SCIAMACHY

Abstract: The Global Ozone Monitoring Experiment (GOME) is a new instrument aboard the European Space Agency’s (ESA) Second European Remote Sensing Satellite (ERS-2), which was launched in April 1995. The main scientific objective of the GOME mission is to determine the global distribution of ozone and several other trace gases, which play an important role in the ozone chemistry of the earth’s stratosphere and troposphere. GOME measures the sunlight scattered from the earth’s atmosphere and/or reflected by the surface in nadir viewing mode in the spectral region 240–790 nm at a moderate spectral resolution of between 0.2 and 0.4 nm. Using the maximum 960-km across-track swath width, the spatial resolution of a GOME ground pixel is 40 × 320 km2 for the majority of the orbit and global coverage is achieved in three days after 43 orbits. Operational data products of GOME as generated by DLR-DFD, the German Data Processing and Archiving Facility (D-PAF) for GOME, comprise absolute radiometrically calibrated e...

Abstract: Using the scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) pre-flight model satellite spectrometer, gas-phase absorption spectra of the most important atmospheric trace gases (O3, NO2, SO2, O2, OClO, H2CO, H2O, CO, CO2, CH4, and N2O) have been measured in the 230–2380 nm range at medium spectral resolution and at several temperatures between 203 and 293 K. The spectra show high signal-to-noise ratio (between 200 up to a few thousands), high baseline stability (better than 10−2) and an accurate wavelength calibration (better than 0.01 nm) and were scaled to absolute absorption cross-sections using previously published data. The results are important as reference data for atmospheric remote-sensing and physical chemistry. Amongst other results, the first measurements of the Wulf bands of O3 up to their origin above 1000 nm were made at five different temperatures between 203 and 293 K, the first UV-Vis absorption cross-sections of NO2 in gas-phase equilibrium at 203 K were recorded, and the ultraviolet absorption cross-sections of SO2 were measured at five different temperatures between 203 and 296 K. In addition, the molecular absorption spectra were used to improve the wavelength calibration of the SCIAMACHY spectrometer and to characterize the instrumental line shape (ILS) and straylight properties of the instrument. It is demonstrated that laboratory measurements of molecular trace gas absorption spectra prior to launch are important for satellite instrument characterization and to validate and improve the spectroscopic database.

Abstract: We have developed an improved solar reference spectrum for use in the analysis of atmospheric spectra from vacuum wavelengths of 200.07 through 1000.99 nm. The spectrum is developed by combining high spectral resolution ground-based and balloon-based solar measurements with lower spectral resolution but higher accuracy irradiance information. The new reference spectrum replaces our previous reference spectrum, and its derivatives, for use in a number of physical applications for analysis of atmospheric spectra, including: wavelength calibration; determination of instrument transfer (slit) functions; Ring effect (Raman scattering) correction; and correction for spectral undersampling of atmospheric spectra, particularly those that are dilute in absorbers. The applicability includes measurements from the GOME, SCIAMACHY, OMI, and OMPS satellite instruments as well as aircraft-, balloon-, and ground-based measurements.

Abstract: [1] A rapid increase of NO2 columns over China has been observed by satellite instruments in recent years. We present a 10-a regional trend of NOx emissions in China from 1995 to 2004 using a bottom-up methodology and compare the emission trends with the NO2 column trends observed from GOME and SCIAMACHY, the two spaceborne instruments. We use a dynamic methodology to reflect the dramatic change in China's NOx emissions caused by energy growth and technology renewal. We use a scenario analysis approach to identify the possible sources of uncertainties in the current bottom-up inventory, in comparison with the satellite observation data. Our best estimates for China's NOx emissions are 10.9 Tg in 1995 and 18.6 Tg in 2004, increasing by 70% during the period considered. NOx emissions and satellite-based NO2 columns show broad agreement in temporal evolution and spatial distribution. Both the emission inventory data and the satellite observations indicate a continuous and accelerating growth rate between 1996 and 2004 over east central China. However, the growth rate from the emission inventory is lower than that from the satellite observations. From 1996 to 2004, NOx emissions over the region increased by 61% according to the inventory, while a 95% increase in the NO2 columns measured by satellite was observed during the same period. We found good agreement during summertime but a large discrepancy during wintertime. The consistency between the summertime trends suggests that the bias cannot be due to systematic error of activity data or emission factors. The reasons for the discrepancy cannot yet be fully identified, but possible explanations include an underestimation in seasonal emission variations, variability of meteorology, NOx injection height, and the increasing trend of sulfate aerosols.