The Climate Characteristics Of Tropical Cyclone Activity In The Northwest Pacific Under The Background Of Global Warming

In this paper, the mesoscale atmospheric numerical model(MM5) is used to studies the activity of tropical cyclone in the Northwest Pacific, with a background of global warming. Two sets of simulation experiments are used in this paper, each set includes 44 cyclones cases tropical with different locations representing the tropical cyclone of present and future, respectively. For present scenarios, the National Center for Environmental Prediction (NCEP) reanalysis data averaged from 1971 to 2000 are used as initial and lateral boundary fields representing the climate in present. For future scenarios, we use the data from 2031-2060 simulated by U.S. National Oceanic and Atmospheric Administration's(NOAA) model named GFDL CM2.0 with the A2 scenarios in the fourth assessment of United Nations Intergovermental Panel(IPCC) as initial and lateral boundary fields of future climate. The A2 scenarios represent that in the 100 year between 2000 and 2100, CO2 concentration in the troposphere increased from the current 380ppm to 800ppm with the average growth rate of 4.2ppm/Year.The results show that the intensity of tropical cyclones enhanced significantly in the condition of global warming. Comparing with current climatic background, the tropical cyclones generate in the western pacific(west of 130°E) are stronger than those generate in the eastern pacific. Among the tropical cyclones of the future, those generate over 10°-15°N are strongerest mostly, those generate over 5°N are a little weaker than those above, hose generate over 20°N are the weakest. And the tropical cyclones in the future move more east and turn northeastward earlier than those present. Location of tropical cyclones in the future when they reach to maximum intesity are more south and more east than those of tropical cyclones present. Studying the relationship of tropical cyclones and sea surface temperature(SST), relative vorticity between 1000 and 500hPa(VOR), vertical wind shear between 200 and 850hPa(VWS), relative humidity with 600hPa(RHU), it can be found that the effect of SST to the intensity of tropical cyclones 24 hours later is well, that means in the areas where SST one day before is more higher, tropical cyclone is more stronger. In the area to the west of 130°E and between 10°N and 15°N tropical cyclones in the future are more stronger, what have business with SST. The effect to intensity of tropical cyclones of VOR is well in the early days, that means in the areas where VOR is more higher, tropical cyclone is more stronger. The effect of VOR to intensity of tropical cyclones is better than that to increment of tropical cyclones'intensity. There is no obvious delay in the correlation between VOR and tropical cyclones,In the area of 15°N tropical cyclones in the future are more stronger, what have business with VOR. The correlation between VWS and intensity of tropical cyclones is very well, but the effect of VWS to increment of tropical cyclones' intensity is worse than than to intensity of tropical cyclones. In the area to the west of 145°E tropical cyclones in the future are more stronger, what have business with VWS. The effect of RHU to intensity and increment of intensity of tropical cyclones under other vars'effect is a little bit better than that without other vars'effect. Overall, there is amostly no correlation between RHU and tropical cyclones.It can be well expained that the distribution of intensity of tropical cylones in the two Climatic background be according to the correlation between the variables and intensity and increment of intensity of tropical cyclones above.