COMPARISON OF DOAS RESULTS FROM THE AIRBORNE CARIBIC SYSTEM WITH SATELLITE OBSERVATIONS

摘要

Comparative studies between results from the CARIBICrnairborne DOAS instrument on board of CARIBIC andrnsatellite observations are presented. CARIBIC (CivilrnAircraft for the Regular Investigation of the atmospherernBased on an Instrument Container, www.caribic.de) observesrnphysical and chemical processes in the Earth’s atmospherernusing a fully automated measurement containerrnaboard a Lufthansa Airbus 340-600. A special inlet systemrnis mounted underneath the aeroplane with probes forrntrace gases, water vapour and aerosol particles. It alsornincludes three telescopes of a DOAS (Differential OpticalrnAbsorption Spectroscopy) system for remote sensing.rnEnhanced sulphur dioxide (SO_2) column densitiesrnwere observed by CARIBIC DOAS after the eruptionsrnof Kasatochi (Alaska, USA) and Eyjafjallaj?kull (Iceland)rnas well as downwind of the nickel smelter in Norilskrn(Siberia). For all cases detailed studies were performedrnand the data were used for comparisons withrnproducts from several satellite instruments. To reducernthe additional uncertainty caused by trajectory calculation,rnthe satellite with the shortest time difference relativernto the CARIBIC observation was validated. For thernKasatochi plume wind speeds were relevant for the comparisonrnin view of a discrepancy in the timing of aeroplanernand satellite overpass. In the case of a dedicatedrnflight designed to intercept parts of the Eyjafjallaj?kullrnplume, also Bromine Monoxide (BrO) was detected. Duernto high noise in both CARIBIC and GOME-2 (GlobalrnOzone Monitoring Experiment) data a qualitative comparisonrnof the BrO vertical column densities was not performed.rnFor Norilsk, where NO_2 enhancements were alsorndetected, wind data were used to estimate the SO_2 flux.rnThe flux estimate based on CARIBIC data was in a goodrnagreement with independent data including OMI (OzonernMonitoring Instrument) based results. In general, goodrnagreement between CARIBIC and the satellite data wasrnobtained.