Future Changes in Tropical Cyclone Activity in the North Indian Ocean Projected by the New High- Resolution MRI-AGCM - Monitoring and Prediction of Tropical Cyclones in the Indian Ocean and Climate Change - page 68

This implies that future changes in thermodynamic factors are more influential
than future changes in dynamic factors in determining future changes in the
spatial pattern of TC genesis frequency.
4. Summary
The 20- and 60-km-mesh MRI-AGCMs (v3.2 and v3.1) were used to generate
ensemble simulations of the present-day (1979-2003, control) and the end of
21st century (2075-2099) climates under the IPCC A1B scenario to investigate
future changes in TC activity in the North Indian Ocean (NIO). The simulations
were conducted using three different cumulus convection schemes (the
Yoshimura scheme, YS; the Kain-Fritsch scheme, KF; and the Arakawa-
Schubert scheme, AS). Future SSTs were prescribed either as the ensemble
mean of 18 CMIP3 models or as one of three different SST spatial patterns
determined by a cluster analysis of the CMIP3 models.
All ensemble simulations project insignificant future changes in TC genesis
number in the NIO. However, all experiments tend to project future increase
(decrease) in TC frequency in the Arabian Sea (Bay of Bengal). An analysis of
TC frequency is performed in order to clarify the factor responsible for the
changes in TC frequency. It turned out that TC genesis factor is of the primary
importance for the changes in TC frequency.
Changes in dynamical and thermodynamic large-scale parameters were
investigated to better identify the factors responsible for the projected future
changes in TC genesis frequency. It turned out that thermodynamic factors,
such as SST anomaly, relative humidity at 700 hPa, and the Maximum Potential
Intensity, appear to influence projected future changes in TC genesis. However,
dynamical parameters do not appear to be a major factor. These thermodynamic
parameters tend to depend on the prescribed SST spatial pattern. These results
suggest that uncertainties in the degree of projected future change in TC genesis
number and frequency are more attributable to difference in SST spatial patterns.
Additional SST ensemble experiments may be needed to reduce these
uncertainties.
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