Effect of Tibetan spring snow on the Indian summer monsoon circulation and associated rainfall

In this communication, the effect of Tibetan snowfall in the month of April on the Indian summer monsoon circulation and associated seasonal rainfall has been examined using the Regional Climate Model version 3. This model has been integrated at 55km horizontal resolution from April to September in each of the years from 1993 to 1996. NIMBUS-7 SMMR snow depth data have been used as boundary conditions. Sensitivity experiment shows that Tibetan snow results in weak lower level monsoon westerlies and upper level easterlies. Without any initial snow, the sensible heat flux is found to be more, whereas with snow, the latent heat flux is more over the Tibetan region. Results indicate that the Indian Summer Monsoon Rainfall is reduced over entire India and its five homogeneous zones, when 10 cm of snow has been introduced over the Tibetan region in the preceding month of April. Quantitatively, rainfall decreases by 30% for all India, 23% for northwest India, 20% for west central India, 25% for central northeast India, 30% for northeast India and 15% for south peninsular India.