TITLE:
Variation of Zonal Winds in the Upper Troposphere and Lower Stratosphere in Association with Deficient and Excess Indian Summer Monsoon Scenario
AUTHORS:
Vazhathottathil Madhu
KEYWORDS:
Indian Summer Monsoon, Upper Troposphere/Lower Stratosphere, Zonal Winds
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.4 No.4,
October
23,
2014
ABSTRACT: The Indian summer
monsoon is one of the most dominant tropical circulation systems in the general
circulation of the atmosphere. The country receives more than 80% of the annual
rainfall during a short span of four months (June to September) of the
southwest monsoon season. Variability in the quantum of rainfall during the
monsoon season has profound impacts on water resources, power generation,
agriculture, economics and ecosystems in the country. The inter annual
variability of Indian Summer Monsoon Rainfall (ISMR) depends on atmospheric and
oceanic conditions prevailed during the season. In this study we have made an
attempt to understand the variation of the of zonal winds in the tropical Upper
Troposphere and Lower Stratosphere (UT/LS) region during deficient and Excess
rainfall years of Indian summer monsoon and its relation to Indian Summer
Monsoon Rainfall (ISMR). It is found that in the equatorial Upper Troposphere
zonal winds have westerly anomalies during deficient rainfall year’s and
easterly anomaly during excess rainfall years of Indian summer monsoon and
opposite zonal wind anomaly is noted in the equatorial Lower Stratosphere
during the deficient and excess rainfall years of Indian summer monsoon. It is
also found that the June to September upper troposphere zonal winds averaged
between 15°N and 15°S latitudes have a long-term trend during 1960 to 1998.
Over this period the tropical easterlies and the tropical jet stream have
weakened with time.