NOCTILUCENT CLOUD OBSERVATIONS AND PARTICLE SIZE RETRIEVAL FROM GOMOS / ENVISAT

摘要

GOMOS (Global Ozone Monitoring by Occultation ofrnStars), on board the European platform ENVISATrnlaunched in 2002, is a stellar occultation instrumentrncombining four spectrometers and two fast photometers.rnOn the day side, in addition to star light, GOMOSrnmeasures also the solar light scattered by thernatmospheric molecules. In the summer polar days, polarrnmesospheric clouds (PMC) are clearly detected usingrnthe photometers signals. The sun-synchronous orbit ofrnENVISAT allows observing these clouds in bothrnhemispheres. Their main properties (occurrencernfrequency, peak accuracy is possible thanks to thernstellar occultation technique. Moreover, the observationrnof these clouds with the spectrometers provides thernspectral dependence of the light scattered by the NLCrnparticles, from which it is possible to derive their radii,rnfor the northern hemisphere. These clouds at the edge ofrnspace have been studied using GOMOS data from 2002rnto 2010. More than 21 000 clouds were observed duringrnthis period. In this paper we present the data setrnobtained, focusing on the spectral analysis. The particlernsize retrieval algorithm is explained.