Statistical Studies On Warm-warding Movement Of Landfalling Super Typhoon Over China

With the Yearbook of Typhoon and Yearbook of Tropical Cyclone data, this paper selects super typhoons(super TYs) which made landfall on China mainland (not including Taiwan) from 1960 to 2009, and performs statistical analyses of the change characteristics of their landing number, landing strength and landing location. The results indicate that the numer of super TYs landed in south of 24°N over China decreased gradually from the 1980s while increased significantly in north of 24°N, and the landfalling locations have a northward trend from 1980s to 2000s. This paper uses the monthly average sea surface temperature (SST) from the NOAA ERSST (Extended Reconstructed Sea Surface Temperature) achive as well as the daily average land surface temperature (Ts) and soil-air tempertature differences (Ts-Ta) data which include 753 stations over China from the CMA(China meteorological administration) achive from 1960s to 2009 to study the relationship between the thermal condition changes of inshore coastal areas as well as the landing areas before landfalling and the landfalling super TYs warm-warding movement and to figure out the reason of northward trend.Inshore coastal SST of China (20°N～36°N) is in a trend of rising, same with the trend of annual average landing latidude of super TYs from 1960 to 2009. Moreover, the rising trend in north is greater than in south. The SST anomaly (SST of the landing day minus SST of the landing month average for 50 years) of tropical cyclones (including super TYs, severe typhoons, typhoons, severe tropical storms and tropical storms) and the landing latitude have significant positive correlation:the waremer the SST, the higher the landing latitude. The inshore SST anomaly has a northward trend; the concentrated track area of super TYs is the warmer SST anomaly zone in 2000s.As to Ts, the warmest areas of composite Ts two days before landfalling of 12 super TYs in 1980s and 10 super TYs in 2000s are just the most concentrated landfalling area of these super TYs, besides, the landfalling area of other 3 decades are also the warmer Ts areas. Ts are increasing higher in high latitude areas than in low latitude areas.The trendline of annual average landing latidude is in parallel with the trendline of the corresponding latitude of the maximum Ts anomaly. In order to study the deviation between landing location and Ts warmer zone, this paper performs a further statistical analysis on the relationship between the tracks of the super TYs and the corresponding Ts at the time of two days before landing. The results show that Ts is an important factor which affects super TYs moving. Five individual super TYs are analysed, and find that they did not follow the environment steering flow at the sounthern edge of the sub-tropical high, instead they cross over the steering flow and move toward the warmer Ts zone, the average Ts (from 3 day before landing to 1 day before landing) of landing location are the warmest Ts zone of coast of china.As to Ts-Ta, it is similar to Ts. The warmest areas of composite Ts-Ta two days before landfalling of 12 super TYs in 1980s and 10 super TYs in 2000s are just the most concentrated landfalling areas of these super TYs, except 1970s, the landfalling areas of 1960s and 1990s are also the warmer Ts-Ta areas. The trendline of annual average landing latidude correspond better with the trendline of the corresponding latitude of the maximum Ts-Ta anomaly than with the trendline of the corresponding latitude of the maximum Ts-Ta which indicates that there is certain relationship between the heating Ts-Ta area and the super TYs movement. The statistical analysis on deviation between landing location and Ts-Ta warmer zone show that Ts-Ta is an important factor affect super TYs moving. Four individual super TYs are analysed, and find that they did not follow the environment steering flow at the sounthern edge of the sub-tropical high, instead they cross over the steering flow and move toward the warmer Ts-Ta zone, the average Ts-Ta (from 3 day before landing to 1 day before landing) of landing location are the warmest Ts-Ta zone (greater than 6℃)on the coast of China.Based on the comprehensive analysis of the thermal characteristics of super TYs, this paper builds a land surface warm-warding comprehensive model of super TYs.To sum up, although the conclusion of Ts, Ts-Ta and SST has certain limitations and is only a preliminary conclusion, the thermal properties of the inshore coastal sea surface and landfall surface indeed affect the movement and landing of super TYs. Taking SST, Ts and Ts-Ta in account when predict the inshore super TY movement, it will be helpful to improve the accuracy of the forecasts.