The recent heavy rainfall events over Chennai on Nov 15 – 16 and on Nov 30 – Dec 1, 2015 have provided an excellent opportunity to inter compare the rainfall estimates from satellites - GPM, INSAT – 3D; Chennai Doppler Radar and ground raingauges. The results show wide disparity between the various estimates, posing the basic question as to the spatio temporal scales at which any one could be a substitute for the other.
Our studies to inter compare TRMM merged rainfall products with IMD gridded rainfall over Indian land mass from 15 years of concurrent data, have shown that on daily scale, only beyond 5 x 5 deg spatial average, the two satellite estimates and ground measurements have semblance of compatibility. Details of this study which has been performed for different rain rates will be presented.
Dr M S Narayanan is at SRM University. He was group director SAC,ISRO,Ahmedabad. His research interest is on satellite remote sensing, with focus on monsoon rainfall.