Interannual Variability of Indian High Intensity in Boreal Winter

Abstract

This study investigates the interannual variability of the boreal winter Indian High (WIH) intensity from 1979 to 2023 and explores its causes. Observational results show that WIH intensity peaks at a quasi‐4‐year period with a slight increase over time. The WIH significantly influences temperature and precipitation across the Indian Ocean and adjacent regions during boreal winter. This variability is primarily driven by sea surface temperature anomalies (SSTs) in the Indian and Pacific Oceans. Typically, when SSTs in the western Pacific and southeastern Indian Ocean are cooler, and those in the eastern Pacific and western Indian Ocean are warmer than average, a stronger WIH occurs. The positive correlation between SST anomalies and WIH intensity can persist from the preceding autumn into winter, peaking in late autumn to early winter. A critical physical process involves the interaction between the warm phases of the El Niño‐Southern Oscillation (ENSO) and the associated Indian Ocean dipole mode, which favors the formation of a North Indian Ocean anomalous anticyclone (NIOAAC). This leads to significant easterly anomalies near the Equator and enhances the regional Hadley cell. Consequently, positive geopotential anomalies associated with the NIOAAC within the 50°–100°E, 0°–20°N region strengthen the WIH. Numerical simulations confirm this key physical process.