Comparison of cloud properties at a coastal and inland site at the North Slope of Alaska

Multifilter rotating shadowband radiometers (MFRSRs) and microwave radiometers (MWRs) have been used to determine cloud optical depths, liquid water paths (LWPs), and effective cloud droplet radii at a coastal location (Barrow) and at a location approximately 100 km inland (Atqasuk), on Alaska's North Slope, for the period June through September, 1999. Some care is needed in processing the data to extract reliable information from these instruments, and extended periods of the Atqasuk MWR data in 2000 had to be discarded. An examination of the distributions of liquid water paths shows that the cloud properties were generally similar at the two sites but that there was a tendency for Barrow to have greater LWPs when the winds were from the south. Comparisons were made with predictions from the European Centre For Medium-Range Weather Forecasting model. The model tended to underpredict the moisture content of the clouds, particularly for winds from the north and east, but was generally consistent with the data in showing only small overall differences between Barrow and Atqasuk. In contrast, there were more significant differences in cloud properties only one grid point farther inland. Cloud optical depths were also estimated from the model and there was a tendency to underpredict this quantity as well. Additional simulations with a mesoscale model are being conducted to help identify the reasons for the directional dependence of cloud properties and their differences at the two sites.