Influences of the Indian ocean dipole on the asian summer monsoon in the following year

By exploring the spatiotemporal features of the Indian Ocean Dipole (IOD) both on the sea surface and in the subsurface ocean, the present article reveals that the subsurface dipole mode, with larger amplitude than the surface one, is likely to prolong the dipole signal for a long time. Using the wind and geopotential height data from NCEP/NCAR, this article further investigates IOD impacts on the Asian summer monsoon activities in the following year. A normal (late) South China Sea summer monsoon onset is associated with the previous positive (negative) IOD. In the summer after an IOD year, a positive (negative) IOD tends to induce a stronger (weaker) 100-hPa South Asian High, with a more (less) eastward-extending high ridge, and also an enhanced (a weakened) 500-hPa western Pacific subtropical high, with a westward-advancing (an eastward-retreating) high ridge. Influenced by the anomalous 850-hPa Asian monsoon circulations and the longitudinal position of the 500-hPa subtropical high ridge, summer rainfall in China also exhibits different patterns corresponding to different phases of the IOD in the previous year. Copyright © 2008 Royal Meteorological Society.