VALIDATION OF SCIAMACHY OPERATIONAL NEAR-REAL-TIME LEVEL-2 PRODUCTS BY FTIR AT THE GROUND TRUTHING STATION ZUGSPITZE

摘要

Solar FTIR measurements at the Permanent GroundrnTruthing Station Zugspitze (47 °N, 11 °E), Germany,rnare used to validate the SCIAMACHY operational NRTrnlevel-2 data products. The available SCIAMACHY datarnof the reprocessed Validation Reference Set of totalrncolumn O_3 (DOAS_0) and NO_2 (DOAS_1) arernaddressed, which was made available by ESA in earlyrn2004. Zugspitze FTIR column measurements arerncompared to SCIAMACHY columns of pixels within arngiven radius around the Zugspitze ground site. Ozonerncolumns agree well in absolute values and are able tornfollow the annual cycle in a realistic way comparable tornthe Zugspitze FTIR measurements. For operationalrnSCIAMACHY NO_2 retrievals, there seems to be arnsignificant overall underestimation of the real columnsrnon average. Furthermore, the operational NO_2 product isrnnot able to reflect the NO_2 decrease due to the annualrncycle during the second half of the year (2002). Fromrnanalysis of the zenith angle dependence of thernoperational SCIAMACHY columns and furtherrncomparison to the Scientific SCIAMACHY NO_2 datarnproduct (DOAS UB1.0) of the University of Bremen itrnis conjectured that there may be both a level-1 problemrnin the SCIAMACHY data, as well as a level-2 problemrnin the operational NO_2 retrievals, that both contribute tornthe failure of the operational NO_2 product in monitoringrnthe annual cycle.