Abstract. The near-infrared nadir spectra measured by SCIAMACHY on-board ENVISAT contain information on the vertical columns of important atmospheric trace gases such as carbon monoxide (CO), methane (CH 4 ), and carbon dioxide (CO 2 ). The scientific algorithm WFM-DOAS has been used to retrieve this information. For CH 4 and CO 2 also column averaged mixing ratios (XCH 4 and XCO 2 ) have been determined by simultaneous measurements of the dry air mass. All available spectra of the year 2003 have been processed. We describe the algorithm versions used to generate the data (v0.4; for methane also v0.41) and show comparisons of monthly averaged data over land with global measurements (CO from MOPITT) and models (for CH 4 and CO 2 ). We show that elevated concentrations of CO resulting from biomass burning have been detected in reasonable agreement with MOPITT. The measured XCH 4 is enhanced over India, south-east Asia, and central Africa in September/October 2003 in line with model simulations, where they result from surface sources of methane such as rice fields and wetlands. The CO 2 measurements over the Northern Hemisphere show the lowest mixing ratios around July in qualitative agreement with model simulations indicating that the large scale pattern of CO 2 uptake by the growing vegetation can be detected with SCIAMACHY. We also identified potential problems such as a too low inter-hemispheric gradient for CO, a time dependent bias of the methane columns on the order of a few percent, and a few percent too high CO 2 over parts of the Sahara.

[1] Vertical profiles of carbon monoxide (CO) mixing ratio retrieved from MOPITT measurements have been analyzed. We find that variations in the vertical structure of CO can be detected in the MOPITT data. The Asian summer monsoon plume in CO is observed for the first time as a strong enhancement of CO in the upper troposphere (UT) over India and southern China indicating the effect of deep convective transport. Similarly, zonal mean height latitude cross-sections for the months of September -December, 2002 indicate deep convective transport of CO from biomass burning in the southern tropics. These findings show that MOPITT CO can provide valuable information on vertical transport phenomena in the troposphere.

Abstract. The three carbon gases carbon monoxide (CO), carbon dioxide (CO 2 ), and methane (CH 4 ) are important atmospheric constituents affecting air quality and climate. The near-infrared nadir spectra measured by SCIAMACHY on ENVISAT contain information on the vertical columns of these gases which we retrieve using a modified DOAS algorithm (WFM-DOAS or WFMD). Our main data products are CO vertical columns and dry-air column averaged mixing ratios of methane (CH 4 ) and CO 2 (denoted XCH 4 and XCO 2 ). For CO and CH 4 we present new results for the year 2003 obtained with an improved version of WFM-DOAS (WFMDv0.5) retrieved from Level 1 version 4 (Lv1v4) spectra. This data set has recently been compared with a network of ground based FTIR stations. Here we describe the WFMDv0.5 algorithm, present global and regional maps, and comparisons with global reference data. We show that major problems of the previous versions (v0.4 and v0.41) related to the varying ice-layer on the SCIAMACHY channel 8 detector have been solved. Compared to MOPITT the SCIAMACHY CO columns are on average higher by about 10-20%. Regionally, however, especially over central South America, differences can be much larger. For methane we present global and regional maps which are compared to TM5 model simulations performed using standard methane emission inventories. We show that methane source regions can be clearly detected with SCIAMACHY. We also show that the methane data product can be significantly further improved using Lv1v5 spectra with improved calibration. For CO 2 we present three years of SCIAMACHY CO 2 measurements over Park Falls, Wisconsin, USA, retrieved from Lv1v5. We show that the quality of CO 2 retrieved from Correspondence to: M. Buchwitz (michael.buchwitz@iup.physik.uni-bremen.de) these spectra is significantly higher compared to WFMDv0.4 XCO 2 retrieved from Lv1v4.

[1] Denitrification has been studied using measurements of stratospheric HNO 3 and N 2 O by the Airborne Submillimeter Radiometer (ASUR), operated on board the NASA DC-8 during SOLVE/THESEO 2000. Lidar measurements taken on board the same aircraft have been used to distinguish between temporary uptake of HNO 3 in polar stratospheric clouds (PSCs) and denitrification events. To derive an NO y budget, ClNO 3 data by balloonborne and ground-based Fourier transform infrared measurements and a model estimate of NO x + 2N 2 O 5 have been considered. The HNO 3 profiles of sporadic ASUR measurements without PSC coverage in January suggest that denitrification had started in the vortex core region by then. Vortexwide denitrification was found in midMarch 2000. Corrected for diabatic descent using the N 2 O measurements, a vortexaveraged NO y deficit between 1.2 ± 0.9 ppb at about 16 km altitude and 5.3 ± 2.7 ppb at about 20.5 km altitude was derived compared to December 1999, based on an observed decrease in HNO 3 between 2.2 and 3.5 ppb during this time period. A shift in the NO y partitioning from HNO 3 toward ClNO 3 of about 0.4 to 0.7 ppb was observed in midMarch compared to December, indicating that chlorine deactivation was occurring. Comparisons with the SLIMCAT three-dimensional chemical transport model applying denitrification schemes based on ice and nitric acid trihydrate particles in equilibrium, respectively, reveal agreement within the error bars at higher altitudes ($19 km) but show discrepancies at lower altitudes ($16 km). It is suggested that more sophisticated denitrification schemes are needed to generally describe denitrification processes.

[1] A detailed analysis of available in situ and remotely sensed N 2 O and CH 4 data measured in the 1999/2000 winter Arctic vortex has been performed in order to quantify the temporal evolution of vortex descent. Differences in potential temperature (q) among balloon and aircraft vertical profiles (an average of 19-23 K on a given N 2 O or CH 4 isopleth) indicated significant vortex inhomogeneity in late fall as compared with late winter profiles. A composite fall vortex profile was constructed for 26 November 1999, whose error bars encompassed the observed variability. High-latitude extravortex profiles measured in different years and seasons revealed substantial variability in N 2 O and CH 4 on q surfaces, but all were clearly distinguishable from the first vortex profiles measured in late fall 1999. From these extravortex-vortex differences we inferred descent prior to 26 November: as much as 397 ± 15 K (1s) at 30 ppbv N 2 O and 640 ppbv CH 4 , and falling to 28 ± 13 K above 200 ppbv N 2 O and 1280 ppbv CH 4 . Changes in q were determined on five N 2 O and CH 4 isopleths from 26 November through 12 March, and descent rates were calculated on each N 2 O isopleth for several time intervals. The maximum descent rates were seen between 26 November and 27 January: 0.82 ± 0.20 K/day averaged over 50-250 ppbv N 2 O. By late winter (26 February to 12 March), the average rate had decreased to 0.10 ± 0.25 K/day. Descent rates also decreased with increasing N 2 O; the winter average (26 November to 5 March) descent rate varied from 0.75 ± 0.10 K/day at 50 ppbv to 0.40 ± 0.11 K/day at 250 ppbv. Comparison of these results with observations and models of descent in prior years showed very good overall agreement. Two models of the 1999/2000 vortex descent, SLIMCAT and REPROBUS, despite q offsets with respect to observed profiles of up to 20 K on most tracer isopleths, produced descent rates that agreed very favorably with the inferred rates from observation. INDEX TERMS: 3334

Vertical profiles of ozone concentration in the high latitudes were observed by the Improved Limb Atmospheric Spectrometer (ILAS) aboard the Advanced Earth Observing Satellite (ADEOS) from November 1996 to June 1997. The ozone data obtained by the version 5.20 ILAS retrieval algorithm are compared with those obtained by the version 19 Halogen Occultation Experiment (HALOE), the version 6 Stratospheric Aerosol and Gas Experiment (SAGE) II, and the version 6 Polar Ozone and Aerosol Measurement (POAM) II retrieval algorithms. The ILAS data are also compared with ozone data measured by ozonesondes, instruments on board balloons or an aircraft, and ground‐based instruments. The ILAS ozone data generally agree with its correlative data between 11 and 64 km with some exceptions. Quantitatively, the median value of the relative difference (absolute difference divided by its mean value) for these comparisons was within ±10%. Relative differences (18%) exceeding the combined measurement errors were found around 45–55 km altitude from comparisons with the HALOE and SAGE II data in January 1997 in the Southern Hemisphere (SH). Larger relative differences (around 50%) were also found below 15 km from comparisons with the HALOE and POAM II data in November 1996 in the SH, but these absolute differences were 0.10–0.16 ppmv as the median value. The ozone data processed by the version 5.20 were improved compared to the former version 3.10, which is available to the general public. The version 5.20 ozone data can be used for scientific analysis purposes based on the accuracy of the data in comparison with these other instruments.

In the winter 1999/2000 the Airborne Submillimeter Radiometer (ASUR) participated in the Stratospheric Aerosol and Gas Experiment III Ozone Loss and Validation Experiment/Third European Stratospheric Experiment on Ozone project on board the NASA research aircraft DC‐8. During three deployments in early December 1999, late January, and early March 2000, the ASUR instrument took various measurements of ozone and key species related to stratospheric ozone chemistry. After the sunlight reached the vortex region in January 2000 peak values of about 1.8 ppb ClO were measured by ASUR. There was nearly no ozone destruction observed during the period between mid December 1999 and late January 2000. As expected from ASUR observation of high chlorine activation and continuously low temperatures until mid March, significant ozone depletion was observed between late January and mid March 2000. In order to determine ozone loss it is important to separate dynamical and chemical effects. Since N2O is a good tracer due to its chemical stability in the lower stratosphere for determining ozone changes due to descent of air, ozone loss can be estimated from simultaneous measurements of ozone and N2O by ASUR. Between mid December 1999 and mid March 2000 a chemical ozone loss of about 30% (eq 1.1 ppm) in the altitude range between 19.0 and 22.2 km and of about 40% (eq 1.15 ppm) between 16.0 and 18.1 km was observed. The air masses subsided 2.1–3.2 km in the lower stratosphere due to diabatic descent in the period from mid December 1999 to mid March 2000 as derived from ASUR N2O measurements. Vortex‐averaged ASUR measurements of ozone are systematical greater than results from the Global Ozone Monitoring Experiment (GOME) which has a similar vertical resolution than ASUR. This, however, has little impact on the determination of delta ozone and chemical loss estimates.

Vertical profiles of nitrous oxide and methane at high latitudes (57–72°N; 64–89°S) were observed by the Improved Limb Atmospheric Spectrometer (ILAS) solar occultation sensor aboard Advanced Earth Observing Satellite. These measurements were made continuously from November 1996 through June 1997 with some additional periods in September–October 1996. A validation study of the nitrous oxide and methane data processed with the Version 5.20 ILAS retrieval algorithm is presented in this paper. Comparisons are made with (1) nitrous oxide and methane obtained by the ILAS validation balloon campaigns at Kiruna, Sweden, and at Fairbanks, Alaska, in the Arctic; (2) nitrous oxide and methane by the Photochemistry of Ozone Loss in the Arctic Region in Summer aircraft campaign in the Arctic; (3) nitrous oxide by the ground‐based spectroscopic measurements and by the aircraft‐based remote sensing measurements in the Arctic; and (4) methane by satellite measurements of the Version 19 Halogen Occultation Experiment in the Arctic and Antarctic. Comparisons of ILAS nitrous oxide and methane with Upper Atmosphere Research Satellite Reference Atmosphere data are also made. The results of the comparisons and additional ILAS internal consistency analyses are as follows: (1) the uncertainty of ILAS nitrous oxide is better than 10% over 10–30 km in altitude, and is larger than 50% over 30–40 km, which is comparable to the expected total errors of the ILAS measurements; (2) the uncertainty of ILAS methane is better than 10% over 10–50 km, except for 15–30 km in winter with positive biases exceeding 20%, which is smaller than or comparable to the expected total errors of the ILAS measurements (the quality of ILAS methane in the polar lower stratosphere is better in summer than in winter). In summary, the characteristics of ILAS measurements, i.e., high sampling frequency in polar latitudes with high vertical resolution, along with the good quality of ILAS Version 5.20 nitrous oxide for 10–40 km and the good quality of ILAS Version 5.20 methane for 10–50 km except for 15–30 km in winter, make the ILAS nitrous oxide and methane data set valuable for scientific study of various polar stratospheric phenomena.