High-Level Warmings, Winds and Indian Summer Monsoon

Abstract

Temperature and wind data for the troposphere, stratosphere and mesosphere obtained from rocket-sonde/radiosonde/rawin observations made at a tropical station (Thumba, 8°32?15?N, 76°51?48?E) during five summer monsoons (1971?73, 1975?76) with differential monsoon activity were examined. There is agreement between the occurrence of high-level warmings and monsoon activity in four out of five monsoons studied. There were no warmings in the year with very weak monsoon activity. The temperatures of the stratopause and the tropopause were significantly warmer in 1972 when the monsoon was very weak than in other years when the monsoon was active or very active. There is a high positive correlation between the monsoonal activity (precipitation departure from normal over Indian subcontinent) and the 25 km mean zonal wind, and a strong negative correlation with the winds near 16 and 50 km. The change in the sign of correlation coefficient was due to the observed phase change with altitude of the quasi-biennial oscillation. The study indicated the possibility of a relationship between stratospheric quasi-biennial structure and the Indian monsoon rainfall.