Using Spaceborne Synthetic Aperture Radar to Improve Marine Surface Analyses

Abstract

The ever-changing weather and lack of in situ data in the Bering Sea warrants experimentation with new meteorological observing systems for this region. Spaceborne synthetic aperture radar (SAR) is well suited for observing the sea surface footprints of marine meteorological phenomena because its radiation is sensitive to centimeter-scale sea surface roughness, regardless of the time of day or cloud conditions. The near-surface wind field generates this sea surface roughness. Therefore, the sea surface footprints of meteorological phenomena are often revealed by SAR imagery when the main modulator of sea surface roughness is the wind. These attributes, in addition to the relatively high resolution of SAR products, make this instrument an excellent candidate for filling the meteorological observing needs over the Bering Sea. This study demonstrates the potential usefulness of SAR for observing Bering Sea meteorology by focusing on its ability to image the sea surface footprints of polar mesoscale cyclones (PMCs). These storms can form unexpectedly and are threatening to maritime interests. In this demonstration, a veteran meteorologist at the Anchorage National Weather Service Forecast Office is asked to produce a surface reanalysis for three separate archived cases when SAR imaged a PMC but the original analysis, produced without the aid of SAR data, did not display it. The results show that in these three cases the inclusion of SAR data in the analysis procedure leads to large differences between the original surface analysis and the reanalysis. Of particular interest is that, in each case, the PMC is added into the reanalysis. It is argued that the reanalyses more accurately portray the near-surface meteorology for each case.