Airmasses upto 500 mb level over the Indian summer monsoon trough area

Abstract

. Rao and Desai (1973) have indicated the nature of airmasses present over India and neighbourhood during July-typical monsoon month-on the basis of India Met. Dep. Forecast. Manual Part 1-2. "Climatology of India and neighbourhood-Climate of India (1968)". In the publication "Upper Air Atlas of India and Neighbourhood" (India Met. Dep. 1972), are given (i) Normal upper air temperature and contours and (ii) Normal upper winds from which one can draw inferences about airmasses over the area. Ramage and Raman (1972) have given 850, 700 and 500 mb charts for July in Voi. 2, Upper Air Meteorological Atlas of the International Indian Ocean Expedition (IIOE) from which also inferences can be drawn about airmasses over the area in question. It is seen from India Meteorological Department (1972) upper winds charts and charts of Ramageand Raman(1972) that the axis of the monsoon trough, which extends from near Delhi to Calcutta at the surface and slope southwards with height, has on both sides the air of continental origin while according to Rao and Desai and India Meteorological Department (1972) normal upper air temperature and contour charts, the axis of the monsoon trough at 850 and 700-mb levels has moist air of oceanic origin on both sides.

The chart showing distribution of rainfall over India during July would not appear to support the inferences about airmasses drawn from charts of Ramage and Raman and India Meteorological Department upper wind charts.