A Study on the Influence of Synoptic-Scale Flows on Sea Breeze During Wintertime in the Coastal Zone Near Visakhapatnam, India

Abstract

The present study focuses on the influence of prevailing winds (like onshore, offshore and alongshore) on sea breeze flow over the coastal station Visakhapatnam (17.7 ° N, 83.3 ° E). The database consists of sodar observation relative to 58 sea breeze occurred during the winter season (December 2011-February 2012). Results show that the strength of sea breeze are modulated by the large-scale wind flow and show substantial changes between offshore, along-shore and onshore. The role of thermal forcing on the breeze circulation was investigated. Results show that temperature difference between land and sea (ΔT) is larger for offshore and along-shore when compared to that of onshore flow. Results reveal that the vertical velocities show downdrafts and updrafts just before and after the onset of sea breeze. The depth of sea breeze is found to be higher (~220 m) for the offshore than onshore large scale circulation (~160 m). It is found that offshore and alongshore favours the delayed arrival of sea breeze compared to that of onshore. The statistical analysis of sea breeze circulation addressed in this work highlight the distinct behavior in the structure and evolution of sea breeze using high temporal and vertical resolution of sodar observations under different synoptic-scale wind flow. Such statistical results are sparse over the industrialised coastal zones like Visakhapatnam where air pollution is a major concern, as well as for better understanding on the vertical mixing of aerosols and trace gases, and air-pollution dispersal.