SCIAMACHY LIMB NO_2 PROFILE VALIDATION

摘要

First validation results for stratospheric NO_2 profiles retrievedrnfrom SCIAMACHY limb scattering observationsrnare presented. The official operational offline (OL) processorrnNO_2 profile data product (version 2.1 as providedrnby DLR in April 2004) was compared to HALOE versionrn19 solar occultation measurements. Furthermore,rntwo scientific SCIAMACHY NO_2 profile data productsrn– developed at the Smithsonian Astrophysical Observatoryrn(SAO) in Cambridge, U.S.A., and at the Institute ofrnEnvironmental Physics (IUP/IFE) at Bremen, Germany –rnwere compared with LPMA-DOAS and SAOZ balloonrnand HALOE (version 19) and SAGE II (version 6.20)rnsatellite occultation measurements. The validation resultsrnpresented here are of preliminary nature due to thernknown Envisat pointing inaccuracies translating to SCIAMACHYrnlimb tangent height errors of up to 3 km. Thernoperational OL2.1 NO_2 concentrations are found to bernsystematically higher by about 50 % than photochemicallyrncorrected HALOE measurements for the 25 to 40rnkm altitude. Both scientific data products are generallyrnin good agreement with the balloon validation measurementsrn– within about 15 - 20% or within the error barsrnof the profiles – although in some cases significant differencesrnof up to 50 % between the SAO and the IUP/IFErnretrievals exist. The IUP/IFE scientific product agreesrnto within 15 % with photochemically corrected HALOErnmeasurements between 22 and 33 km altitude. Moreover,rnthe IUP/IFE scientific NO_2 concentrations are about 10rn- 35 % higher than photochemically corrected SAGE IIrnNO_2 concentrations within the 20 - 28 km altitude range.