A comparison of satellite‐derived and aircraft‐measured regional surface sensible heat fluxes over the Beaufort Sea

Abstract

Motivated by the importance of quantifying the regional surface heat balance 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 resolution (AVHRR) IR satellite imagery. Their technique is based upon the determination of the pixel‐by‐pixel sea ice surface temperature from which estimates of sensible heat fluxes are then made. We compare the sensible heat fluxes over the Beaufort Sea computed using their methodology with those measured by a gust probe system on the National Oceanic and Atmospheric Administration P‐3 aircraft on April 18, 1992, during 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 large, 115 W m−2 for 1‐km average fluxes obtained from flight legs that included a 300‐m‐wide lead, but that regional values of sensible flux over 50–200 km of sea ice were small and positive, ∼8 W m−2. The sensible heat flux computed from the P‐3 showed that a value of CS = 1.1×10−3, where CS is the heat transfer coefficient relative to 10 m, is appropriate for the spring Beaufort Sea. We suggest that more realistic winds derived, for example, from the National Meteorological Center sea level pressure analyses be used instead of the constant value of 5 m s−1 now employed by Lindsay and Rothrock. We also found that the maximum value of ΔT, 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 factor of 1.9 when compared with direct measurements. Use of this ΔT correction factor, synoptic scale winds, and the calculated value of CS gave a good comparison between the AVHRR approach and aircraft fluxes measured over the region. The effective regional momentum drag coefficient CD relative to 10 m was 2.1×10−3, typical of Arctic pack ice.

Heat Budget in the Ice Cover of the Southern Okhotsk Sea Derived from In-situ Observations

“…However, the estimated value (40-60W/m2) is much smaller than that over lead in winter in the polar regions (e.g. 120W/m2 (Allison et al 1982), 130W/m2 (Ruffleux et al 1995), 189 W/m2 (Weller 1980), 115W/m2 (sensible heat flux; Walter et al 1995). This much smaller value is considered to be due to relatively higher air temperature than in the polar regions.…”

The Spring-Time Boundary Layer in the Central Arctic Observed during PAMARCMiP 2009

“…The (upward) heat fluxes above areas of thin ice compensate the downward heat fluxes above thick ice in a way that the sensible heat flux is around zero on a regional scale in winter [13]. Large heat fluxes for individual leads were observed in the lowest 30 m [54]. The vertical extent of plumes above leads depends on the thermal structure of the atmosphere, with stable stratifications prohibiting the development of large plumes above leads, and neutral stratification, e.g., after a front, allowing deeper plume penetration [22,47].…”

Turbulent heat fluxes over leads and polynyas, and their effects on arctic clouds during FIRE.ACE: Aircraft observations for April 1998

“…They used ice surface temperature derived from IR channels to estimate SHF. Walter et al (1995), using aircraft observations and National Oceanic and Atmospheric Administration (NOAA) AVHRR data, and applying a technique similar to the one given by Lindsay and Rothrock (1994), calculated SHF to be about 115 W m -2 over a 300-m wide lead and 2-17 W m -2 over a 200 × 200 km 2 region. They stressed that AVHRR fluxes were significantly smaller than those calculated from the aircraft observations.…”