Rain Cells Associated with Atmospheric Fronts over the Ocean Studied by Spaceborne Sar and Weather Radar Data

Spaceborne SAR images acquired over the ocean in conjunction with weather radar images are well suited to study atmospheric fronts in coastal areas. In this paper we confine ourselves to study quasi-stationary atmospheric fronts off the east coast of Taiwan which are located typically 3070 km offshore. These quasistationary atmospheric fronts were first detected on ERS SAR images [5]. In [5] we have compared mainly ERS SAR images with cloud images from a geostationary satellite, while here we compare Envisat ASAR and MODIS images mainly with weather radar images. Our analysis of three events presented in this paper lends further support to our hypothesis that these coastal quasi-stationary atmospheric fronts are generated by the collisions of the two airflows from opposing directions: one is associated with a weak to moderate easterly synoptic-scale wind blowing against the high coastal mountain range at the east coast of Taiwan and the other with a local offshore wind. The offshore wind results from re-circulated air flow from the synoptic-scale onshore wind and not primarily from a land breeze/katabatic wind system. However, this diurnally varying wind system has a modulating effect on the quasi-stationary atmospheric front.