Changes in the mechanism of the South-Asian summer monsoon onset propagation induced by the pre-monsoon aerosol dust storm

Abstract

A modeling effort is considered to understand the effect of dust aerosol storms in the Indian summer monsoon (ISM) onset propagation over the Indian subcontinent. The study found how the dust aerosol loading during the pre-monsoon period over the Indian subcontinent positively impacts the advancing ISM onset. The heavy loading of dust aerosol from middle east Asia to the northwest (NW) Indian region boosts the temperature gradient over the mid-troposphere. This sudden rise in the mid-tropospheric atmospheric temperature triggers the low-pressure belt over the monsoon trough. It amplifies the Elevated Heat Pump mechanism and loads enough dust for the dust storm over north India. The formation of the monsoon trough over the Indo-Gangetic Plain (IGP) pulls the moisture-loaded wind towards the Indian subcontinent and the IGP, followed by the onset of monsoon over Kerala within a week. Due to this storm, the intense heat gradient in the troposphere also induces the monsoon propagation and the monsoon advancement from Kerala to BoB within a short time. However, it makes up for the naturally delayed monsoon on time. Plain language summaryStudy shows how the pre-monsoon dust storm modulates the Indian summer monsoon (ISM) propagation over the Indian region. The onset of the monsoon was delayed in a particular year, and the pre-monsoon dust storm over northwest India changed the regular monsoon mechanism and generated an entirely different mechanism. The elevated heat pump theory applies that pushes the monsoon advancement faster than usual. A dust storm over north India causes a sudden rise in the mid-tropospheric temperature gradient and more rapid monsoon advancement than usual.