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 66

each grid box. Figure 3 shows ensemble mean projected future changes in the
spatial distributions of TCF. Locations where these changes are robust (i.e.,
the mean future change is statistically significant at the 90% confidence level
and changes in more than 12 out of 15 individual experiments are of the same
sign as the mean future change) are marked with crosses.
TCF are projected to decrease significantly and robustly in the Bay of
Bengal, and increase significantly in the Arabian Sea. Although the experiments
using KF show decrease in TCF in the Arabian Sea, most of the experiments
are robust in the spatial contrast.
An analysis of TCF suggests that the genesis factor is responsible for both
projected TCF increase in the Arabian Sea and decrease in the Bay of Bengal.
In contrast, the TC track factor is of secondary importance for the TCF changes,
indicating that the future changes in TCF are substantially caused by the future
changes in the local TC genesis frequency.
Fig. 3: Ensemble mean future changes in tropical cyclone frequency (TCF, shading)
[number/25-year]. Each panel shows the ensemble mean of (a) all experiments, and
(b-d) experiments using: (b) Yoshimura convection scheme (YS), (c) Kain-Fritsch (KF)
convection scheme, and (d) Arakawa-Schubert (AS) convection scheme. Cross marks
indicate ensemble-mean differences that are consistent among the experiments.
3.3 Mechanisms of Future Changes in TC Genesis Frequency
Several factors may possibly be associated with TC genesis frequency. A number
of previous studies have reported relationships between large-scale dynamical
and thermodynamic parameters, and variations in TC genesis. The analyzed
large-scale parameters were relative vorticity at 850 hPa ([ 850 ), relative humidity
at 700 hPa ( RH ), maximum potential intensity ( V pot ), vertical wind shear
between 200 and 850 hPa ( V s ), vertical pressure-velocity at 500 hPa (Z 500 ),
saturation deficit in the lower troposphere, atmospheric static stability (* d ),