Nocturnal offshore propagating precipitation systems (NOPS)

NOPS concept can be generalized over all Asian monsoon regions.

· Indian region

Indian Monsoon region

A cartoon that shows NOPS along the southeastern coast of India.

The schematic diagram summarizes the influence of monsoon low-level winds and gravity waves on the eastward propagation of the diurnal precipitation peak over southeast India. In this schematic model, we explain the diurnal strengthening of monsoon southwesterly winds over the southeast coast onshore (offshore) regions that support inland (near the coast) afternoon/evening (night/late night) diurnal peaks around 1500–1800 LST (0100–0400 LST). The presence of a strong anomalous westerly in the lower atmosphere (900 hPa) at night strengthens near the land–sea boundary along the southeastern coast. Late at night, an atmospheric gravity wave causes the nocturnal diurnal wave to propagate eastward from the southeast coast offshore, following the gravity wave propagation speed. Precipitating clouds differ according to the development mechanism of precipitation systems; for instance, southeast India experiences mainly stratiform clouds, and southwest India experiences deep convective clouds. Therefore, diurnal variations and propagation to the leeward side of the WGs are determined by the interaction between monsoon low-level southwesterly winds and gravity waves.

NOPS over Asian monsoon regions (In preparation)

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This figure shows highest diurnal variability over the asian region along the coasts. As per the concept these high variability precipitation regions are the nocturnal offshore propagations.