On the Inversion of Wind Scatterometer Incomplete Data Sets

Abstract

SUMMARY ERS-1/2windscatterometers(WSC)datasetsmaycon-taincellsinwhichtwo,insteadofthree,measurements areavailable. Thesedata sets are called incomplete. Operational inversion procedures discardsuch data sets and therefore no wind field is estimated. This is very lim-iting in semi-closed seas such as the Mediterranean Sea. In this paper wepropose a new inversion procedure capable to retrieving near surface windfields from incomplete data sets. This procedure is an enhancement of analgorithm already proposed and tested by the authors. A set of comprehen-siveexperiments arepresented anddiscussed. Itisshown thattheinversionprocedure gets to remarkable results even in presence of a large number ofdoublets. key words: scatterometer, sea wind, wind field reconstruction 1. Introduction Near surface sea wind field knowledge is fundamental. Forinstance, it is a key element to force circulation models [1],to track tropical cyclones [2] and to detect oil spills [3].In general, accurate wind field knowledge facilitates rou-tine climatological/meteorological forecasting, supports de-partments of environmental protectionto bestdealwith life-threatening weather situations and accidents due to humanactivities.Nowdays it is well established that high quality windfield measurements can be obtained by means of remotelysensed data. Although, some very recent innovative tech-niques,basedonpolarimetricradiometers[4]andSARmea-surements [5], have been proposed to estimate the near sur-face wind field, the fundamental technique relies on scat-terometer measurements. In fact, at present time, physicaland technological aspects suggest that wind field estimatedbymeansofscatterometermeasurementsaremuchmorere-liable [6]. In addition, scatterometers allow a global cover-age.Inthispaper,anenhancementofthenewinversionpro-cedure described in [7],[8], in order to take into account in-complete data sets, is presented. The ERS-1/2C-bandfan-beam VV-polarized scatterometers, also simply known aswind scatterometers (WSC), share the active measurementinstrument (AMI) unit with the Synthetic Aperture Radar