Observation and Interpretation of Microwave Cloud Signatures over the Arctic Ocean during Winter

An analysis of satellite microwave brightness temperatures at 85 GHz (37 GHz) shows that these temperatures sometimes vary by more than 30 K (15 K) within 1 or 2 days at a single location over Arctic sea ice. This variation can be seen in horizontal brightness temperature distributions with spatial scales of hundreds of kilometers, as well as in brightness temperature time series observed at a single location. Analysis of satellite observations during winter shows that such brightness temperature warming frequently occurs in the Arctic Ocean, particularly in regions over which low pressure systems often pass. By comparing the observed microwave brightness temperature warming with ground-based measurements of geophysical variables collected during the Surface Heat Budget of the Arctic (SHEBA) experiment and with numerical prediction model analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF), it is found that brightness temperature anomalies are significantly correlated with clouds and precipitation. This finding raises the possibility of using satellite microwave data to estimate cloud liquid water path and precipitation in the Arctic. Factors contributing to the brightness temperature warming were examined, and it was found that the primary contributors to the observed warming were cloud liquid water and surface temperature change.