Utility of INSAT 3D / 3DR products in understanding the physical processes in clouds associated with western disturbance affecting North India during winter

Abstract

ABSTRACT Images obtained from five wavelength channels of Indian National Satellite (INSAT)-3D/3DR were utilized to interpret the nature of clouds associated with a Western Disturbance (WD) over north India during the winter season. Physical parameters like its shape, size, shadow, highlight and cloud toptemperature were studied to extract information on its type and vertical extent. The nature of clouds in the different sectors within the cloud mass, associated with the WD were related to geopotential thickness (gpm), total precipitable water (TPW) and vertical velocity. This was compared with the precipitation index (3 hour accumulated) and spatial distribution of precipitation. Spatially, there is a pronounced east-to-west gradient in the thickness, with strong upward velocity, which reaches its maximum at 500 hPa. Decrease in thickness, increase in TPW and increase in vertical velocity at 500 hPa plays a very important role in the formation of different type of clouds either convective or stratiform (liquid, mixed or ice phase). Across north India, vertical velocity over hilly terrain is substantially larger than that seen over the plains. This aspect has a substantial effect on the type of clouds and intensity of precipitation. The precipitation was estimated using the quantitative precipitation estimation (QPE) technique, which overestimated precipitation, when it was moderate or heavy and was within acceptable limits when the precipitation was light.