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A.T.J. de Laat,
A. M. S. Gloudemans,
Schrijver H,
Aben I,
Nagahama Y,
Suzuki K,
Mahieu E,
N. B. Jones,
Paton-Walsh C,
N. M. Deutscher, [......],
Rinsland C,
A. V. Dzhola,
E. I. Grechko,
A. M. Poberovskii,
M. V. Makarova,
Mellqvist J, Strandberg A,
Sussmann R,
Borsdorff T,
Rettinger M
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a validation study of SCIAMACHY CO total column measurements from the IMLM algorithm using ground-based spectrometer observations from twenty surface stations for the five year time period of 2003–2007. Overall we find a good agreement between SCIAMACHY and ground-based observations for both mean values as well as seasonal variations. For high-latitude Northern Hemisphere stations absolute differences between SCIAMACHY and ground-based measurements are close to or fall within the SCIAMACHY CO 2σ precision of 0.2×1018 molecules/cm2 (~10%) indicating that SCIAMACHY can observe CO accurately at high Northern Hemisphere latitudes. For Northern Hemisphere mid-latitude stations the validation is complicated due to the vicinity of emission sources for almost all stations, leading to higher ground-based measurements compared to SCIAMACHY CO within its typical sampling area of 8×8°. Comparisons with Northern Hemisphere mountain stations are hampered by elevation effects. After accounting for these effects, the validation provides satisfactory results. At Southern Hemisphere mid- to high latitudes SCIAMACHY is systematically lower than the ground-based measurements for 2003 and 2004, but for 2005 and later years the differences between SCIAMACHY and ground-based measurements fall within the SCIAMACHY precision. The 2003–2004 bias is consistent with a previously reported Southern Hemisphere bias based on comparisons with MOPITT CO and is currently under investigation. No other systematic spatial or temporal biases could be identified based on the validation presented in this paper. Validation results are robust with regard to the choices of the instrument-noise error filter, sampling area, and time averaging required for the validation of SCIAMACHY CO total column measurements. Finally, our results show that the spatial coverage of the ground-based measurements available for the validation of the 2003–2007 SCIAMACHY CO columns is sub-optimal for validation purposes, and that the recent and ongoing expansion of the ground-based network by carefully selecting new locations may be very beneficial for SCIAMACHY CO and other satellite trace gas measurements validation efforts.
Atmospheric Measurement Techniques Discussions. 01/2010;
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A.T.J. de Laat,
A. M. S. Gloudemans,
Schrijver H,
Aben I,
Nagahama Y,
Suzuki K,
Mahieu E,
N. B. Jones,
Paton-Walsh C,
N. M. Deutscher, [......],
Rinsland C,
A. V. Dzhola,
E. I. Grechko,
A. M. Poberovskii,
M. V. Makarova,
Mellqvist J, Strandberg A,
Sussmann R,
Borsdorff T,
Rettinger M
[show abstract]
[hide abstract]
ABSTRACT: This paper presents a validation study of SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) carbon monoxide (CO) total column measurements from the Iterative Maximum Likelihood Method (IMLM) algorithm using ground-based spectrometer observations from twenty surface stations for the five year time period of 2003–2007. Overall we find a good agreement between SCIAMACHY and ground-based observations for both mean values as well as seasonal variations. For high-latitude Northern Hemisphere stations absolute differences between SCIAMACHY and ground-based measurements are close to or fall within the SCIAMACHY CO 2σ precision of 0.2 × 1018 molecules/cm2 (∼10%) indicating that SCIAMACHY can observe CO accurately at high Northern Hemisphere latitudes. For Northern Hemisphere mid-latitude stations the validation is complicated due to the vicinity of emission sources for almost all stations, leading to higher ground-based measurements compared to SCIAMACHY CO within its typical sampling area of 8° × 8°. Comparisons with Northern Hemisphere mountain stations are hampered by elevation effects. After accounting for these effects, the validation provides satisfactory results. At Southern Hemisphere mid- to high latitudes SCIAMACHY is systematically lower than the ground-based measurements for 2003 and 2004, but for 2005 and later years the differences between SCIAMACHY and ground-based measurements fall within the SCIAMACHY precision. The 2003–2004 bias is consistent with previously reported results although its origin remains under investigation. No other systematic spatial or temporal biases could be identified based on the validation presented in this paper. Validation results are robust with regard to the choices of the instrument-noise error filter, sampling area, and time averaging required for the validation of SCIAMACHY CO total column measurements. Finally, our results show that the spatial coverage of the ground-based measurements available for the validation of the 2003–2007 SCIAMACHY CO columns is sub-optimal for validation purposes, and that the recent and ongoing expansion of the ground-based network by carefully selecting new locations may be very beneficial for SCIAMACHY CO and other satellite trace gas measurements validation efforts.
Atmospheric Measurement Techniques. 01/2010;
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Dupuy E,
K. A. Walker,
Kar J,
C. D. Boone,
C. T. McElroy,
P. F. Bernath,
J. R. Drummond,
Skelton R,
S. D. McLeod,
R. C. Hughes, [......],
Urban J,
Vanhellemont F,
Vigouroux C,
T. von Clarmann,
P. von der Gathen,
C. von Savigny,
J. W. Waters,
J. C. Witte,
Wolff M,
J. M. Zawodny
[show abstract]
[hide abstract]
ABSTRACT: This paper presents extensive {bias determination} analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from nearly 20 satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the average values of the mean relative differences are nearly all within +1 to +8%. At higher altitudes (45–60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments, with mean relative differences of up to +40% (about +20% on average). For the ACE-MAESTRO version 1.2 ozone data product, mean relative differences are within ±10% (average values within ±6%) between 18 and 40 km for both the sunrise and sunset measurements. At higher altitudes (~35–55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (with mean relative differences down to −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS, indicating a large positive bias (mean relative differences within +10 to +30%) in the 45–55 km altitude range. In contrast, there is no significant systematic difference in bias found for the ACE-FTS sunrise and sunset measurements.
Atmospheric Chemistry and Physics 01/2009; · 4.88 Impact Factor
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Strong K,
M. A. Wolff,
T. E. Kerzenmacher,
K. A. Walker,
P. F. Bernath,
Blumenstock T,
Boone C,
Catoire V,
Coffey M,
M. De Mazière, [......],
Semeniuk K,
Senten C,
G. P. Stiller, Strandberg A,
Taylor J,
Tétard C,
Toohey M,
Urban J,
Warneke T,
Wood S
[show abstract]
[hide abstract]
ABSTRACT: The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar occultation technique. One of these instruments, the ACE Fourier Transform Spectrometer (ACE-FTS), is measuring volume mixing ratio (VMR) profiles of nitrous oxide (N<sub>2</sub>O) from the upper troposphere to the lower mesosphere at a vertical resolution of about 3–4 km. In this study, the quality of the ACE-FTS version 2.2 N<sub>2</sub>O data is assessed through comparisons with coincident measurements made by other satellite, balloon-borne, aircraft, and ground-based instruments. These consist of vertical profile comparisons with the SMR, MLS, and MIPAS satellite instruments, multiple aircraft flights of ASUR, and single balloon flights of SPIRALE and FIRS-2, and partial column comparisons with a network of ground-based Fourier Transform InfraRed spectrometers (FTIRs). Between 6 and 30 km, the mean absolute differences for the satellite comparisons lie between −42 ppbv and +17 ppbv, with most within ±20 ppbv. This corresponds to relative deviations from the mean that are within ±15%, except for comparisons with MIPAS near 30 km, for which they are as large as 22.5%. Between 18 and 30 km, the mean absolute differences for the satellite comparisons are generally within ±10 ppbv. From 30 to 60 km, the mean absolute differences are within ±4 ppbv, and are mostly between −2 and +1 ppbv. Given the small N<sub>2</sub>O VMR in this region, the relative deviations from the mean are therefore large at these altitudes, with most suggesting a negative bias in the ACE-FTS data between 30 and 50 km. In the comparisons with the FTIRs, the mean relative differences between the ACE-FTS and FTIR partial columns (which cover a mean altitude range of 14 to 27 km) are within ±5.6% for eleven of the twelve contributing stations. This mean relative difference is negative at ten stations, suggesting a small negative bias in the ACE-FTS partial columns over the altitude regions compared. Excellent correlation ( R =0.964) is observed between the ACE-FTS and FTIR partial columns, with a slope of 1.01 and an intercept of −0.20 on the line fitted to the data.
Atmospheric Chemistry and Physics. 01/2008;
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Strong K,
M. A. Wolff,
T. E. Kerzenmacher,
K. A. Walker,
P. F. Bernath,
Blumenstock T,
Boone C,
Catoire V,
Coffey M,
M. De Mazière, [......],
Semeniuk K,
Senten C,
G. P. Stiller, Strandberg A,
Taylor J,
Tétard C,
Toohey M,
Urban J,
Warneke T,
Wood S
[show abstract]
[hide abstract]
ABSTRACT: The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar occultation technique. One of these instruments, the ACE Fourier Transform Spectrometer (ACE-FTS), is measuring volume mixing ratio (VMR) profiles of nitrous oxide (N<sub>2</sub>O) from the upper troposphere to the lower mesosphere at a vertical resolution of about 3–4 km. In this study, the quality of the ACE-FTS version 2.2 N<sub>2</sub>O data is assessed through comparisons with coincident measurements made by other satellite, balloon-borne, aircraft, and ground-based instruments. These consist of vertical profile comparisons with the SMR, MLS, and MIPAS satellite instruments, multiple aircraft flights of ASUR, and single balloon flights of SPIRALE and FIRS-2, and partial column comparisons with a network of ground-based Fourier Transform InfraRed spectrometers (FTIRs). Overall, the quality of the ACE-FTS version 2.2 N<sub>2</sub>O VMR profiles is good over the entire altitude range from 5 to 60 km. Between 6 and 30 km, the mean absolute differences for the satellite comparisons lie between −42 ppbv and +17 ppbv, with most within ±20 ppbv. This corresponds to relative deviations from the mean that are within ±15%, except for comparisons with MIPAS near 30 km, for which they are as large as 22.5%. Between 18 and 30 km, the mean absolute differences are generally within ±10 ppbv, again excluding the aircraft and balloon comparisons. From 30 to 60 km, the mean absolute differences are within ±4 ppbv, and are mostly between −2 and +1 ppbv. Given the small N<sub>2</sub>O VMR in this region, the relative deviations from the mean are therefore large at these altitudes, with most suggesting a negative bias in the ACE-FTS data between 30 and 50 km. In the comparisons with the FTIRs, the mean relative differences between the ACE-FTS and FTIR partial columns are within ±6.6% for eleven of the twelve contributing stations. This mean relative difference is negative at ten stations, suggesting a small negative bias in the ACE-FTS partial columns over the altitude regions compared. Excellent correlation ( R =0.964) is observed between the ACE-FTS and FTIR partial columns, with a slope of 1.01 and an intercept of −0.20 on the line fitted to the data.
Atmospheric Chemistry and Physics Discussions. 01/2008;
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Dupuy E,
K. A. Walker,
Kar J,
C. D. Boone,
C. T. McElroy,
P. F. Bernath,
J. R. Drummond,
Skelton R,
S. D. McLeod,
R. C. Hughes, [......],
M. B. Tully,
Urban J,
Vanhellemont F,
T. von Clarmann,
P. von der Gathen,
C. von Savigny,
J. W. Waters,
J. C. Witte,
Wolff M,
J. M. Zawodny
[show abstract]
[hide abstract]
ABSTRACT: This paper presents extensive validation analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. The ACE satellite instruments operate in the mid-infrared and ultraviolet-visible-near-infrared spectral regions using the solar occultation technique. In order to continue the long-standing record of solar occultation measurements from space, a detailed quality assessment is required to evaluate the ACE data and validate their use for scientific purposes. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the mean differences range generally between 0 and +10% with a slight but systematic positive bias (typically +5%). At higher altitudes (45–60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments by up to ~40% (typically +20%). For the ACE-MAESTRO version 1.2 ozone data product, agreement within ±10% (generally better than ±5%) is found between 18 and 40 km for the sunrise and sunset measurements. At higher altitudes (45–55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (by as much as −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS and indicate a large positive bias (+10 to +30%) in this altitude range. In contrast, there is no significant difference in bias found for the ACE-FTS sunrise and sunset measurements. These systematic effects in the ozone profiles retrieved from the measurements of ACE-FTS and ACE-MAESTRO are being investigated. This work shows that the ACE instruments provide reliable, high quality measurements from the tropopause to the upper stratosphere and can be used with confidence in this vertical domain.
Atmospheric Chemistry and Physics Discussions. 01/2008;
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Clerbaux C,
George M,
Turquety S,
K. A. Walker,
Barret B,
Bernath P,
Boone C,
Borsdorff T,
J.-P. Cammas,
Catoire V, [......],
Robert C,
Schneider M,
Senten C,
Stiller G, Strandberg A,
Strong K,
Sussmann R,
Thouret V,
Urban J,
Wiacek A
[show abstract]
[hide abstract]
ABSTRACT: The Atmospheric Chemistry Experiment (ACE) mission was launched in August 2003 to sound the atmosphere by solar occultation. Carbon monoxide (CO), a good tracer of pollution plumes and atmospheric dynamics, is one of the key species provided by the primary instrument, the ACE-Fourier Transform Spectrometer (ACE-FTS). This instrument performs measurements in both the CO 1-0 and 2-0 ro-vibrational bands, from which vertically resolved CO concentration profiles are retrieved, from the mid-troposphere to the thermosphere. This paper presents an updated description of the ACE-FTS version 2.2 CO data product, along with a comprehensive validation of these profiles using available observations (February 2004 to December 2006). We have compared the CO partial columns with ground-based measurements using Fourier transform infrared spectroscopy and millimeter wave radiometry, and the volume mixing ratio profiles with airborne (both high-altitude balloon flight and airplane) observations. CO satellite observations provided by nadir-looking instruments (MOPITT and TES) as well as limb-viewing remote sensors (MIPAS, SMR and MLS) were also compared with the ACE-FTS CO products. We show that the ACE-FTS measurements provide CO profiles with small retrieval errors (better than 5% from the upper troposphere to 40 km, and better than 10% above). These observations agree well with the correlative measurements, considering the rather loose coincidence criteria in some cases. Based on the validation exercise we assess the following uncertainties to the ACE-FTS measurement data: better than 15% in the upper troposphere (8–12 km), than 30% in the lower stratosphere (12–30 km), and than 25% from 30 to 100 km.
Atmospheric Chemistry and Physics. 01/2008;
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Vigouroux C,
M. De Mazière,
Demoulin P,
Servais C,
Hase F,
Blumenstock T,
Kramer I,
Schneider M,
Mellqvist J, Strandberg A,
Velazco V,
Notholt J,
Sussmann R,
Stremme W,
Rockmann A,
Gardiner T,
Coleman M,
Woods P
[show abstract]
[hide abstract]
ABSTRACT: Within the European project UFTIR (Time series of Upper Free Troposphere observations from an European ground-based FTIR network), six ground-based stations in Western Europe, from 79° N to 28° N, all equipped with Fourier Transform infrared (FTIR) instruments and part of the Network for the Detection of Atmospheric Composition Change (NDACC), have joined their efforts to evaluate the trends of several direct and indirect greenhouse gases over the period 1995–2004. The retrievals of CO, CH4, C2H6, N2O, CHClF2, and O3 have been optimized. Using the optimal estimation method, some vertical information can be obtained in addition to total column amounts. A bootstrap resampling method has been implemented to determine annual partial and total column trends for the target gases. The present work focuses on the ozone results. The retrieved time series of partial and total ozone columns are validated with ground-based correlative data (Brewer, Dobson, UV-Vis, ozonesondes, and Lidar). The observed total column ozone trends are in agreement with previous studies: 1) no total column ozone trend is seen at the lowest latitude station Izaña (28° N); 2) slightly positive total column trends are seen at the two mid-latitude stations Zugspitze and Jungfraujoch (47° N), only one of them being significant; 3) the highest latitude stations Harestua (60° N), Kiruna (68° N) and Ny-Ålesund (79° N) show significant positive total column trends. Following the vertical information contained in the ozone FTIR retrievals, we provide partial columns trends for the layers: ground-10 km, 10–18 km, 18–27 km, and 27–42 km, which helps to distinguish the contributions from dynamical and chemical changes on the total column ozone trends. We obtain no statistically significant trends in the ground-10 km layer for five out of the six ground-based stations. We find significant positive trends for the lowermost stratosphere at the two mid-latitude stations, and at Ny-Ålesund. We find smaller, but significant trends for the 18–27 km layer at Kiruna, Harestua, Jungfraujoch, and Izaña. The results for the upper layer are quite contrasted: we find significant positive trends at Kiruna, Harestua, and Jungfraujoch, and significant negative trends at Zugspitze and Izaña. These ozone partial columns trends are discussed and compared with previous studies.
Atmospheric Chemistry and Physics. 01/2008;
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Gardiner T,
Forbes A,
M. De Mazière,
Vigouroux C,
Mahieu E,
Demoulin P,
Velazco V,
Notholt J,
Blumenstock T,
Hase F,
Kramer I,
Sussmann R,
Stremme W,
Mellqvist J, Strandberg A,
Ellingsen K,
Gauss M
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models.
Atmospheric Chemistry and Physics. 01/2008;
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Höpfner M,
T. von Clarmann,
Fischer H,
Funke B,
Glatthor N,
Grabowski U,
Kellmann S,
Kiefer M,
Linden A,
Milz M, [......],
Reddmann T,
Ruhnke R,
Schneider M, Strandberg A,
Toon G,
K. A. Walker,
Warneke T,
Wetzel G,
Wood S,
Zander R
[show abstract]
[hide abstract]
ABSTRACT: Altitude profiles of ClONO<sub>2</sub> retrieved with the IMK (Institut für Meteorologie und Klimaforschung) science-oriented data processor from MIPAS/Envisat (Michelson Interferometer for Passive Atmospheric Sounding on Envisat) mid-infrared limb emission measurements between July 2002 and March 2004 have been validated by comparison with balloon-borne (Mark IV, FIRS2, MIPAS-B), airborne (MIPAS-STR), ground-based (Spitsbergen, Thule, Kiruna, Harestua, Jungfraujoch, Izaña, Wollongong, Lauder), and spaceborne (ACE-FTS) observations. With few exceptions we found very good agreement between these instruments and MIPAS with no evidence for any bias in most cases and altitude regions. For balloon-borne measurements typical absolute mean differences are below 0.05 ppbv over the whole altitude range from 10 to 39 km. In case of ACE-FTS observations mean differences are below 0.03 ppbv for observations below 26 km. Above this altitude the comparison with ACE-FTS is affected by the photochemically induced diurnal variation of ClONO<sub>2</sub>. Correction for this by use of a chemical transport model led to an overcompensation of the photochemical effect by up to 0.1 ppbv at altitudes of 30–35 km in case of MIPAS-ACE-FTS comparisons while for the balloon-borne observations no such inconsistency has been detected. The comparison of MIPAS derived total column amounts with ground-based observations revealed no significant bias in the MIPAS data. Mean differences between MIPAS and FTIR column abundances are 0.11±0.12×10<sup>14</sup> cm<sup>−2</sup> (1.0±1.1%) and −0.09±0.19×10<sup>14</sup> cm<sup>−2</sup> (−0.8±1.7%), depending on the coincidence criterion applied. χ<sup>2</sup> tests have been performed to assess the combined precision estimates of MIPAS and the related instruments. When no exact coincidences were available as in case of MIPAS – FTIR or MIPAS – ACE-FTS comparisons it has been necessary to take into consideration a coincidence error term to account for χ<sup>2</sup> deviations. From the resulting χ<sup>2</sup> profiles there is no evidence for a systematic over/underestimation of the MIPAS random error analysis.
Atmospheric Chemistry and Physics. 01/2007;
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Gardiner T,
Forbes A,
Woods P,
deMaziere M,
Vigouroux C,
Mahieu E,
Demoulin P,
Velazco V,
Notholt J,
Blumenstock T,
Hase F,
Kramer I,
Sussman R,
Stremme W,
Mellqvist J, Strandberg A,
Ellingsen K,
Gauss M
[show abstract]
[hide abstract]
ABSTRACT: This paper describes the statistical analysis of annual trends in long term datasets of greenhouse gas measurements taken over ten or more years. The analysis technique employs a bootstrap resampling method to determine both the long-term and intra-annual variability of the datasets, together with the uncertainties on the trend values. The method has been applied to data from a European network of ground-based solar FTIR instruments to determine the trends in the tropospheric, stratospheric and total columns of ozone, nitrous oxide, carbon monoxide, methane, ethane and HCFC-22. The suitability of the method has been demonstrated through statistical validation of the technique, and comparison with ground-based in-situ measurements and 3-D atmospheric models.
Atmospheric Chemistry and Physics Discussions. 01/2007;
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Dils B,
M. De Mazière,
J. F. Müller,
Blumenstock T,
Buchwitz M,
R. de Beek,
Demoulin P,
Duchatelet P,
Fast H,
Frankenberg C, [......],
Stremme W,
Strong K,
Sussmann R,
Taylor J,
M. van den Broek,
Velazco V,
Wagner T,
Warneke T,
Wiacek A,
Wood S
[show abstract]
[hide abstract]
ABSTRACT: Total column amounts of CO, CH<sub>4</sub>, CO<sub>2</sub> and N<sub>2</sub>O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based quasi-global network of Fourier-transform infrared (FTIR) spectrometers. The SCIAMACHY data considered here have been produced by three different retrieval algorithms, WFM-DOAS (version 0.5 for CO and CH<sub>4</sub> and version 0.4 for CO<sub>2</sub> and N<sub>2</sub>O), IMAP-DOAS (version 1.1 and 0.9 (for CO)) and IMLM (version 6.3) and cover the January to December 2003 time period. Comparisons have been made for individual data, as well as for monthly averages. To maximize the number of reliable coincidences that satisfy the temporal and spatial collocation criteria, the SCIAMACHY data have been compared with a temporal 3rd order polynomial interpolation of the ground-based data. Particular attention has been given to the question whether SCIAMACHY observes correctly the seasonal and latitudinal variability of the target species. The present results indicate that the individual SCIAMACHY data obtained with the actual versions of the algorithms have been significantly improved, but that the quality requirements, for estimating emissions on regional scales, are not yet met. Nevertheless, possible directions for further algorithm upgrades have been identified which should result in more reliable data products in a near future.
Atmospheric Chemistry and Physics. 01/2006;
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Hak C,
Pundt I,
Trick S,
Kern C,
Platt U,
Dommen J,
Ordóñez C,
A. S. H. Prévôt,
Junkermann W,
Astorga-Lloréns C,
B. R. Larsen,
Mellqvist J, Strandberg A,
Yu Y,
Galle B,
Kleffmann J,
J. C. Lörzer,
G. O. Braathen,
Volkamer R
[show abstract]
[hide abstract]
ABSTRACT: Results from an intercomparison of several currently used in-situ techniques for the measurement of atmospheric formaldehyde (CH<sub>2</sub>O) are presented. The measurements were carried out at Bresso, an urban site in the periphery of Milan (Italy) as part of the FORMAT-I field campaign. Eight instruments were employed by six independent research groups using four different techniques: Differential Optical Absorption Spectroscopy (DOAS), Fourier Transform Infra Red (FTIR) interferometry, the fluorimetric Hantzsch reaction technique (five instruments) and a chromatographic technique employing C18-DNPH-cartridges (2,4-dinitrophenylhydrazine). White type multi-reflection systems were employed for the optical techniques in order to avoid spatial CH<sub>2</sub>O gradients and ensure the sampling of nearly the same air mass by all instruments. Between 23 and 31 July 2002, up to 13 ppbv of CH<sub>2</sub>O were observed. The concentrations lay well above the detection limits of all instruments. The formaldehyde concentrations determined with DOAS, FTIR and the Hantzsch instruments were found to agree within ±11%, with the exception of one Hantzsch instrument, which gave systematically higher values. The two hour integrated samples by DNPH yielded up to 25% lower concentrations than the data of the continuously measuring instruments averaged over the same time period. The consistency between the DOAS and the Hantzsch method was better than during previous intercomparisons in ambient air with slopes of the regression line not significantly differing from one. The differences between the individual Hantzsch instruments could be attributed in part to the calibration standards used. Possible systematic errors of the methods are discussed.
Atmospheric Chemistry and Physics. 01/2005;
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L. N. Yurganov,
Duchatelet P,
A. V. Dzhola,
D. P. Edwards,
Hase F,
Kramer I,
Mahieu E,
Mellqvist J,
Notholt J,
P. C. Novelli,
Rockmann A,
H. E. Scheel,
Schneider M,
Schulz A, Strandberg A,
Sussmann R,
Tanimoto H,
Velazco V,
J. R. Drummond,
J. C. Gille
[show abstract]
[hide abstract]
ABSTRACT: Carbon monoxide total column amounts in the atmosphere have been measured in the High Northern Hemisphere (30°–90° N, HNH) between January 2002 and December 2003, based on the analysis of infrared solar spectra recorded with spectrometers of high and moderate resolution. They are compared to ground-level CO mixing ratios and to total column amounts measured from space by the Terra/MOPITT instrument. In comparison to the unperturbed 2000–2001 period, all these databases reveal increased CO abundances in 2002–2003 summer-autumn times, with maximum anomalies observed in September 2002 and August 2003. Using a simple two-box model, the corresponding annual CO emission anomalies have been found equal to 98 Tg in 2002 and 142 Tg in 2003, thus close to those for 1996 and 1998. It is most likely that strong boreal forest fires in the HNH induced the increased CO burdens.
Atmospheric Chemistry and Physics Discussions. 01/2004;
