Abstract:

According to the observed daily maximum wind speed data of 670 stations over the mainland of China during 1980-2014, tropical cyclone high winds (TCHW) (above the 6th grade, wind speed at least 10.8 m/s) are partitioned by the method of improved Objective Synoptic Analysis Technique (OSAT). After defining tropical cyclone extreme winds (TCEW), changes of TCHW and TCEW over China are studied in this study. Results are as follows. For geographical distribution, annual mean TCHW days and its proportion decrease quickly from the coastline to inland, with proportion values of 30%-70% over Hainan, coastal provinces in South China and Southeast China and southern Jiangsu. Meanwhile, TCEW mainly appear in coastal provinces (except Tianjin and Hebei provinces), especially over coastal areas in East China and South China with proportion values reaching 100% at locations. For seasonal variation, average frequency of TCEW is more than monsoon’s extreme winds from July to September. For the whole China mainland, when wind speed threshold change from the minimum threshold (11.5 m/s) to the 12th grade (wind speed at least 32.7 m/s), the occupation of TCEW increases sharply from 12% to 77%. During 1980-2014, days of TCHW and TCEW both decrease significantly whereas average intensity of TCEW increases, which may be associated with the significant downward trend of influencing TC frequencies for TCEW and the significant upward trend of average intensity of influencing TC for TCEW during TC life and the impacting period.

Key words: tropical cyclone high winds, tropical cyclone extreme winds, Objective Synoptic Analysis Technique (OSAT)