Dynamical abnormalities associated with drought in the Asiatic summer monsoon

Abstract

In recent years 1965 and 1972 have been years of severe drought over India and neighbourhood. The dynamical and thermal features of these seasons are contrasted with those of normal monsoon, The main local abnormality during drought years is the shift of the monsoon trough northwards and development or anti-cyclones over central India in the lower troposphere. The main abnormality in the thermal field is that temperatures are considerably below normal over southern parts of USSR. Iran. Afghanistan and north India.

Quasi-geostrophic 'w' is used to delineate the vertical circulations. It is seen that the north-south circulation and associated energy conversion is weaker and the east-west circulation more marked during breaks. A model of the vertical circulations during drought periods is suggested.

The intensity phase movement and vertical and horizontal tilts of the different wave number in the mid-latitudes during drought and in the preceding months is contrasted with the normal, In 1972 wave Nos, 5.9 were abnormally pronounced and showed some dynamical differences.