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A diagnostic study on heat sources and moisture sinks in the monsoon trough area during active-break phases of the Indian summer monsoon, 1979

Bhide, UV and Mujamdar, VR and Ghanekar, SP and Paul, DK and Chen, TC and Rao, GV (1997) A diagnostic study on heat sources and moisture sinks in the monsoon trough area during active-break phases of the Indian summer monsoon, 1979. Tellus, Series A: Dynamic Meteorology and Oceanography, 49 (4). pp. 455-473.

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Abstract

The diabatic heating over the Indian monsoon trough area, along with its thermal structure are studied for the 1979 summer monsoon based on FGGE level-IIIb upper air data of the European Centre for Medium Range Weather Forecasts. The apparent heat source and the apparent moisture sink over the trough area varied coherently with the rainfall over central India. The spatial and temporal variations of the vertically integrated apparent heat source and moisture sink were found to be coincident. These coincidences suggested that diabatic heating was largely contributed by the latent heat released by cumulus convection. During the active periods, the vertical structure of spatially-averaged heating and drying rates above the monsoon trough area showed higher values, as much as 8 K to 11 K day-1, at the mid-tropospheric level (500hPa), but much smaller and even negative values during break periods. Analyses of the heating and drying rates at 500 hPa level in a x-t diagram revealed that heat sources and moisture sinks propagated westward across the trough area with a period of 10-15 days (often called monsoon mode). The 30-50 day period of fluctuations showed a close link with the two major active/break phases of monsoon during the season. The monsoon mode became a part of the mid-season fluctuation of monsoon activity between the two major active phases. This paper discusses the spatial distribution of rainfall and heat source and moisture sink over the trough area, and the role of east-west differential heating in the development of weak/break phases of Indian summer monsoon 1979.

Item Type: Article
Additional Information: Copyright of this article belongs to Tellus
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 21 Feb 2015 15:11
Last Modified: 21 Feb 2015 15:11
URI: http://moeseprints.incois.gov.in/id/eprint/1708

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