Diurnal variability of atmospheric cold pool events and associated air-sea interactions in the Bay of Bengal during the summer monsoon

Atmospheric cold pools generated from convective downdrafts can significantly modulate air-sea interaction processes, though the variability in cold pool events is not yet documented in the Bay of Bengal (BoB). In this study, the seasonal and diurnal variability of cold pool events (defined as a drop in air temperature greater than 1 degrees C within 30 min) in the BoB is examined using moored buoy measurements with 10-min temporal resolution at 8 degrees N, 12 degrees N, and 15 degrees N along 90 degrees E. The analysis shows that cold pools are plentiful and frequent during summer (May-September) and fall (October-November) compared to winter (December-February) and spring (March-April). Results also indicate a significant diurnal variability at 15 degrees N and 12 degrees N (but not at 8 degrees N) during summer, with more frequent and intense cold pool events in the afternoon. Cold pools lead to an intensification of turbulent heat exchange between the ocean and atmosphere, with increased latent heat loss (similar to 80 Wm(-2)) through both an increase in wind speed and reduction in air specific humidity and increased sensible heat loss (similar to 40 Wm(-2)) due primarily to air temperature drops. There is also a significant diurnal variability in these air-sea exchanges during the summer, with a twofold enhancement in latent and sensible heat fluxes associated with afternoon vs nighttime cold pools events. Finally, we establish the connection between the enhancement of afternoon cold pool events and southeastward propagating synoptic-scale rainfall activity on diurnal time scales from the western BoB.

Automated summary

This study examines the seasonal and diurnal variability of cold pool events in the Bay of Bengal using moored buoy measurements. Results show that cold pools are abundant and frequent in summer and fall compared to winter and spring. Cold pools intensify heat exchange between the ocean and atmosphere, leading to increased heat loss, and exhibit significant diurnal variability during summer at certain latitudes.