Mechanism of the Indian Ocean Tropical Cyclone Frequency Changes due to Global Warming - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 39

Mechanism of the Indian Ocean
Tropical Cyclone Frequency Changes
due to Global Warming
Masato Sugi*, Hiroyuki Murakami and Jun Yoshimura 1
Japan Agency for Marine-Earth Science and
Technology, Yokohama, Japan
1 Meteorological Research Institute, Tsukuba, Japan
*e-mail: [e-mail]
1. Introduction
Recent high resolution models consistently show that the global tropical cyclone
(TC) frequency will decrease in the future due to global warming (Knutson et
al., 2010). Sugi et al. (2002) pointed out that the reduction of global TC
frequency in the future is closely related to the weakening of upward mass flux
in the tropics. Recently, Sugi and Yoshimura (2012) found a clear decreasing
trend of global TC frequency throughout the 228-year simulation for the period
1872-2099, which is also closely related to a decreasing trend of upward mass
flux.
In contrast to the global TC frequency change, there is a very large
uncertainty in the projected regional TC frequency changes (Knutson et al.,
2010). Sugi et al. (2009) showed that one of the major sources of uncertainty
in the projection of regional TC frequency changes is the uncertainty of projected
pattern of sea surface temperature (SST) changes. In addition, it is possible
that the mechanism of TC frequency change could be different in each region.
In the present study, we further explore the possible mechanism of global and
regional TC frequency changes due to global warming based on a series of
experiments with a high resolution MRI-AGCM, with particular focus on the
TC frequency changes in the Indian Ocean.
2. Hypothesis
Based on the previous studies (Yoshimura and Sugi, 2005; Held and Zhao,
2011; Sugi et al., 2012), we can propose the following hypothesis as a