Spatial-temporal variation and mechanism associated with mini-cold pool off the southern tip of India during summer and winter monsoon season

Abstract

Sea surface temperature (SST) from different sources suggests that the occurrence of a mini-cold pool (MCP) off the southern tip of India (STI) is a persistent phenomenon which occurs during both the summer and the winter monsoon seasons. However, the associated mechanism is different in both scenarios and, hence, numerical experiments are conducted to study and ascertain the mechanism. The dynamics that govern the occurrence of MCP during the summer season is mainly due to upwelling, caused by the divergence in the near-surface circulation off STI, advection of the cold upwelled water from the western Arabian Sea and the southwest coast of India. In contrast, during the winter monsoon, the model studies suggest that circulations driven by positive Ekman dynamics and outgoing heat flux are mainly responsible for the formation of MCP off STI during December–February. The cold water intrusion in both seasons occurs in accordance with the monsoon and coastal currents, which underlines the importance of advection. The position and extent of cooling differs during both seasons because wind stress varies significantly.