Wind jets and wind waves off the Pacific coast of northern Japan under winter monsoon captured by combined use of scatterometer, synthetic aperture radar, and altimeter

Abstract

Wind jets and wind waves off the Pacific coast of northern Japan under the east Asian winter monsoon are investigated using scatterometer, synthetic aperture radar (SAR), and altimeters. First, we depict two prevailing wind flow patterns associated with the northwesterly winter monsoon. They are derived by averaging QuikSCAT wind vectors when the 850‐hPa pressure level wind directions are within 260°–290° and 290°–330°, respectively. Wind jets and wakes are formed in different regions depending on the approach angle of wind to the topographic features. Second, using high‐resolution satellite observations of QuikSCAT and ERS‐2 SAR for wind, and TOPEX/Poseidon and ERS‐2 radar altimeter for significant wave height, we present two case studies corresponding to the two prevailing wind flow patterns in order to investigate wind wave development under orographically modified winds. Combined use of QuikSCAT and SAR allows us to capture the surface wind transition from the shore to the offshore. They verify that the wind jets and wakes are extensions of terrestrial gaps and blockages. Variations of significant wave height observed by the altimeters are compared with those of surface wind derived from QuikSCAT and SAR along the altimeter ground tracks. The positions of local maxima and minima of significant wave height and squares of wind speeds coincide with each other. This demonstrates an important role of coastal topography in wind modification and the resulting offshore wind wave development.