Use of INSAT winds for better depiction of monsoon depression over Indian region

This study is aimed at evaluating the impact of non-conventional winds using data obtained by INSAT satellites over the Indian region. The emphasis is on whether the satellite-derived wind data improve the depiction of monsoon system, flow patterns, the centre of the system, etc. in the objective analysis of the wind field. For this purpose, monthly climatological normals of the wind field are considered as the initial guess field and then objective analyses of the wind field are performed, first using only conventional winds over the land areas and subsequently including winds constructed from cloud-motion vectors at 850 and 700 hPa. This experiment was performed for the period of 19–21 September, 1991, when a monsoon depression formed over the Bay of Bengal. Verification of these analyses were made by comparing them with carefully drawn subjective analyses. It is inferred that INSAT winds have a positive impact on the objective analysis, and improvement in the analysis is more marked over the data-void regions of the Arabian sea and the Bay of Bengal. The results presented in the study reveal that INSAT winds are of potential use in the objective analysis of the wind field, thus giving a better depiction of monsoon depression over the Indian region