Aerosol dipole pattern over India: consequences on rainfall and relation with wind circulations

The aerosol concentrations are changing in rapid phase in the recent decades over Indian subcontinent. A general conclusion that is postulated from various studies indicated high aerosol loading over the Indian subcontinent. The aerosol concentrations are found to alter cloud-precipitation chemistry globally. Analysing the trends of aerosol concentrations over the Indian subcontinent is crucial to understand in depth the aerosol–precipitation relationship over these regions. In the present study, the long-term trend (2000–2019) of aerosols, precipitation and winds has been analysed over the Indian subcontinent. The work aims to identify the zones of significant increasing/decreasing Aerosol Optical Depth concentrations and alter the rainfall patterns over these regions. Mann–Kendall test has been employed for trend analysis. An aerosol dipole pattern is observed along the eastern-western boundaries of the monsoon trough over the Indian subcontinent (India, Bangladesh and Pakistan), which shows an inverse relationship with the rainfall patterns. Over the north-western region of the Indian subcontinent, the reduced pollution and enhanced precipitation may further alter the land-sea thermal gradient, resulting in the weakening of monsoonal circulation. Enhanced pollution over eastern India is adjusting the precipitation distribution along with the weakening of low-level jet and moisture transport. The present study provides an evidence of aerosol–precipitation relation over the Indian subcontinent using long-term datasets that has profound application in better understanding the weather systems.