Differences in the structure and evolution of the atmospheric boundary layer over coastal and inland stations

Differences in the structure and evolution of the atmospheric boundary layer over coastal and inland stations. A. Sandeep and T.N.Rao National Atmospheric Research Laboratory, Gadanki – 517 112, India. The atmospheric boundary layer (ABL) is the layer just above the surface, influenced strongly by the exchange of momentum, mass and energy across the surface. The surface forcing depends on several factors starting from geography to surface characteristics and to dynamics of the atmosphere at lower levels. The ABL characteristics at coastal station, therefore, could be different from that of an inland station. For example, the surface near the coast is rich in soil moisture compared to an inland station and also the coastal regions are generally under the influence of sea-breeze and thermal internal boundary layer circulations. To understand the differences in boundary layer structure and characteristics over coastal and interior regions, two L-band wind profiler were employed. A portable wind profiler operating at a frequency of 1.28 GHz was installed at IGCAR, Kalpakkam, nearly 7 km away from the Bay of Bengal. It was operated continuously for 6 months (September 2010 through February 2011), covering postmonsoon and winter seasons (September is an exception, which falls in southwest monsoon season). A fixed L-band radar was operated at Gadanki, which is about 90 km from the coast, an inland station situated in a complex terrain. The design and frequency of both radars are same, except for that the fixed radar is big in size and transmits relatively more power. An adaptive data processing software has been used to obtain the basic parameters (winds, backscattered power, turbulence, boundary layer height) and they were used to understand the differences in ABL characteristics between a coastal and an inland station. Special emphasis was put on the Low Level Jet, an integral part of the monsoon circulation.

Address for Correspondence Araveti Sandeep Research Scholar National Atmospheric Research Laboratory, Box 123, S V U Campus, S V Univerisity, Tirupati – 517 502. Email: aravetisandeep@narl.gov.in Fax: 08585 272018