Ocean surface temperature
affects south Asian monsoon
In the Indian Ocean, the monsoon winds
move northeast, shedding rain across India and Southeast
Asia. New research by NASA indicates that fluctuations
in ocean surface temperature may affect monsoon conditions.
A monsoon is a major atmospheric circulation,
with seasonal contra-flows, which determines rainfall
patterns.
The atmospheric circulations caused
by the heating and cooling of land and ocean are responsible
for the way in which monsoons develop.
Among the most renowned of these is
the monsoon that develops from India through to South
East Asia in a characteristic pattern during June to
September. In July, the monsoon is interrupted, and
then re-starts its path.
Why the interruption? Ocean surface
temperatures are thought to play a part in a phenomenon
meteorologists call the Madden Julian Oscillation (MJO).
The MJO is known to affect atmospheric circulation,
and goes some way toward explaining weather variations
in the tropics. The oscillation is created by a very
large movement of air - eastward - which affects the
eastern Indian ocean at an altitude of 7. 5 miles (12
km) over a period of 20-70 days.
Any variations in ocean surface temperature
are now considered to affect the character of the monsoons
in the region. In this way, observations of ocean surface
temperature at any given time could provide meteorologists
with a powerful tool by which to predict the intensity
of monsoons arriving in South East Asian and Australia.
Strictly copyright copyright. ©
James A. Oliver 2003
References: American Meteorological
Society’s Journal of Climate, October 15th issue,
Volume 15, Number 20. The research was funded under
NASA’s Earth Science Enterprises Global Modelling
and Analysis Program. Support was also provided by the
Atmospheric Sciences Division of the National Science
Foundation.
Posted: 21 November 2002
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