Geoscience Reference
In-Depth Information
Tropical Cyclone Activity over the
Indian Ocean in the Warmer Climate
A.A. Deo* and D.W. Ganer
Indian Institute of Tropical Meteorology, Pune - 411008
*e-mail: aad@tropmet.res.in
1. Introduction
Research efforts focussed on assessing the potential for changes in tropical
cyclone activity in the greenhouse-warmed climate have progressed since the
IPCC (Inter-Governmental Panel for Climate Change) assessment in 1996.
Vulnerability to tropical cyclones (TCs) becoming more pronounced due to
the fastest population growth in tropical coastal regions makes it practically
important to explore possible changes in tropical cyclone activity due to global
warming.
It is an established fact that sea surface temperature (SST) >26 ° C is a
requirement for TC formation in the current climate (Gray, 1968; Lighthill et
al., 1994). As the SSTs become warmer, certain tropical ocean basins may face
an increasing number of and/or more intense tropical cyclones (Chu and Clark,
1999). Several studies have pointed out that global and tropical atmospheric
temperatures near surface and aloft are increasing (Parker et al., 2004; Jones
and Moberg, 2003; Santer et al., 2005; Smith and Reynolds, 2005). Tropical
ocean SSTs have been increased by approximately 0.5 ° C between 1970 and
2004 (Elsner and Kocher, 2000). TCs form only over warm oceans from which
they gain energy (Anthes, 1982; Emanuel, 1987; Holland, 1997). Hence we
could expect that a warmer and moister environment would have an enhanced
overall cyclone activity (Anthes, et al., 2006). Emanuel (2005a, 2005b), Webster
et al. (2005), Hoyos et al. (2006), and Holland and Webster (2007) have
suggested an increase in the frequency of occurrence of intense TCs in the past
30 years and related this to a concomitant increase in SST which may or may
not be caused by global warming. In this study the TC activity over Indian
Ocean is investigated by examining the parameters like storm frequency, storm
days, cyclogenesis etc., in relation to other ocean basins.
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