Revisiting the relationship between the South Asian summer monsoon drought and El Niño warming pattern

Abstract

AbstractBased on the observational and reanalysis data, El Niño warming patterns associated with the South Asian summer monsoon droughts are investigated. While the inverse relationship between the eastern Pacific (EP) type of El Niño‐Southern Oscillation (ENSO) and the Indian monsoon rainfall weakened significantly, the correlation between the central Pacific (CP) type of ENSO and the monsoon rainfall strengthened after the late 1970s. Moreover, the drought‐producing El Niño warming pattern also exhibits a notable decadal modulation associated with the climate shift. The analysis results indicate that both the EP type of El Niño with positive sea surface temperature (SST) anomalies extended to the date line and the CP type of El Niño with the maximum warming located in the central equatorial Pacific may produce severe droughts over the Indian subcontinent. Although the CP warming is more effective in driving anomalous rising motion in the central equatorial Pacific and consequently producing anomalous subsidence over South Asia, the position and strength of the anomalous ascending and descending branches of the Walker circulation are sensitive to the detailed distributions of tropical SST anomalies and determined by the competing effects of the CP and EP warming.