Observation of Sea Breeze Front and its Induced Convection over Chennai in Southern Peninsular India Using Doppler Weather Radar

摘要

Sea breeze, the onshore wind over a coastal belt during daytime, is a welcoming weather phenomenon as it modulates the weather condition by moderating the scorching temperature and acts as a favourable mechanism to trigger convection and induce precipitation over coastal and interior locations. Sea breeze aids dispersal of pollutants as well. Observational studies about its onset, depth of circulation and induced precipitation have been carried out in this paper for the period April to September, 2004–2005 using a S-band Doppler Weather Radar functioning at Cyclone Detection Radar Station, India Meteorological Department, Chennai, India. The onset of sea breeze has been observed to be between 0900 and 1000 UTC with the earliest onset at 0508 UTC and late onset at 1138 UTC. The frequency is greater during the southwest monsoon season, viz., June – September and the frequency of initial onset is greater in north Chennai. The modal length of sea breeze is between 20 and 50 km with extreme length as high as 100 km also having been observed. Though the inland penetration is on average 10 to 20 km, penetration reaching 100 km was also observed on a number of cases. The induced convection could be seen in the range 50–100 km in more than 53% of the cases. The mean depth of sea breeze circulation is 300–600 m but may go well beyond 1000 m on conducive atmospheric conditions.