SAR and MODIS images of atmospheric solitary waves generated by upstream blocking in flow over St. Lawrence Island Bering Sea

摘要

A group of atmospheric solitons is identified on a RADARSAT-1 synthetic aperture radar (SAR) image and a Moderate Resolution Imaging Spectroradiometer (MODIS) image taken about 4.5 hours later on June 6, 2001. On both images, this group of solitons is showed as dark-bright linear features. The atmospheric solitons are generated at St. Lawrence Island in Bering Sea and propagate against the airflow in the upstream direction. On the first SAR image, there are only three wave crests. However, on the second MODIS image, the wave train propagates further upstream and seven wave crests can be identified. The basic properties of this group of solitons are measured and derived. Radiosonde data show that the Froude number is close to unity. Therefore, theoretically, this phenomenon can be described by the classic "flow over bump" model and analyzed using the classic KdV equation.