Observations of Atmospheric Gravity Waves over the Chinese Seas by Spaceborne Synthetic Aperture Radar

On synthetic aperture radar (SAR) images acquired over the ocean often sea surface signatures of atmospheric gravity waves (AGWs) as well as of oceanic internal waves are visible. They often look quite similar and it is not always easy to decide whether the wave-like patterns result from AGWs or from oceanic internal waves. In this paper we present criteria how to discriminate between these two phenomena on SAR images of the sea surface. We present 4 SAR images acquired by the Advanced SAR (ASAR) onboard the European Envisat satellite over the China Seas showing sea surface signatures of AGWs. By using other satellite data and radiosonde data, we show that the wave-like patterns visible on the SAR images are indeed sea surface signatures of AGWs. From the SAR images quantitative information on the sea surface wind fluctuations induced by the secondary airflow associated with the AGWs are derived.