Analysis of island wakes and katabatic winds imaged by RADARSAT-1 synthetic aperture radar

摘要

In this study, the sea surface imprints of strong mountain katabatic winds and gap winds are observed on RADARSAT-1 synthetic aperture radar (SAR) ScanSAR wide images off the west coast of the U.S. and in the Gulf of Alaska. Two case studies are presented. In the first case study, a RARASAT-1 SAR scene taken at 14:25:30 UTC on January 21, 2003 shows a finger-like wind pattern that mirrors the coastal mountain height. In the second case, the SAR image was taken at 4:41:45 UTC on December 22, 1999. It shows a strong gap wind and vortex streets through the Aleutian Islands. In order to understand the dynamics of these wind patterns observed in the SAR images, we simulated the low level atmospheric circulation using the fifth-generation Pennsylvania State University (PSU)-National Center for Atmospheric Research (NCAR) Mesoscale Model, MM5. A triple nested-grid (9/3/1 km) technique is employed to achieve a multi-scale simulation. In general the MM5 model captures the wind pattern very well and reveals the dynamics of these meso-scale atmospheric phenomena. However, the MM5 did not resolve the vortex shedding due to the model resolution and the complex nature of this phenomenon.