Tropical Indian Ocean Mediates ENSO Influence Over Central Southwest Asia During the Wet Season

Abstract:

El Niño-Southern Oscillation (ENSO) modulates wet season (November–April) precipitation over Central Southwest Asia (CSWA), however, intra-seasonal characteristics of its influence are largely unknown. Here we revisit the ENSO-CSWA teleconnection and note that it varies intra-seasonally and is a combination of direct and indirect positive influences. The direct influence is through a Rossby wave-like pattern but is only limited to the tail months. The indirect influence is through an atmospheric dipole of diabatic heating anomalies in the tropical Indian Ocean (TIO) as a result of ENSO-forced response, which also generates a Rossby wave-like forcing and persists throughout the wet season. ENSO exerts its strongest influence when both direct and indirect modes are in phase, while the relationship breaks down when the two modes are out of phase. The atmospheric teleconnection through the atmospheric diabatic heating anomalies in the TIO is reproducible in a numerical model simulation.