Response Analysis Of The Formation And Development Of Tropical Cyclone To ENSO Events In The SCS

As global warming and the deterioration of climate and environment worsen,tropical cyclone(TC)not only frequently occurs,but its intensity also tends to increase.The South China Sea(SCS)is not only an important transit places for TC in the Western Pacific,but also a place where TC originates(commonly known as local typhoon).The SCS transits and generates more than 10 TC per year on average.The huge waves and heavy rains caused by TC have caused serious disasters to the offshore environment,causing major safety hazards and economic losses to marine operations,transportation,coastal protection projects and marine fisheries,which have seriously affected the normal activities of China's marine and coastal economic and social activities.El Ni?o and Southern Oscillation are collectively referred to as ENSO,that is an anomaly in tropical oceans and atmospheres,with obvious cycle characteristics.ENSO not only affects the generation and development of TC,but also induces global climate anomalies,causing severe drought or freezing weather in many parts of the world.Therefore,strengthening the research on the relationship between TC evolution and ENSO events in the SCS under the background of global warming climate can not only provide an important scientific basis for the prediction and disaster prevention and reduction of TC in China,but also provide important support for marine fisheries and engineering activities and marine shipping safety.First,this paper uses multi-source remote sensing and reanalysis data to develop the impact of the 2014 SCS super typhoon Rammasun on the dynamic environment of the South China Sea.The results show that after the typhoon passes,the depth of the SCS mixed layer is increased by an average of 19.3%.The sea surface temperature(SST)cool has a 3d delay effect.The obvious “right” strengthening relative to the typhoon path.The heavy rainfall caused by the typhoon has a significant “left deviation”.In-depth analysis shows that typhoon-induced strong Ekman pumping velocity(EPV)and upper seawater mixing are the main reasons for the continuous decline in upper sea temperature.Secondly,the China Meteorological Administration's TC data from 1950 to 2017 for the past 70 years were used to systematically analyze the frequency,occurrence,maximum wind speed and movement of tropical typhoon in the SCS in normal years,El Ni?o years and La Ni?a years.The seasonal changes of key factors such as speed explore the difference between the local and non-local(transit)TC in the SCS in response to ENSO and normal years.The study found that compared with transit SCS TC,local TC showed significant differences in frequency,movement speed and germination time.On the one hand,local TC in the SCS generates an average of 5-6annually,while non-local TC generates 6-7 annually.On the other hand,the local TC in the SCS moves slowly,mainly concentrated on 2.6-4 m/s,while the average non-local TC can reach 4.1-5.5 m/s.In addition,the occurrence time of local TC in the SCS in summer and autumn mostly occurs at 00 o'clock at night,with a corresponding probability of 39%.The transit time of non-local TC has no such characteristics.In addition,it reveals the spatiotemporal characteristics of the TC of the SCS Bureau in the ENSO and normal years on the place of occurrence and transit path.In the normal year and El Ni?o year,the TC of the SCS was relatively concentrated north of 12°N,mainly located in the southwest of Luzon,and relatively scattered in the south of 12°N.The summer birthplace of El Ni?o year was relatively normal It moved 3 latitudes south,and for La Ni?a it moved 2 latitudes south.The local TC in the SCS are in the same direction in the normal year,El Ni?o year and La Ni?a year,but the El Ni?o year path moves northward by 2 latitudes relative to the normal year,and moves northward by one latitude relative to La Ni?a,at the same time,the fastest movement towards summer and the longest in autumn.Finally,the difference between the frequency and maximum wind speed of ENSO and normal years in local and non-local TC in the SCS was discussed and analyzed.The results show that in ENSO years,the local TC in the SCS have a frequency of 5 and a transit of 6;There is 6 TC occurrences and 7 transit.The maximum wind speed is in ENSO years.The SCS local TC is located in the northeast of the Xisha Islands and the transit TC is located in the southwest of the Xisha Islands.In normal years,the maximum wind speed of the SCS and the transit TC is located in southern Taiwan.The local and non-local TC in the SCS are mainly concentrated in49-96 h during normal years and ENSO years.