An interesting case of persistent rain cells observed by RISAT-1 SAR over the Indian Ocean during a pair of depression–cyclone interactions (August, 2012)

Abstract

ABSTRACT It is well known that rain cells leave footprints on the sea surface that sometimes become visible on Synthetic Aperture Radar (SAR) images. However, it is rare to be able to track the same raincell on subsequent optical satellite images, owing to the dynamical nature of the precipitation. In August 21–26, 2012, there were long distance multiple interactions between two, category-4 typhoons: Tembin and Bolawen, and two Tropical Depressions (TD) in Pacific Ocean. The rapid uplift of air masses due to these interactions coupled with the establishment of Asian Monsoon anticyclone led to the formation of small scale raincells in Indian Ocean as observed by RISAT-1 SAR. The raincells with spatial dimension of the order of ~3 km associated with precipitation (> 13 mm hour−1) and the significant wind speed changes of (~5 m s−1) are seen to propagate towards Eastward direction. Later (after 5 hours), they are observed in MODIS Cloud Microphysical product. The novelty of the study lies in its approach to use an opportunistic synergy of independent sensors observing in different spatio-temporal and spectral domain to understand complex atmospheric interactions resulting in a peculiar phenomenon, which otherwise cannot be detected or resolved using single source information.