Recent two decades witness an uptick in monsoon depressions over the northern Arabian Sea

The analysis reveals that the occurrence of summer Monsoon Depressions (MDs) over the North Arabian Sea is doubling during 2001–2022 compared to the 1981–2000 period. This increase stems from changes in the region’s dynamic and thermodynamic conditions. The heightened genesis potential parameter with sea surface temperature and moisture flux transport and its convergence over the North Arabian Sea inducing MDs formation, contrasting to the Bay of Bengal. The dynamic processes involved in its formation, a combination of barotropic and dynamical instability, are leading to increased rainfall over northwestern India. Strong East Asian jet variability, with an anomalous anticyclone in the north and weak cyclonic anomalies in the south, induces prevailing easterly wind anomalies along the monsoon trough. This leads to a poleward shift (~1.13°) in the low-level jet, significantly altering dynamic and thermodynamic parameters in the northern Arabian Sea region leading to a notable increase in MDs.

Nagaraju Chilukoti, Mahendra Nimmakant, Jasti S. Chowdary