MONITORING OF ATMOSPHERIC TRACE GASES OVER CHINA USING GOME AND SCIAMACHY DATA

To monitor the air quality over East Asia, we use the measurements of two nadir sounding satellite instruments: GOME on ERS-2 (launched in April 1995) and SCIAMACHY on ENVISAT (launched in June 2001). From the measured spectra, concentrations of important trace gases can be retrieved. In the first section, the observed NO2 columns for 2003 are used in a top-down estimate of the anthropogenic NOx emissions for that year. The emissions in the chemical transport model are adjusted in such a way that the calculated concentrations correspond best with the satellite observations. The new emission estimates show important differences when compared with the EDGAR 3.2 database. In the second section, the data series of GOME and SCIAMACHY are combined to do retrievals of formaldehyde (CH2O) from 1996 to 2006. CH2O is one of the most abundant hydrocarbons and plays a central role in tropospheric chemistry. Its short lifetime combined with the relatively constant methane concentrations in the troposphere, make CH2O a crucial indicator of biomass burning, isoprene oxidation and other non-methane volatile organic compound oxidation over China. CH2O columns over Asia seem to increase over the years, but validation by ground measurements is strongly needed. In the last section, the near-infrared and short-waveinfrared measurements of SCIAMACHY are used to retrieve carbon monoxide (CO), methane (CH4), and carbon dioxide (CO2), which are important atmospheric constituents affecting air quality and climate. The CO columns over China correlate well with anthropogenic activity; the high CO columns in South-China at the start of 2004 can be attributed mainly to fires. On average, CH4 concentrations are highest south of Wuhan and around Chengdu and Chongqing; emissions peak in summer due to rice paddies. A seasonal cycle in CO2 is found which results from the regular release and uptake of CO2 by decaying and growing vegetation: maximum CO2 occurs around April-June, minimum around July-September. 1. TOP-DOWN ESTIMATE OF