2002 ARCSS All-Hands Workshop

Surface Temperature of The Arctic: Comparison of TOVS Satellite Retrievals with Surface Observations

Yonghua Chen¹, Jennifer A. Francis², James R. Miller^3
1Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ, 08901, USA, chen@imcs.rutgers.edu
²USA, francis@imcs.rutgers.edu
³USA, miller@arctic.rutgers.edu

Surface temperature is a fundamental parameter for climate research. Over the Arctic Ocean and neighboring seas conventional temperature observations are often of uncertain quality, however, owing to logistical obstacles in making measurements over sea ice in harsh environmental conditions. Satellites offer an attractive alternative, but standard methods encounter difficulty in detecting clouds in the frequent surface-based temperature inversion and when solar radiation is absent. The TIROS Operational Vertical Sounder Polar Pathfinder (TOVS Path-P) data set provides nearly 20 years (1979-1997) of satellite-derived, gridded surface skin temperatures for the Arctic region north of 60 N. Another data set based on surface observations has also recently become available. The International Arctic Buoy Program/Polar Exchange at the Surface (IABP/POLES) project provides a gridded near-surface air temperature data set based on optimally interpolated observations from Russian drifting ice stations, buoys, and land stations from 1979-1997.

In this study, we compare these two data sets and find area with large differences (4 to 6 K) in both winter and summer. Over the ice-covered Arctic Ocean in both seasons TOVS temperatures are substantially colder than POLES and over the Greenland-Iceland-Norwegian (GIN) Sea TOVS is warmer. Using point measurements from manned ice stations and ships we find that POLES is too warm (~2K on average) in January. The bias is larger (~4K) in regions where the primary source of data is buoys, which contain warm biases in winter owing to the insulation effect of snow covering the sensors. The difference between skin and 2-meter temperatures accounts for approximately 1 K of the January discrepancy between POLES and TOVS. Over the GIN Sea in both seasons POLES is too cold (~7K) because values are based primarily on analyses from the National Centers for Environmental Prediction (NCEP). In July the TOVS temperatures are approximately 8K too cold over ice-covered regions owing to poor retrievals when cloud cover exceeds 95%. When overcast retrievals are removed, this difference is reduced to 2K. We therefore recommend that TOVS retrievals be rejected in summer when the retrieved cloud cover is over 95%.

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