Characteristics of Wind Direction and Speed at Yongxing Island,Sansha from 1958 to 2020

WANG Guozhang; SUN Wei

doi:10.3969/j.issn.1007-6190.2025.02.009

Abstract：To provide reference for maritime navigation support services in the Xisha area,this paper analyzed the variation characteristics of wind direction and speed for Yongxing Island,Sansha from 1958 to 2020 and their causes using the methods of linear tendency analysis,Ensemble Empirical Mode Decomposi-tion(EEMD),Buishand Range Test,Pettitt Test,Standard Normal Homogeneity Test(SNHT)and Mann-Kendall abruptness test.The results are shown as follows.On Yongxing Island,the annual wind directions were mainly NE and NNE and the annual average wind speed was 4.5 m/s.The wind was relatively strong when it was from dominant directions.The wind speed was unimodal in the diurnal range and followed a W-shaped pattern in the monthly range.Seasonal dominant wind directions differed.Maximum wind speed occurred most frequently in July on the island,with WSW and SW being two main directions.For the years of interest,both the annual average wind speed and seasonal wind speed tended to decrease.The quasi-3a interannual and quasi-21a interdecadal variations were the main periods of variation in the annual average wind speed of the island.The seasonal wind speed varied mainly at the quasi-3a period.An abrupt change point took place in 1983 for the annual average wind speed and in 1983,1979,1981,and 1981 for the sea-sonal average wind speed of spring,summer,autumn,and winter respectively.The change of wind speed on the island was caused by the rise of temperature,rather than the change of wind speed in the low level of the troposphere.