A COMPARISON OF SATELLITE-DERIVED AND AIRCRAFT-MEASURED REGIONAL SURFACE SENSIBLE HEAT FLUXES OVER THE BEAUFORT SEA

Motivated by the importance of quantifying the regional surface heat b alance over Arctic sea ice in studying climate processes, Lindsay and Rothrock (1994) developed a methodology for computing regional surface sensible heat fluxes using readily available advanced very high resol ution (AVHRR) IR satellite imagery. Their technique is based upon the determination of the pixel-by-pixel sea ice surface temperature from w hich estimates of sensible heat fluxes are then made. We compare the s ensible heat fluxes over the Beaufort Sea computed using their methodo logy with those measured by a gust probe system on the National Oceani c and Atmospheric Administration P-3 aircraft on April 18, 1992, durin g the Leads Experiment. We use an AVHRR image recorded during the P-3 flight at 2303 UTC. We show that individual lead heat fluxes can be la rge, 115 W m(-2) for 1-km average fluxes obtained from flight legs tha t included a 300-m-wide lead, but that regional values of sensible flu x over 50-200 km of sea ice were small and positive, similar to 8 W m( -2). The sensible heat flux computed from the P-3 showed that a value of C-s = 1.1 x 10(-3), where C-s is the heat transfer coefficient rela tive to 10 m, is appropriate for the spring Beaufort Sea. We suggest t hat more realistic winds derived, for example, from the National Meteo rological Center sea level pressure analyses be used instead of the co nstant value of 5 m s(-1) now employed by Lindsay and Rothrock. We als o found that the maximum value of Delta T, the difference between air and surface temperature, used in the calculation of sensible heat flux using the Lindsay and Rothrock technique was underestimated by a fact or of 1.9 when compared with direct measurements. Use of this Delta T correction factor, synoptic scale winds, and the calculated value of C -s gave a good comparison between the AVHRR approach and aircraft flux es measured over the region. The effective regional momentum drag coef ficient C-D relative to 10 m was 2.1 x 10(-3) typical of Arctic pack i ce.