A Possible Influence of Global Warming on Typhoons
Masato Sugi
Meteorological Research Institute (MRI)
Tsukuba, Japan
The influence of the global warming on tropical cyclones has been examined using a high resolution AGCM. Two ten-year integrations were performed with the JMA global model at T106 horizontal resolution. For the control experiment, the observed SST for the period 1979-1988 is prescribed, while for the 2×CO2 experiment, SST anomaly due to the global warming estimated from a coupled model transient CO2. The results of experiments show that a significant decrease in the frequency of tropical cyclones is possible in response to the greenhouse gas-induced global warming. Most significant decrease is indicated over the North Pacific. On the other hand, a considerable increase in tropical cyclone frequency is indicated for the North Atlantic. A slight increase is seen over the North Indian Ocean, while significant decrease is seen in the Southern Hemisphere, both in the Pacific and Indian oceans. As for the intensity of experiment (Tokioka et al. 1995) is added to the SST used in the control experiment optical cyclones, no significant change has been noted.
It has been found that the regional change in tropical cyclone frequency is closely related to the distribution of the SST anomaly and the change in convective activity associated with it. On the other hand, for the decrease in the global total number of tropical cyclones on doubling CO2, a weakening of tropical circulation associated with the stabilization of the atmosphere seems to be responsible for it. The weakening of tropical circulation is consistent with that the amount of increase in tropical precipitation due to the global warming is much less than the amount of increase in water vapor in the atmosphere.
