SATELLITE-OBSERVATIONS OF A POLAR LOW OVER THE NORWEGIAN SEA BY SPECIAL SENSOR MICROWAVE IMAGER, GEOSAT, AND TIROS-N OPERATIONAL VERTICAL SOUNDER

Many polar lows are generated at the boundary between sea ice and the ocean, in regions of large temperature gradients, where in situ observ ations are rare or nonexistent. Since satellite observations are frequ ent in high-latitude regions, they can be used to detect polar lows an d track their propagation and evolution. The Special Sensor Microwave/ Imager (SSM/I) providing estimates of surface wind speed, integrated c loud liquid water content, water vapor content, and precipitation size ice-scattering signal over the ocean; the Geosat radar altimeter meas uring surface wind speed and significant wave height; and the TIROS-N Operational Vertical Sounder (TOVS) allowing the determination of temp erature and humidity profiles in the atmosphere have been used in syne rgy for a specific case which occurred in the Norwegian Sea on January , 23-24 1988. All three instruments show sharp atmospheric gradients a ssociated with the propagation of this low across the ocean, which per mit the detection of the polar low at a very early stage and tracking it during its development, propagation, and decay. The wind speed grad ients are measured with good qualitative agreement between the altimet er and SSM/I. TOVS retrieved fields prior to the formation of the low confirm the presence of an upper level trough, while during the mature phase baroclinicty can be observed in the 1000-500 hPa geopotential t hicknesses. Comparisons between satellite-retrieved products and analy ses of the operational Norwegian limited area model (150- and 50- km m esh) highlight the importance of satellites for the monitoring of such mesoscale phenomena.