Observation of Double-mixing Line Structure in the Convective Boundary Layer During the Summer Monsoon Season

Abstract

Ð The special aerological observations carried out as a part of Land Surface Processes Experiment (LASPEX) were used to investigate the thermodynamic structure of the convective boundary layer during the summer monsoon of 1997. The analysis suggested that the convective boundary layer top was found at 700 hPa which was associated with h e minimum and h es maximum values. Double-mixing line structure was noticed in the conserved variable diagrams which was possibly attributed to the radiative warming/evaporation of falling precipitation.

Observations of the thermodynamic structure of marine atmospheric boundary layer over Bay of Bengal, Northern Indian Ocean and Arabian Sea during premonsoon period

“…For P SPD values greater than zero, the parcel is saturated and negative P SPD shows the sub-saturation (Betts, 1982). When the absolute magnitude of P SPD is observed to be less than 50, it is usually associated with cloud layers (Murthy and Parasnis, 2002). The parameters discussed above are used to delineate the various layers in the MABL, namely (a) surface layer, which generally varies from surface to about 100 m, also known as the constant flux layer, (b) mixed layer or sub-cloud layer, which varies from the top of the surface layer up to about 100 m below the cloud base, where due to turbulent mixing potential temperature and specific humidity remains more or less uniform, (c) transition layer-marked by a stable potential temperature and decrease in moisture content, (d) cloud layer-which extends from the cloud base to the base of the inversion, and characterized by nearly adiabatic lapse rate and decreasing moisture content with altitude, and (e) inversion layer; which tops the tropical boundary layer during the undisturbed conditions, having highly stable temperature gradient and sharp decrease in specific humidity (Garratt, 1992;Gupta and Radhika, 1998).…”