11-Indian droughts-quasi biennial oscillations of stratospheric winds.

Abstract

In his earlier paper klianjit Singh, 1986), the author has shown that between 1964 and 1975, there had been five occurrences of drought in India. They have coincided on four occasions with the easterly phase of the quasi biennial oscillation (c41310) of the lower stratospheric winds over Gan Island (0°41'S, 73°09'E), an equatorial station in the Indian lonaitudes. It was also shown, that, the westerly and easterly phases of the stratospheric winds modify the tropospheric circulation features, and therefore, form the best parameter for forecasting as well as monitoring the performance of the SW monsoon rainfall over India.

Tho Gan I station has stopped taking upper air observations from 1975. Time sections of Singapore and Nairobi were prepared for winds at 50 hPa and 30 hPa for the years 1975 to March 1987. It was seen that the longitudinal differences in phase of the equatorial circulation are small enough and we may use the stratospheric wind data of Singapore (1°22'N, 103°55'E) to forecast and monitor the behaviour of SW monsoon over India. It was found that droughts occurred in 1979, 1982, 1985, 1986 and 1987 and on four occasions they coincided with the easterly phase of the stratospheric winds over Singapore.