ENSO Modulation of Interannual Variability of Dust Aerosols over the Northwest Indian Ocean*

Abstract

Abstract Mineral dust is known to affect many aspects of the climate of the north Indian Ocean (IO). However, what controls its interannual variability over this region is largely unknown. The authors study the mechanism controlling the interannual variability of dust aerosols in the principal dust belts bordering the northwest IO. It is shown that annual dust activity to the north of the Persian Gulf has an inverse relation with preceding precipitation during October–December and soil moisture during current dust season (April–August). These are in turn remotely controlled by El Niño–Southern Oscillation (ENSO) through the modification of the intensity of convection over the Indo-Pacific warm pool region, which affects moisture flux to the dust sources. While La Niña leads to a negative precipitation anomaly and more dust generation during the following summer, El Niño is responsible for the opposite. During the summer following La Niña, the air–sea interaction leads to a lowering of geopotential height over the Indo-Iranian region, resulting in an increased gradient between the Indo-Iranian region and the surrounding regions. This intensifies the dust-transporting northwesterly and northeasterly winds over the Arabian Peninsula. The dust transport by the intensified low-level southwesterlies and upper-level westerlies is the main factor responsible for enhanced dust over the open northwest IO during the years following La Niña. The Indian Ocean dipole potentially impacts the variability of dust over the northwest IO by modifying the moisture associated with El Niño.