Abstract: Based on the daily maximum wind speed and wind direction data of coastal zone weather stations in Liaoning province from 1971 to 2015,the temporal and spatial distribution characteristics of gale days and its variation were analyzed.The results show that the number of gale days is highest in spring and followed by winter and summer.The monthly variation of the number of gale days is a bimodal type in the northern part of Bohai Sea and Bohai Strait with a peak value in April.The northerly and southerly winds dominate in the coastal zone and the east and west winds occur infrequently.The number of gale days in most of weather stations of coastal zone shows a decreasing trend except the Gai county.The decreasing trend in the Bohai strait is most significant with a rate of 19.3 d/10 a,followed by the northern part of the Bohai Sea.The decrease rate in the northern part of the Yellow Sea is relatively smaller.In addition,the number of gale days in the northern part of Bohai Sea and the Bohai Strait show a main cycle of about 7 years,and a decreasing climate abrupt change occurs in the 1980s.Besides an 11-year cycle occurs in the northern part of the Yellow Sea and an abrupt decreasing appears after the 1970s.There are three high-value centers including Lüshunkou-Dalian,Changhai and Jinzhou-Panshan and three low-value centers such as Donggang,Suizhong and Pulandian area for the averaged annual gale days in the coastal zone of Liaoning province in recent 45 years.The high and low incidence areas demonstrate a cross-distribution.The zonal index enhancement leads to a weakening of meridional circulation,which is not favorable to the exchange between cold and warm air.The Asia polar Vortex Area Index and the Northern Hemisphere Polar Vortex Area Index decrease significantly and the polar vortex central position is northward propelling,implying that the intensity and frequency of the cold air activity are reducing.The weakening Siberia high intensity cuts down the pressure gradient in the east-west direction.As a result,the decreasing frequencies of cold wave and strong cold air and the daily range of temperature may be the important reason for decreasing the number of gale days in the coastal zone.

Key words: Coastal zone, Gale days, Abrupt change, Cycle