Impact of springtime Himalayan-Tibetan Plateau snowpack on the onset of the Indian summer monsoon in coupled seasonal forecasts

摘要: The springtime snowpack over the Himalayan–Tibetan Plateau (HTP) region and Eurasia has long been suggested to be an influential factor on onset of Indian summer monsoon. To assess impact realistic initialization snow HTP monsoon, we examine a suite coupled ocean–atmosphere 4-month ensemble reforecasts made at European Centre for Medium-Range Weather Forecasts, using their Seasonal Forecasting System 4. were initialized 1 April every year period 1981–2010. In these seasonal reforecasts, is “realistically” with ERA-Interim/Land Reanalysis. addition, carried out additional set forecasts, identical in all aspects except that initial conditions snow-related land surface variables are randomized. We show high depth influences meridional tropospheric temperature gradient reversal marks monsoon onset. Composite difference based normalized index reveal that, years, (1) delayed by about 8 days, (2) negative precipitation anomalies warm prevail India. half this delay can attributed region. further demonstrate depths not uniquely influenced El Nino-Southern Oscillation, Ocean Dipole or North Atlantic Oscillation.