ARCTIC SEA-ICE SURFACE-TEMPERATURE FROM AVHRR

The surface temperature of arctic sea ice is estimated using the infra red channels of the Advanced Very High Resolution Radiometer (AVHRR) o n satellites NOAA-10 and NOAA-11. Temperature statistics are analyzed for 478 cells measuring 200 km square distributed over the entire Arct ic basin throughout 1989. The images are cloud masked manually, and th e surface temperature of the cloud-free area is estimated using an alg orithm specific to Arctic pack ice. The rms error of the estimate is t hought to be about 3.2 degrees C, largely due to uncertainty in cloud masking and the lack of knowledge of haze and ice crystal precipitatio n occurrence. The mean temperatures of the cells range from near 0 deg rees C in summer to below -45 degrees C in winter. Monthly averages ra nge down to -40 degrees C for the central Arctic and -29 degrees C for the peripheral seas. The monthly average standard deviation within ce lls in the central Arctic is highest in November (2.2 degrees C) and d rops to almost 0 degrees C in the summer. It is commonly twice as larg e in the peripheral seas as in the central Arctic. A computation of th e sensible heat flux at the surface is formulated based on the spatial variations of the surface temperature estimated with AVHRR. The contr ibution to the heat flux by the thin ice and leads that contribute to the spatial variability is found to be 8 W m(-2) larger in the central Arctic than found in earlier estimates.