| dc.description.abstract | This study uses the Max Plank Institute (MPI) coupled model (ECHAM4/OPYC3) to simulated the IPCC A2 and B2 global warming scenarios. We discuss the total number, lifetime, intensity, track variation of tropical cyclones under different climate scenarios in the Northwest Pacific Ocean.
According to the results, we find that when greenhouse gases increase, there are several changes occured in the Northwest Pacific Ocean. (1) Sea surface temperatures increase. (2) Subtropical high ridge extends westward. (3) Relative humidities of lower and middle troposphere increase. (4) Temperatures increase in troposphere. (5) Walker circulation weakens. (6) Monsoon trough weakens in the South China Sea and Philippines region, and vertical wind shear weakens over the South China Sea. In addition, comparing the difference between A2 and B2 scenarios, we find that the changes of climate trend in B2 are almost the same as A2, but the amplitude in A2 is larger.
Furthermore, we find that the total number of tropical cyclones decrease in the Western North Pacific under the A2 and B2 simulations. This reduction is associated with the increase of sea surface and air temperatures. The weakening of Walker circulation will increase water vapor in atmosphere. These processes will make atmosphere warmer and more moisture. This in turn increases the static stability of the troposphere. The process restrict the convection activity and hence reduce the total number of tropical cyclones.
In addition, the northeastern recurving tracks of tropical cyclones shift southwesterly. This attributes to westward extend of the subtropical high ridge and weakening of westerly steering flow in middle latitude.
Finally, the lifetime and intensity variation of tropical cyclones under the A2 and B2 climate change simulations may be affected by the differences in method, model and atmosphere interannual variability. In these part of tropical cyclone characters, we still need further study to prove. | en_US |