for reseeding, and these 18
were scheduled to be air-dropped in late April and early
May to fill specific gaps.
The drifting buoy data is received via the ARGOS
collection and location system aboard the TIROS-N
satellite and is relayed to France through United States
ground stations for processing and insertion onto the
GTS. In view of the many modes by which these buoys
can fail (enroute to launch, at launch, through ocean
environment factors, electronics failures, etc.) we are
extremely pleased with the success ratio and feel that
the drifting buoy technology has finally arrived as a
cost-effective observing system. With the help of this
vastly improved surface pressure data base, the 3-
dimensional structure of the southern hemisphere
should be revealed as never before.
6. Automated aircraft reports
Manually determined and communicated weather
information is currently available from certain com-
mercial aircraft. These are included in the WWW
totals listed in Table 1. However, the Global Weather
Experiment will benefit from a special effort by The
Netherlands in processing delayed but automated data
from several countries' commercial carriers that provide
very accurate wind and temperature information.
These carriers have about 80 aircraft (subsets of the
DC-10, B-747, and Concorde fleets) equipped with
Aircraft Integrated Data Systems (AIDS) that re-
cord meteorological and engineering data on cassette
658 Vol. 60, No. 6, June 1979
recorders. These data will come from worldwide
routes and be very valuable to the Experiment.
AIDS countries (airlines) provided over 60 000 wind
and temperature reports in the month of January and
included Denmark/Sweden/Norway (SAS), Nether-
lands (KLM), Switzerland (Swiss Air), Thailand (Thai
International), United Kingdom (British Airways),
United States (TWA) and Venezuela (VIASA). This
number should vary between 60 000 and 90 000 per
month for the Experiment.
A real-time system of obtaining accurate wind and
temperature information from wide-bodied jets
equipped with inertial navigation systems has also
been developed for the Experiment. This system is called
Aircraft to Satellite Data Relay (ASDAR). About 17
aircraft will have the capability to send data in real-time
(eight reports sent every hour) via the data collection
system on board the geostationary satellites. This
system, developed by NASA and NOAA, will be tested
in a quasi-operational mode during the Global
Experiment.
While the data (winds and temperatures) from this
new system are extremely accurate, the system is
behind schedule due to a variety of small but limiting
problems. Only five ASDAR units have flown at any
one time during SOP-I. However, by mid-March the
number has risen to 10: Pan American (1), SAS (1),
Singapore International (3), United States Air Force
(1), QANTAS (4). It is expected that the operational
version of ASDAR will become a significant global
observing system of the future WWW.
Another real-time system is being developed and
tested for use over the United States. This is a NOAA
effort in cooperation with American Airlines to provide
real-time data through the new fully automated VHF
communications system of Aeronautical Radio Inc.
(ARINC). This system, called ARINC Communica-
tions Addressing and Recording Systems (ACARS),
complements ASDAR and also has far reaching possi-
bilities for improved benefits to the airlines and the
weather services for the short-range prediction problem.
The coverage is limited now to just the continental
United States and surrounding waters. This system with
the meteorological terminal attached is capable of
providing a report every 3.75 min (transmitted in
real-time as a group of six reports every 22.5 min) in
the high density mode. At typical aircraft speeds, this
corresponds to a resolution of about 56 km. The first
ACARS units with the meteorological terminal at-
tached will fly during SOP-II and eventually 11 units
will be flying through mid-1980 in this first test of the
system. ACARS will also help provide error statistics
for several of the other FGGE observing systems.
7. Oceanographic and regional experiments
A coordinated ocean program associated with the
Global Weather Experiment provides an unprecedented
opportunity for large-scale monitoring and research
aimed at improving our understanding of coupled
atmosphere-ocean interactions. To that end, SCOR
(ICSU/Scientific Committee on Ocean Research)
Working Group 47 has taken the responsibility of
coordinating oceanographic activities in the Atlantic,
Pacific, and Indian Oceans. This short paper cannot
adequately describe the observational programs. How-
ever, the field phase of various programs has begun
primarily in the three tropical oceans and includes
ship-based measurements, bottom-mounted sensors,
drifting and drogued buoys, real time BATHY-
TESAC reports, XBTs from ships of opportunity,
AXBTs, etc. A comprehensive summary of the planned
implementation of these systems is given in the Oceano-
graphic Programme for the FGGE.6
In view of the normal time required to complete
oceanographic operation, it will be some time before
an assessment can be made of their status. Most of the
oceanographic data will be available to the research
community via the Level II-c data set two years after
the valid time of the data. The principal atmospheric/
oceanic objectives are 1) to provide information on the
sea-surface temperatures and on the ocean's "mixed
layer" structure in order to develop parameterization
techniques for including oceanic influences in atmo-
spheric models, and 2) to obtain oceanographic data
permitting more definitive studies of ocean responses
to atmospheric influences, especially in the equatorial
regions.
Several specialized experiments having to do with
significant regional phenomena (Asian monsoons,
West-African monsoons, and the polar regions) are
important elements of the Global Weather Experiment.
The principal regional experiments have their own
scientific aims but will provide detailed data for the
Global Weather Experiment and will benefit, in turn,
from the improved global data set provided by the
Global Weather Experiment since the regional phe-
nomena are inextricably linked with the global circu-
lation. Many countries are involved in these regional
experiments. The United States is providing observing
systems in the West Arabian Sea, the Bay of Bengal,
the South China Sea, and the polar regions. Reports
of these regional experiments will be forthcoming from
those principal investigators involved in the Winter
Monsoon Experiment (MONEX) (Greenfield and
Krishnamurti, 1979), Summer MONEX, West African
MONEX (WAMEX), and the Polar Experiment
(POLEX).
8. Conclusion
A review of all the observing system programs is in
progress and a number of changes have been or will be
implemented before SOP-II; e.g., the troublesome
WC-135s (two planned for operations but only one
available) in the Atlantic Dropwindsonde program
will be replaced with two C-141s, a third launch site is
planned for the Tropical Constant Level Balloons, and
6 The Global Weather Experiment Implementation/Opera-
tions Plan, Vol. 7, Oceanographic Programme for the FGGE,
World Meteorological Organization, Geneva, December 1978.
Bulletin American Meteorological Society 659
more back-up generators will be placed on the remote
island stations.
Sometimes it is appropriate to state the obvious:
while the data volume collected so far appears im-
pressive, the success of the Global Weather Experiment
will depend upon the creative talents of the research
community in applying these data and/or their ideas
to achieving the scientific goals. Interested participants
in the research phase can view a preliminary film7 on
the Experiment, refer to a recent National Academy
of Science publication on the research opportunities
(U.S. Committee for GARP, 1978), and watch for a
future GARP Topics article which will supply detailed
procedures for submitting proposals to the various
funding agencies that will be supporting the research
phase of the Experiment through the 1980s.
7 A 14-min color film entitled "The Global Weather Experi-
ment—A Whole Earth View" is available by writing to:
Motion Picture Service, U.S. Department of Commerce,
NOAA, 12231 Wilkins Avenue, Rockville, Md. 20852.
Acknowledgments. A great many scientists, engineers and
administrators from many countries have contributed to the
Global Weather Experiment planning and implementation
through the years. It is not possible to mention all of these by
name. However, one must highlight the efforts of Professor
Bo Doos and the staff of the GARP Activities Office within
the WMO in keeping things on track through occasionally
difficult times.
References
Bergman, K. H., 1978: Role of observation errors in optimum
interpolation analysis. Bull. Am. Meteorol. Soc., 59, 1603-
1611.
Greenfield, R. S., and T. N. Krishnamurti, 1979: The winter
monsoon experiment—Report of December 1978 field phase.
Bull. Am. Meteorol. Soc., 60, 439-444.
Morel, P., M. Desbois, and G. Szejwach, 1978: A new insight
into the troposphere with the water vapor channel of
Meteosat. Bull. Am. Meteorol. Soc., 59, 711-714.
U.S. Committee for the Global Atmospheric Research Pro-
gram, 1978: The Global Weather Experiment—Perspec-
tives on its implementation and exploitation. National
Academy of Sciences, Washington, D.C., 104 pp.
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