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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 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 detailA new method to detect long term trends of methane (CH4) and nitrous oxide (N2O) total columns measured within the NDACC ground-based high resolution solar FTIR network
Angelbratt, J.; Mellqvist, J.; Blumenstock, T. et al

in Atmospheric Chemistry and Physics (2011), 11(13), 6167--6183

Total columns measured with the ground-based solar FTIR technique are highly variable in time due to atmospheric chemistry and dynamics in the atmosphere above the measurement station. In this paper, a ... [more ▼]

Total columns measured with the ground-based solar FTIR technique are highly variable in time due to atmospheric chemistry and dynamics in the atmosphere above the measurement station. In this paper, a multiple regression model with anomalies of air pressure, total columns of hydrogen fluoride (HF) and carbon monoxide (CO) and tropopause height are used to reduce the variability in the methane (CH4) and nitrous oxide (N2O) total columns to estimate reliable linear trends with as small uncertainties as possible. The method is developed at the Harestua station (60 N, 11 E, 600m a.s.l.) and used on three other European FTIR stations, i.e. Jungfraujoch (47 N, 8 E, 3600m a.s.l.), Zugspitze (47 N, 11 E, 3000m a.s.l.), and Kiruna (68 N, 20 E, 400m a.s.l.). Linear CH4 trends between 0.13±0.01-0.25±0.02%yr-1 were estimated for all stations in the 1996-2009 period. A piecewise model with three separate linear trends, connected at change points, was used to estimate the short term fluctuations in the CH4 total columns. This model shows a growth in 1996–1999 followed by a period of steady state until 2007. From 2007 until 2009 the atmospheric CH4 amount increases between 0.57±0.22–1.15±0.17%yr-1. Linear N2O trends between 0.19±0.01–0.40±0.02%yr-1 were estimated for all stations in the 1996-2007 period, here with the strongest trend at Harestua and Kiruna and the lowest at the Alp stations. From the N2O total columns crude tropospheric and stratospheric partial columns were derived, indicating that the observed difference in the N2O trends between the FTIR sites is of stratospheric origin. This agrees well with the N2O measurements by the SMR instrument onboard the Odin satellite showing the highest trends at Harestua, 0.98±0.28%yr-1, and considerably smaller trends at lower latitudes, 0.27±0.25%yr-1. The multiple regression model was compared with two other trend methods, the ordinary linear regression and a Bootstrap algorithm. The multiple regression model estimated CH4 and N2O trends that differed up to 31% compared to the other two methods and had uncertainties that were up to 300% lower. Since the multiple regression method were carefully validated this stresses the importance to account for variability in the total columns when estimating trend from solar FTIR data. [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 detailTechnical Note: Harmonized retrieval of column-integrated atmospheric water vapor from the FTIR network - First examples for long-term records and station trends
Sussmann, R.; Borsdorff, T.; Rettinger, M. et al

in Atmospheric Chemistry and Physics (2009), 9(22), 8987-8999

We present a method for harmonized retrieval of integrated water vapor (IWV) from existing, long-term, measurement records at the ground-based mid-infrared solar FTIR spectrometry stations of the Network ... [more ▼]

We present a method for harmonized retrieval of integrated water vapor (IWV) from existing, long-term, measurement records at the ground-based mid-infrared solar FTIR spectrometry stations of the Network for the Detection of Atmospheric Composition Change (NDACC). Correlation of IWV from FTIR with radiosondes shows an ideal slope of 1.00(3). This optimum matching is achieved via tuning one FTIR retrieval parameter, i.e., the strength of a Tikhonov regularization constraining the derivative (with respect to height) of retrieved water profiles given in per cent difference relative to an a priori profile. All other FTIR-sonde correlation parameters (intercept = 0.02(12) mm, bias = 0.02(5) mm, standard deviation of coincident IWV differences (stdv) = 0.27 mm, R = 0.99) are comparable to or better than results for all other ground-based IWV sounding techniques given in the literature. An FTIR-FTIR side-by-side intercomparison reveals a strong exponential increase in stdv as a function of increasing temporal mismatch starting at Δt ≈ 1 minute. This is due to atmospheric water vapor variability. Based on this result we derive an upper limit for the precision of the FTIR IWV retrieval for the smallest Δt (= 3.75 min) still giving a statistically sufficient sample (32 coincidences), i.e., precision (IWVFTIR) < 0.05 mm (or 2.2 % of the mean IWV). The bias of the IWV retrievals from the two different FTIR instruments is nearly negligible (0.02(1) mm). The optimized FTIR IWV retrieval is set up in the standard NDACC algorithm SFIT 2 without changes to the code. A concept for harmonized transfer of the retrieval between different stations deals with all relevant control parameters; it includes correction for differing spectral point spacings (via regularization strength), and final quality selection of the retrievals (excluding the highest residuals (measurement minus model), 5% of the total). As first application examples long-term IWV data sets are retrieved from the FTIR records of the Zugspitze (47.4 °N, 11.0 °E, 2964 m a.s.l.) and Jungfraujoch (46.5 °N, 8.0 °E, 3580 m a.s.l.) NDACC sites. Station-trend analysis comprises a linear fit after subtracting an intra-annual model (3 Fourier components) and constructing an uncertainty interval [95 % confidence] via bootstrap resampling. For the Zugspitze a significant trend of 0.79 [0.65, 0.92] mm/decade is found for the time interval [1996 - 2008], whereas for the Jungfraujoch no significant trend is found. This confirms recent findings that strong variations of IWV trends do occur above land on the local to regional scale (≈250 km) in spite of homogeneous surface temperature trends. This paper provides a basis for future exploitation of more than a dozen existing, multi-decadal FTIR measurement records around the globe for climate studies. [less ▲]

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See detailValidation of ozone measurements from the Atmospheric Chemistry Experiment (ACE)
Dupuy, Eric; Walker, K. A.; Kar, J. et al

in Atmospheric Chemistry and Physics (2009), 9(2), 287-343

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 ... [more ▼]

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 (similar to 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. [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 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 detailGeophysical Validation of SCIAMACHY NO2 Vertical Columns: Overview of Early 2004 Results
Lambert, Jean-Christopher; Blumenstock, Thomas; Boersma, F. et al

in Proceedings of the Second Workshop on the Atmospheric Chemistry Validation of ENVISAT (ACVE-2), ESA-ESRIN, Frascati, Italy, 3-7 May 2004 (ESA SP-562, August 2004) ESC01JL1 (2004, August)

Following the recommendations drawn after the Commissioning Phase of the ENVISAT satellite in 2002, SCIAMACHY near real time data processors were upgraded to version 5.01 in early 2004. Before public ... [more ▼]

Following the recommendations drawn after the Commissioning Phase of the ENVISAT satellite in 2002, SCIAMACHY near real time data processors were upgraded to version 5.01 in early 2004. Before public release of the new SCIAMACHY nitrogen dioxide (NO2) vertical column data product, several validation teams investigated its improvement and assessed its geophysical consistency by means of correlative studies involving NDSC-affiliated ground-based networks of DOAS UV-visible and FTIR spectrometers and the ERS-2 GOME satellite. In parallel, preliminary SCIAMACHY NO2 column data products generated by research processors under development at scientific institutes were also tested, using the same correlative data and validation procedures. Digesting the results obtained by a list of validation teams and SCIAMACHY data processing teams, this overview paper draws a preliminary quality assessment of the SCIAMACHY NO2 column data sets available in spring 2004. [less ▲]

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See detailFirst Ground-Based Validation of SCIAMACHY V5.01 Ozone Column
Lambert, Jean-Christopher; Allaart, M; Andersen, S.B. et al

in Proceedings of the Second Workshop on the Atmospheric Chemistry Validation of ENVISAT (ACVE-2), ESA-ESRIN, Frascati, Italy, 3-7 May 2004 (ESA SP-562, August 2004) ESC01JL1 (2004, August)

In early 2004, the near real-time data processor of ENVISAT SCIAMACHY (SCI_NL) was upgraded to version 5.01. Based on the correlative measurements acquired and collected during the commissioning phase of ... [more ▼]

In early 2004, the near real-time data processor of ENVISAT SCIAMACHY (SCI_NL) was upgraded to version 5.01. Based on the correlative measurements acquired and collected during the commissioning phase of the satellite in 2002, a preliminary validation was organised to verify the improvement and assess the geophysical consistency of the new SCIAMACHY ozone vertical column data product. The present overview summarises the results obtained by a list of validation teams and involving ground-based data acquired from pole to pole by complementary ground-based sensors. The studies conclude to an improvement compared to previous versions 3.5x. They also confirm the presence of expected errors (e.g. dependence on solar elevation and on ozone column) inherited from the GOME Data Processor GDP 2.4, on which the SCIAMACHY processor SCI_NL is based. [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, Martine; Coosemans, Thierry; Barret, Brice et al

in Proceedings of Envisat Validation Workshop, Frascati, Italy, December 9-13, 2002, ESA SP-531, 2003 (2003)

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, N 2O) 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 (4), 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 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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