A global perspective of Southern Asian Monsoon annual mean precipitation variations in the Global Precipitation Climatology Project analyses (1979–2006)

Variations of annual mean precipitation in global monsoon regions are investigated with a focus on the southern Asian monsoon region using the Global Precipitation Climatology Project (GPCP) precipitation analyses over the period of 1979-2006. The El Niño Southern Oscillation (ENSO) is shown to dominate the variations especially in the Asian-Australian oceanic and archipelago and South Pacific Convergence Zone (SPCZ) monsoon regions. A precipitation increase in the regions is also shown. Focusing on the southern Asian monsoon region, it is found that the variations in the region may arise from non local oceanic and land forcing. Precipitation in the monsoon region is primarily driven by the meridional temperature gradient between the equatorial Indian Ocean and land region in India-China near 30°N latitude. It is shown that the gradient and precipitation increase concurrently over the 28-year period. Changes in the gradient are dynamic in nature with a higher rate of increase in surface temperature over land than over the equatorial Indian Ocean resulting in a higher surface temperature gradient between the regions.