The sea surface imprint of island lee waves as observed by RADARSAT synthetic aperture radar

As stratified air flows over a mountain or an island, it often sets up large standing atmospheric gravity waves called atmospheric lee waves. This type of wave can carry aircraft upward or downward, sometimes causing serious safety problems. There are two types of lee wave patterns: (1) the transverse wave type where the wave crests are nearly perpendicular to the wind direction; and (2) the diverging wave type where the wave crests are orientated outwards from the center of the wake. The atmospheric lee waves are often associated with cloud patterns, which can be imaged with various visible remote sensors. Since the atmospheric lee waves modulate the sea surface wind field, and thus modulate the sea surface roughness, these waves can also be observed over the open ocean in SAR images. In this study, we analyze the diverging atmospheric lee wave pattern found in two RADARSAT SAR images. The first one is near Kodiak Island in the Gulf of Alaska taken on June 27, 1997. The second one is near St. Lawrence Island in the Bering Sea taken on August 4, 1997. There are two groups of atmospheric lee waves behind two islands south of Kodiak Island and four groups of diverging wave patterns imaged by the RADARSAT SAR on the lee side of the four major mountains of St. Lawrence Island. We consider the island mountains as point sources that generate atmospheric lee waves