Abstract
In India, summer monsoon rainfall during June-July-August-September (JJAS) along the river Ganga is the lifeline. Since its variability predominantly affects the agriculture production, drought and flood over the densely populated meteorological subdivisions of the Gangetic West Bengal, Jharkhand, Bihar, East and West Uttar Pradesh. Owing to its importance, a large number of research on the variability of Indian Summer Monsoon Rainfall (ISMR) has been conducted. However, the types of rainfall (or precipitation), i.e. Large Scale Precipitation (LSP) and Convective Precipitation (CP), is less discussed. The LSP is precipitated out from the stratus or nimbostratus clouds, while CP occurs from the cumulus and cumulonimbus clouds, and both of them coexists during summer monsoon months. The current research aims to know the climatological characteristics and possible cause of occurrence of these two types of precipitation over the meteorological subdivisions. For this purpose, the data of LSP, CP, zonal, meridonal (u and v component) wind and Relative Humidity (RH) at the spatial resolution of 0.25° x 0.25° (25km) for the period of 1980-2019 are taken from the European Centre for Medium-Range Weather Forecasts (ECMWF), UK. The Outgoing Longwave Radiation (OLR) data at a surface resolution of 1° x 1° for the same months and periods are obtained from the National Centre for Environmental Information (NOAA), USA. The observed rainfall data of the India Meteorological Department (IMD) at the same resolution and period is considered and compared with ERA data. The spatial and temporal distribution of both types of precipitation is analyzed as well as their linkage with OLR, zonal winds and RH at pressure levels of 1000, 850 and 700hPa is examined.
Increased sporadic extremes decrease the intraseasonal variability in the Indian summer monsoon rainfall
