A near‐infrared optimized DOAS method for the fast global retrieval of atmospheric CH4, CO, CO2, H2O, and N2O total column amounts from SCIAMACHY Envisat‐1 nadir radiances

Abstract

A new method for the fast and accurate retrieval of atmospheric trace gas total column amounts from near‐infrared nadir radiances, to be measured by the scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) spectrometer on board the European Space Agency Envisat‐1 satellite, has been investigated. It can be characterized as a weighting function modified differential optical absorption spectroscopy approach (WFM‐DOAS). The reference spectra of the linear fit include the trace gas total column weighting functions, a weighting function for a temperature profile shift, and a low‐order polynomial. Systematic errors due to uncertainties in atmospheric and surface parameters which cannot be retrieved, such as the trace gas vertical profile shapes, pressure and temperature profiles, aerosols, and the surface reflectivity, are quantified. The total column precisions of all trace gases to be retrieved from the SCIAMACHY near‐infrared channels 7 (1940–2040 nm) and 8 (2265–2385 nm) have been estimated to be better than 1% for H2O, CO2, and CH4, and better than 10% for N2O and CO. The potential of SCIAMACHY to measure regional CO2 and CH4 emission fluxes has been investigated. Both are important greenhouse gases to be monitored and reduced according to the Kyoto Protocol of the U.N. Framework Convention on Climate Change.