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See detailGround-based remote sensing of tropospheric water vapour isotopologues within the project MUSICA
Schneider, M.; Barthlott, S.; Hase, F. et al

in Atmospheric Measurement Techniques (2012), 5(2012), 3007-3027

Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ... [more ▼]

Within the project MUSICA (MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water), long-term tropospheric water vapour isotopologue data records are provided for ten globally distributed ground-based mid-infrared remote sensing stations of the NDACC (Network for the Detection of Atmospheric Composition Change). We present a new method allowing for an extensive and straightforward characterisation of the complex nature of such isotopologue remote sensing datasets. We demonstrate that the MUSICA humidity profiles are representative for most of the troposphere with a vertical resolution ranging from about 2 km (in the lower troposphere) to 8 km (in the upper troposphere) and with an estimated precision of better than 10%. We find that the sensitivity with respect to the isotopologue composition is limited to the lower and middle troposphere, whereby we estimate a precision of about 30‰ for the ratio between the two isotopologues HD16O and H216O. The measurement noise, the applied atmospheric temperature profiles, the uncertainty in the spectral baseline, and the cross-dependence on humidity are the leading error sources. We introduce an a posteriori correction method of the cross-dependence on humidity, and we recommend applying it to isotopologue ratio remote sensing datasets in general. In addition, we present mid-infrared CO2 retrievals and use them for demonstrating the MUSICA network-wide data consistency. In order to indicate the potential of long-term isotopologue remote sensing data if provided with a well-documented quality, we present a climatology and compare it to simulations of an isotope incorporated AGCM (Atmospheric General Circulation Model). We identify differences in the multi-year mean and seasonal cycles that significantly exceed the estimated errors, thereby indicating deficits in the modeled atmospheric water cycle. [less ▲]

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See detailValidation of IASI FORLI carbon monoxide retrievals using FTIR data from NDACC
Kerzenmacher, T; Dils, B; Kumps, N et al

in Atmospheric Measurement Techniques (2012), 5

Carbon monoxide (CO) is retrieved daily and globally from space-borne IASI radiance spectra using the Fast Optimal Retrievals on Layers for IASI (FORLI) software developed at the Université Libre de ... [more ▼]

Carbon monoxide (CO) is retrieved daily and globally from space-borne IASI radiance spectra using the Fast Optimal Retrievals on Layers for IASI (FORLI) software developed at the Université Libre de Bruxelles (ULB). The IASI CO total column product for 2008 from the most recent FORLI retrieval version (20100815) is evaluated using correlative CO profile products retrieved from groundbased solar absorption Fourier transform infrared (FTIR) observations at the following FTIR spectrometer sites from the Network for the Detection of Atmospheric Composition Change (NDACC): Ny-Alesund, Kiruna, Bremen, Jungfraujoch, Izana and Wollongong. In order to have good statistics for the comparisons, we included all IASI data from the same day, within a 100 km radius around the ground-based stations. The individual ground-based data were adjusted to the lowest altitude of the co-located IASI CO profiles. To account for the different vertical resolutions and sensitivities of the ground-based and satellite measurements, the averaging kernels associated with the various retrieved products have been used to properly smooth coincident data products. It has been found that the IASI CO total column products compare well on average with the co-located ground-based FTIR total columns at the selected NDACC sites and that there is no significant bias for the mean values at all stations. [less ▲]

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See detailObserved and simulated time evolution of HCl, ClONO2, and HF total column abundances
Kohlhepp, R; Ruhnke, R; Chipperfield, M P et al

in Atmospheric Chemistry and Physics (2012), 12(7), 3527--3556

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra ... [more ▼]

Time series of total column abundances of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen fluoride (HF) were determined from ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites belonging to the Network for the Detection of Atmospheric Composition Change (NDACC) and located between 80.05°N and 77.82°S. By providing such a near-global overview on ground-based measurements of the two major stratospheric chlorine reservoir species, HCl and ClONO2, the present study is able to confirm the decrease of the atmospheric inorganic chlorine abundance during the last few years. This decrease is expected following the 1987 Montreal Protocol and its amendments and adjustments, where restrictions and a subsequent phase-out of the prominent anthropogenic chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to enable a stabilisation and recovery of the stratospheric ozone layer. The atmospheric fluorine content is expected to be influenced by the Montreal Protocol, too, because most of the banned anthropogenic gases also represent important fluorine sources. But many of the substitutes to the banned gases also contain fluorine so that the HF total column abundance is expected to have continued to increase during the last few years. The measurements are compared with calculations from five different models: the two-dimensional Bremen model, the two chemistry-transport models KASIMA and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby, the ability of the models to reproduce the absolute total column amounts, the seasonal cycles, and the temporal evolution found in the FTIR measurements is investigated and inter-compared. This is especially interesting because the models have different architectures. The overall agreement between the measurements and models for the total column abundances and the seasonal cycles is good. Linear trends of HCl, ClONO2, and HF are calculated from both measurement and model time series data, with a focus on the time range 2000–2009. This period is chosen because from most of the measurement sites taking part in this study, data are available during these years. The precision of the trends is estimated with the bootstrap resampling method. The sensitivity of the trend results with respect to the fitting function, the time of year chosen and time series length is investigated, as well as a bias due to the irregular sampling of the measurements. The measurements and model results investigated here agree qualitatively on a decrease of the chlorine species by around 1%yr-1. The models simulate an increase of HF of around 1%yr-1. This also agrees well with most of the measurements, but some of the FTIR series in the Northern Hemisphere show a stabilisation or even a decrease in the last few years. In general, for all three gases, the measured trends vary more strongly with latitude and hemisphere than the modelled trends. Relative to the FTIR measurements, the models tend to underestimate the decreasing chlorine trends and to overestimate the fluorine increase in the Northern Hemisphere. At most sites, the models simulate a stronger decrease of ClONO2 than of HCl. In the FTIR measurements, this difference between the trends of HCl and ClONO2 depends strongly on latitude, especially in the Northern Hemisphere. [less ▲]

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See detailProcess-evaluation of tropospheric humidity simulated by general circulation models using water vapor isotopologues: 1. Comparison between models and observations
Risi, C; Noone, D; Worden, J et al

in Journal of Geophysical Research (2012), 117(D5), 05303

N2 - The goal of this study is to determine how H2O and HDO measurements in water vapor can be used to detect and diagnose biases in the representation of processes controlling tropospheric humidity in ... [more ▼]

N2 - The goal of this study is to determine how H2O and HDO measurements in water vapor can be used to detect and diagnose biases in the representation of processes controlling tropospheric humidity in atmospheric general circulation models (GCMs). We analyze a large number of isotopic data sets (four satellite, sixteen ground-based remote-sensing, five surface in situ and three aircraft data sets) that are sensitive to different altitudes throughout the free troposphere. Despite significant differences between data sets, we identify some observed HDO/H2O characteristics that are robust across data sets and that can be used to evaluate models. We evaluate the isotopic GCM LMDZ, accounting for the effects of spatiotemporal sampling and instrument sensitivity. We find that LMDZ reproduces the spatial patterns in the lower and mid troposphere remarkably well. However, it underestimates the amplitude of seasonal variations in isotopic composition at all levels in the subtropics and in midlatitudes, and this bias is consistent across all data sets. LMDZ also underestimates the observed meridional isotopic gradient and the contrast between dry and convective tropical regions compared to satellite data sets. Comparison with six other isotope-enabled GCMs from the SWING2 project shows that biases exhibited by LMDZ are common to all models. The SWING2 GCMs show a very large spread in isotopic behavior that is not obviously related to that of humidity, suggesting water vapor isotopic measurements could be used to expose model shortcomings. In a companion paper, the isotopic differences between models are interpreted in terms of biases in the representation of processes controlling humidity. [less ▲]

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See detailCO2 total column retrieval by mid-IR FT Spectroscopy
Buschmann, M; Dohe, S; Mahieu, Emmanuel ULg et al

in Geophysical Research Abstracts (2012), 14

Over the last decade ground-based remote sensing measurements of CO2 have been established as an important component in the global observing system for greenhouse gases. Since 2004 the Total Carbon Column ... [more ▼]

Over the last decade ground-based remote sensing measurements of CO2 have been established as an important component in the global observing system for greenhouse gases. Since 2004 the Total Carbon Column Observing Network (TCCON) sites have provided CO2 retrievals in the near-IR region. CO2 can also be retrieved in the mid-IR spectral region and it would be of great benefit to use these spectra to produce CO2-data of sufficient precision. With this, 20 years of additional observations obtained in the mid-IR at a suite of FT-IR sites of the Network Detection of Atmospheric Composition Change (NDACC) will be accessible. We investigated a series of different CO2 microwindows in the mid-IR spectral region and present results from the most promising candidates for a showcase FT-IR site (Ny Alesund). Limitations of the approach are outlined and the feasibility of a future Mid-IR CO2-product of sufficient precision is discussed. [less ▲]

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See detailCarbon monoxide (CO) and ethane (C2H6) trends from ground-based solar FTIR measurements at six European stations, comparison and sensitivity analysis with the EMEP model
Angelbratt, J.; Mellqvist, J.; Simpson, D. et al

in Atmospheric Chemistry and Physics (2011), 11(17), 9253--9269

Trends in the CO and C2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from ... [more ▼]

Trends in the CO and C2H6 partial columns ~0–15 km) have been estimated from four European ground-based solar FTIR (Fourier Transform InfraRed) stations for the 1996–2006 time period. The CO trends from the four stations Jungfraujoch, Zugspitze, Harestua and Kiruna have been estimated to −0.45 ± 0.16% yr−1, −1.00 ± 0.24% yr−1, −0.62 ± 0.19 % yr−1 and −0.61 ± 0.16% yr−1, respectively. The corresponding trends for C2H6 are −1.51 ± 0.23% yr−1, −2.11 ± 0.30% yr−1, −1.09 ± 0.25% yr−1 and −1.14 ± 0.18% yr−1. All trends are presented with their 2-σ confidence intervals. To find possible reasons for the CO trends, the global-scale EMEP MSC-W chemical transport model has been used in a series of sensitivity scenarios. It is shown that the trends are consistent with the combination of a 20% decrease in the anthropogenic CO emissions seen in Europe and North America during the 1996–2006 period and a 20% increase in the anthropogenic CO emissions in East Asia, during the same time period. The possible impacts of CH4 and biogenic volatile organic compounds (BVOCs) are also considered. The European and global-scale EMEP models have been evaluated against the measured CO and C2H6 partial columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and Ny-Ålesund. The European model reproduces, on average the measurements at the different sites fairly well and within 10–22% deviation for CO and 14–31% deviation for C2H6. Their seasonal amplitude is captured within 6–35% and 9–124% for CO and C2H6, respectively. However, 61–98% of the CO and C2H6 partial columns in the European model are shown to arise from the boundary conditions, making the global-scale model a more suitable alternative when modeling these two species. In the evaluation of the global model the average partial columns for 2006 are shown to be within 1–9% and 37–50% of the measurements for CO and C2H6, respectively. The global model sensitivity for assumptions made in this paper is also analyzed. [less ▲]

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See detailValidation of five years (2003–2007) of SCIAMACHY CO total column measurements using ground-based spectrometer observations
de Laat, A. T. J.; Gloudemans, A. M. S.; Schrijver, H. et al

in Atmospheric Measurement Techniques (2010), 3(5), 1457--1471

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 ... [more ▼]

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. [less ▲]

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See detailValidation of version-4.61 methane and nitrous oxide observed by MIPAS
Payan, S.; Camy-Peyret, C.; Oelhaf, H. et al

in Atmospheric Chemistry and Physics (2009), 9(2), 413-442

The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In ... [more ▼]

The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign or ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH4 and N2O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61, full resolution MIPAS data covering the period 9 July 2002 to 26 March 2004) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. In the middle stratosphere, no significant bias is observed between MIPAS and correlative measurements, and MIPAS is providing a very consistent and global picture of the distribution of CH4 and N2O in this region. In average, the MIPAS CH4 values show a small positive bias in the lower stratosphere of about 5%. A similar situation is observed for N2O with a positive bias of 4%. In the lower stratosphere/upper troposphere (UT/LS) the individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH4 and N2O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH4 and N2O profiles are behaving as expected from the internal error estimation of IPF v4.61 and the estimated errors of the correlative measurements. [less ▲]

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See detailEvaluation of tropospheric and stratospheric ozone trends over Western Europe from ground-based FTIR network observations.
Vigouroux, C.; De Mazière, M.; Demoulin, Philippe ULg et al

in Atmospheric Chemistry and Physics (2008), 362(8), 6865-6886

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See detailPrecursor Gas Measurements (Chapter 2)
Notholt, J.; Bingemer, H.; Berresheim, H. et al

in Thomason, Larry W.; Peter, Thomas (Eds.) Assessment of Stratospheric Aerosol Properties (2006)

Assessments of stratospheric ozone have been conducted for nearly two decades and have evolved from describing ozone morphology to estimating ozone trends, and then to attribution of those trends ... [more ▼]

Assessments of stratospheric ozone have been conducted for nearly two decades and have evolved from describing ozone morphology to estimating ozone trends, and then to attribution of those trends. Stratospheric aerosol has only been integrated in assessments in the context of their effects on ozone chemistry and has not been critically evaluated itself. As a result, the Assessment of Stratospheric Aerosol Properties (ASAP) has been carried out by the WCRP project on Stratospheric Process and their Role in Climate (SPARC). The objective of this report is to present a systematic analysis of the state of knowledge of stratospheric aerosols including their precursors. It includes an examination of precursor concentrations and trends, measurements of stratospheric aerosol properties, trends in those properties, and modeling of aerosol formation, transport, and distribution in both background and volcanic conditions. The scope of this report is extensive; however, some aspects of stratospheric aerosol science have been deliberately excluded. For instance, we have not attempted to include an examination of polar stratospheric clouds (PSCs) or other clouds (such as cirrus clouds) occurring at or above the tropopause except in as much as they influence aerosol observations. Polar stratospheric clouds are the subject of a separate SPARC activity. We have produced a gap-free aerosol data base for use beyond this report. This required some new analysis that has not previously appeared in the technical literature. Similarly, the trend analysis required the development of a new analysis technique that is the subject of an article published in the Journal of Geophysical Research. New work is clearly identified in the present report. [less ▲]

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See detailInterannual variations of the carbon monoxide tropospheric burden between 30ºN and 90ºN in 1996-2003: ground-based and satellite measurements, estimate of biomass burning emissions
Yurganov, L. N.; Edwards, D. P.; Grechko, E. I. et al

in Geophysical Research Abstracts (2005), 7(EGU05-A-03850),

Carbon monoxide total column amounts in the atmosphere were measured in the High Northern Hemisphere (30º-90º N, HNH) between January 1996 and December 2003 using Fourier Transform Infrared high ... [more ▼]

Carbon monoxide total column amounts in the atmosphere were measured in the High Northern Hemisphere (30º-90º N, HNH) between January 1996 and December 2003 using Fourier Transform Infrared high resolution spectrometers installed at the NDSC (Network for Detection of Stratospheric Change) sites. A grating spectrometer of moderate resolution was employed for the same purpose at the Zvenigorod Research Station of the Institute of Atmospheric Physics near Moscow. CO mixing ratios were measured in the air samples obtained at the ground-level stations of the CMDL (Climate Modeling and Diagnostic Laboratory, NOAA) network. Total column CO amounts were measured from space by the Terra/MOPITT instrument between March, 2000, and December, 2003 (Edwards et al., 2004). Anomalies of monthly mean CO densities (related to a quiet period of 2000 - 2001) for different sites in the HNH were in agreement. This fact confirmed a good mixing of CO in the Northern Hemisphere on the montly basis that may be expected from a 1.5-2-month-long CO life-time. The data were integrated over the HNH reservoir (0-10 km in altitude and 30º-90º N in latitude) and the CO burden anomalies (in Tg) were analysed using a box model. Two CO sinks were taken into account: i) internal chemical removal in the reaction between CO and OH, and ii) transport of CO into the southertn part of the Northern hemisphere, where CO concentrations are usually lower. OH concentarations were taken from Spivakovsky et al. (2000). The air exchange through the 30º N boundary of the reservoir was estimated using the GEOS-CHEM model with a real meteorology of 1998 (Yurganov et al., 2004). The interannual variations of the sinks were neglected; a corresponding uncertainty in the retrieved source anomaly was estimated to be 20-30%. Since 1996 four years have been found to experience high CO emission of similar magnitude (1996, 1998, 2002, and 2003). During four years (1997, 1999, 2000, and 2001) the emissions were relatively low. Seasonal patterns of the emissions in active years were similar, maxima occured in July-August. However, in 2003 emissions in June-July were higher than in August. These semi-hemisphere averaged emission rates correlate with Siberian forest fire counts detected at night time by the ATSR radiometer of the ERS-2 satellite (R2 =0.51). The early peak of 2003 may be attributed to forest fires in Baikal region, Siberia. An inclusion of fire counts for other areas (Europe, North America) only worsen the correlation; this implies a decisive role of the Siberian fires for polluting the Northern Hemisphere troposphere (cf., Kasischke et al., 2005). It was estimated that the boreal forest fires during active years emit 30-60 Tg CO per month in July-August and 150-200 Tg annually. These emissions may be compared to industrial and transport pollution in the Northern Hemisphere estimated by Kasischke et al. (2005) as 290 Tg CO annually (i.e., 25 Tg monthly). [less ▲]

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See detailComparisons between SCIAMACHY Scientific Products and Ground-Based FTIR Data for Total Columns of CO, CH4 and N2O
De Mazière, M.; Barret, B.; Blumenstock, T. et al

Scientific conference (2004, May)

Total column amounts of CO, CH4 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based network of Fourier-transform infrared (FTIR ... [more ▼]

Total column amounts of CO, CH4 and N2O retrieved from SCIAMACHY nadir observations in its near-infrared channels have been compared to data from a ground-based network of Fourier-transform infrared (FTIR) spectrometers as well as to data obtained with an FTIR instrument during a ship cruise in January-February 2003, along the African West Coast. The SCIAMACHY data considered here have been produced by two different scientific retrieval algorithms, wfm-doas (version 4.0) and IMLM (version 5.1), and cover different time periods, making the number of reliable coincidences that satisfy the temporal and spatial collocation criteria rather limited and different for both. Also the quality of the SCIAMACHY Level 1 data, and thus of the Level 2 data for the different time periods is very different. Still the comparisons demonstrate the capability of SCIAMACHY, using one of both algorithms, to deliver geophysically valuable products for the target species under consideration, on a global scale. [less ▲]

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See detailGround-based FTIR measurements of O3- and climate-related gases in the free troposphere and lower stratosphere
De Mazière, M.; Barret, B.; Vigouroux, C. et al

in Zerefos, C. S. (Ed.) Proceedings Quadrennial Ozone Symposium (2004)

In the frame of the EC project UFTIR (Time series of Upper Free Troposphere observations from a European ground-based FTIR network), a common strategy for an optimal determination of the chemical ... [more ▼]

In the frame of the EC project UFTIR (Time series of Upper Free Troposphere observations from a European ground-based FTIR network), a common strategy for an optimal determination of the chemical composition in the free troposphere and lower stratosphere with ground-based Fourier-transform infrared (FTIR) spectrometers is being developed. The project focuses on 6 target species that are O3, CO, CH4, N2O, C2H6 and CHClF2 (HCFC-22). The strategy consists in selecting the most appropriate parameters to retrieve vertical concentration profiles from solar FTIR spectra. Among the important parameters are the spectral microwindows: they have been optimised to maximise the information content and to minimize the influence of poorly known spectroscopic data and interfering species. [less ▲]

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See detailVALIDATION OF ENVISAT-1 LEVEL-2 PRODUCTS RELATED TO LOWER ATMOSPHERE O3 AND NOy CHEMISTRY BY A FTIR QUASI-GLOBAL NETWORK
De Mazière, M.; Coosemans, T.; Barret, B. et al

Scientific conference (2002, December)

A coordinated action involving eleven stations of the ground-based Network for Detection of Stratospheric Change (NDSC) equipped with Fourier transform infrared (FTIR) instruments was conducted to ... [more ▼]

A coordinated action involving eleven stations of the ground-based Network for Detection of Stratospheric Change (NDSC) equipped with Fourier transform infrared (FTIR) instruments was conducted to contribute to the validation of the three atmospheric chemistry instruments onboard ENVISAT, that are MIPAS, SCIAMACHY and GOMOS. The target products for validation are total columns of O3, CH4, CO and some important NOy species (NO2, HNO3, NO) and the source gas N2O. Together the eleven stations cover the latitudes between 79 °N and 78°S, including polar, mid -latitude and subtropical and tropical locations. The goal is to contribute to the assessment of the data quality of the aforementioned ENVISAT instruments, from a quasi-global perspective. The period of intensive ground-based data collection for the benefit of the ENVISAT Validation Commissioning Phase that is dealt with in the present paper is July 15 to December 1, 2002. The FTIR network involved collected a data set corresponding to an equivalent of approximately 400 days of measurements; about three quarter of the data have already been submitted to the ENVISAT Calval database and are included in the present work. Unfortunately, the distribution of ENVISAT data has been slow and limited. Only a limited number of coincidences has been found for making data inter-comparisons. Therefore, the conclusions drawn in this paper are very preliminary and cover only a limited set of data products from SCIAMACHY only. Our findings up to now concerning the above mentioned target products are the following: (1) SCIAMACHY near infrared operational products (CO, CH4, N2O) have no scientific meaning yet, (2), the operational SCIAMACHY total vertical O3 column product derived in the ultraviolet window has undergone some improvements with changing versions of the processor(s) but it still underestimates the column by about 5 – 10 %, (3), the operational SCIAMACHY total vertical O3 column product derived in the visible window is unrealistically large, and (3), the operational NO2 total column product from SCIAMACHY seems to largely overestimate the real column, but very few coincidences and large dispersions of the data do inhibit any further conclusion at present. In a next phase, the same ground-based correlative data set will be exploited to further validate the ENVISAT data as soon as more and reprocessed data will be distributed. [less ▲]

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See detailGround-based infrared solar spectroscopic measurements of carbon monoxide during 1994 Measurement of Air Pollution From Space flights
Pougatchev, N. S.; Jones, N. B.; Connor, B. J. et al

in Journal Of Geophysical Research. Atmospheres (1998), 103(D15), 19317-19325

Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented ... [more ▼]

Results of the comparison of carbon monoxide ground-based infrared solar spectroscopic measurements with data obtained during 1994 Measurement of Air Pollution From Space (MAPS) flights are presented. Spectroscopic measurements were performed correlatively with April and October MAPS flights by nine research groups from Belgium, Canada, Germany, Japan, New Zealand, Russia, and the United States. Characterization of the techniques and error analysis were performed. The role of the CO a priori profile used in the retrieval was estimated. In most cases an agreement between spectroscopic and MAPS data is within estimated MAPS accuracy of +/-10%. [less ▲]

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