Very large floods in the Brahmaputra river in August 1962 Part I: Synoptic aspects

Abstract

The large-scale synoptic situations from the time of onset of the southwest monsoon to the end of August in 1962 over the catchment of the Brahmputra (including that of the Tsangpo) heavy been studied using the synoptic charts prepared in India and those published by the Japan Meteorological Agecy. Time-sections of the upper winds over Gauhati (26° 11 ' N, 91o 45' E) and of the heavy rainfall at the India Meteorological Department stations over the Brahmaputra basin were also studied for all important situation .It has been shown that the lee-vortices which develop to the southeast of the Tibetan plateau play a. very important role in the occurrence of very heavy rainfall over and near Pasighat (28° 06' N, 95° 23' E) in the extreme northeast of Arunachal Pradesh and over the eastern half of the Tsangpo. The conclusion is drawn that frequent and exceptionally heavy rainfall over these area was predominantly responsible for the phenomenal discharge of the Brahmaputra at Pandu near Gauhati on 24 August 1962. The genesis of the lee-vortices to the southeast of the Tibetan plateau has also been discussed .The need for the development of synoptic climatology of the above-mentioned area with special reference to weather over the Brahmaputra basin, is pointed out.