基于ERA5的南大西洋风速和有效波高时空变化特征分析

Analysis of temporal and spatial changes of wind speed and significant wave height in the South Atlantic based on ERA5

基于1979—2019年欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)ERA5逐月平均风速、有效波高,分析了风速和有效波高的时空变化特征。利用Mann-Kendall检验法分析其年际变化和经验正交函数分析方法(Empirical Orthogonal Function,EOF)研究空间分布特征。结果表明:(1)南大西洋风向以30°S,10°W为中心逆时针旋转,风速大值区以东南信风带和西风带控制区为主,低值区以副高和低压带控制区为主。冬季风速高于其他季节,且全年风速和风向分布天气系统的季节变化有关。(2)有效波高与风速之间有很强的相关性,且二者都呈纬向环状型空间分布特征。冬季有效波高整体最大,夏季整体偏小。(3)Mann-Kendall检验结果显示风速和有效波高年际变化均呈上升趋势,风速在2006和2009年附近出现突变,有效波高于1994年前后出现突变。(4)风速EOF第一模态显示,信风带-西风带与副高带-低压带反向型分布,前者风速呈显著上升趋势,后者呈下降趋势。有效波高EOF第一模态显示:60°S以北海域有效波高变率为正位相,以南为负位相,正位相区域有效波高增大趋势显著,负位相区域有效波高减小趋势显著。

Based on the monthly average wind speed and significant wave height of the European Centre for Medium-Range Weather Forecasts(ECMWF) ERA5 from 1979 to 2019,the temporal and spatial characteristics of wind speed and significant wave height were analyzed.The Mann-Kendall test method was used to analyze its inter-annual variation and the Empirical Orthogonal Function(EOF) analysis method was used to study the spatial distribution characteristics.The results showed that:(1) The wind direction of the South Atlantic Ocean rotated counter clock wise with 30°S and 10°W as the center.The areas with high wind speed were mainly controlled by the southeast trade wind belt and the west wind belt,and the low value areas were controlled by the subtropical high and low pressure zone.The wind speed in winter was higher than other seasons,and the wind speed and wind direction distribution throughout the year were related to the seasonal changes of the weather system.(2) There was a strong correlation between wind speed and significant wave height,and both of them were distributed in a zonal ring shape.The overall significant wave height was the largest in winter and smaller in summer.(3) Mann-Kendall test results showed that the inter-annual variation of wind speed and significant wave height both showed an upward trend.The wind speed had abrupt changes around 2006 and 2009,and the significant wave was higher than around 1994 and had abrupt changes.(4) The first mode of EOF of the wind speed showed that the trade wind belt-westerly belt and the subtropical high belt-low pressure belt were distributed in the opposite pattern.The wind speed of the former showed a significant upward trend,and the latter showed a downward trend.The first modal of EOF of the significant wave height showed that the significant wave height variability in the north sea area of 60°S was the positive phase,and the south was the negative phase.The significant wave height in the positive phase region had a significant increasing trend,and the significant wave height in the negative phase region had a significant decreasing trend.