Spatial and Temporal Variation Characteristics and Potential Risk Analysis of Tropical Cyclone Activities in the Northwest Pacific Ocean under the Background of Global Warming
Based on the tropical cyclone data of the United States Joint Typhoon Center,we discuss the temporal and spatial characteristics of the changes of tropical cyclone(TC) activities in the Northwest Pacific during the period of 1951 - 2015 under the background of global warming ed,and the potential risks to China were analyzed. The conclusion is as follows: ① The trend of long-term changes in the frequency of tropical cyclones(dotted line) from 1951 to 2015 has slightly increased,but it has not passed the significant level test of 0. 05. The frequency of tropical cyclones in the western Pacific Ocean mutated around 1950,and only in the early 1960s and early 1970s, and in the late 1990s and early 2000s,the increasing trend passed a significant level test of 0. 05. The long-term change trend of Super typhoon frequency from 1951 to 2015 did not change significantly. ② From the early 1951' s to the late 1950s,the annual maximum intensity and average annual strength of tropical cyclones in the Northwest Pacific showed a short-term strengthening trend,followed by a long-term weakening trend. Overall,the annual maximum intensity and annual average intensity of tropical cyclones in the Northwest Pacific show a significant downward trend. The average strength mutated around 1972,indicating that the average strength decreased significantly after 1972. The maximum intensity mutated around 1968,indicating that the maximum intensity decreased significantly after 1968. ③ In terms of the maximum intensity(maturity) stage of tropical cyclones,the path frequency, and the spatial distribution of the linear trend of observed intensity,the positions where the linear changes are rising are all close to the East Asian continent. This also means that the intensity of tropical cyclone activity in the Northwest Pacific is weakening to some extent,but the frequency and intensity of landing are very likely to increase. That is,the potential threat of tropical cyclones in the Northwest Pacific will further increase throughout the East Asian continent. ④ This result is most likely due to the increase in the latitude temperature gradient in the Western Pacific and Middle East Pacific caused by global warming,resulting in the strengthening of the Walker circulation. The strengthening of the Walker circulation can enhance the vertical shear and relative vorticity of the tropical Pacific Northwest wind. Change,This affects the space-time changes of TC activities in the Northwest Pacific.