Interannual Variability of Monsoon Precipitation and Local Subcloud Equivalent Potential Temperature

The interannual variability of monsoon precipitation is described in the context of a convective quasiequilibrium framework. Using two reanalysis products and two global precipitation datasets, the authors examine linear relationships between seasonal anomalies of precipitation and subcloud equivalent potential temperature (ueb) local to six monsoon regions. This approach provides a single near-surface thermodynamically relevant variable over both land and ocean, extending previous studies of interannual monsoon variability that emphasized ocean surface temperatures. After removing the variability linearly associated with an index of the El Ni~ no–Southern Oscillation, positive monsoon precipitation anomalies are shown to be associated with enhanced ueb local to and slightly poleward of the climatological ueb maximum. The variations in continental ueb local to the monsoon precipitationmaxima are mainly due to variations in subcloud specific humidity, with changes in subcloud temperature having the opposite sign. Motivated by the fact that some of these subcloud humidity anomalies occur over deserts poleward of monsoon regions, the relationship of 700-hPa flow with precipitation is examined, and enhanced precipitation in several regions is found to covary with the properties of shallowmeridional circulations. The implications of these results for the understanding of monsoon interannual variability are discussed.