Thermodynamic structure of the atmosphere along East coast of India during BOBMEX-99

Abstract

Thermodynamic features of the Convective Boundary Layer (CBL) during the summer monsoon season of 1999 have been examined over the Indian east coastal stations with respect to the prevailing synoptic scale weather disturbances. For this purpose high resolution aerological observations specially collected during the Bay of Bengal Monsoon Experiment-99 for the Intensive Observing Periods (IOPs) for the six east coastal stations have been considered. Out of the five available IOPs observations during two IOPs, one during July and another during August, 1999, have been used to explore the differences in the CBL characteristics. The coastal stations are categorized into two groups based on the surface pressure distribution and the location of the stations with respect to the prevailing weather disturbance (either deep depression or low pressure area) viz., Gr.A (stations located in the vicinity of the disturbance with low surface pressure) and Gr.B (stations situated away from the disturbance and associated with high surface pressure) stations. The temporal variation of different thermodynamic parameters at the surface indicated more moist convective activity at the surface during August. The averaged vertical profiles of different thermodynamic parameters revealed more convective activity for Gr.A stations as compared to Gr.B stations during both July and August indicating the more influence of the existing disturbance on the stations situated in the proximity of the disturbance. However, the moist convective activity is more during July as compared to August, except in the surface layer, for both the groups. The CBL tops vary in the range 700-500 hPa. The conserved variable diagrams revealed single mixing line structure during both July and August for all the categories.