Spatio-temporal variability in the stratiform/convective rainfall contribution to the summer monsoon rainfall in India

Spatio-temporal variability of contributions of stratiform and convective rainfall to Indian monsoon (June-September) rainfall have been investigated using hourly rainfall data of well distributed 126 stations in India for the period 1969-2015. The criteria used for identifying stratiform rainfall are hourly rainfall <= 5 mm and spatial homogeneity. The study showed that Indian monsoon rainfall exhibits two distinctive features, viz. stratiform component dominating over peninsular (southern) India and convective component dominating over northern India. The diurnal variation shows domination of convective activity in the afternoon hours over the northern parts of India. Intra-seasonal variability in the stratiform rainfall is the lowest over the West Coast stations through-out the season. While it shows low values during the onset (June) and withdrawal (September) phases of monsoon and higher values during July-August in Peninsular India. Inter-annual variations in the convective rainfall are larger than that of stratiform rainfall all over the country. Trend analysis indicates that both stratiform and convective rainfall are decreasing over the central parts of the country and increasing significantly along West Coast and western parts of the country. During excess monsoon year, convective rainfall activity is more than in deficit monsoon year, in Central India. The results brought out in the study will be useful as a proxy for understanding the spatial and temporal variability of the latent heating fields over India in the monsoon season and validation of model simulations of clouds and rainfall types.