基于ERA5再分析数据的中国邻近海域极端波高特征分析

CHARACTERISTICS OF EXTREME WAVE HEIGHT IN CHINA’S MARGINAL SEAS BASED ON ERA5 REANALYSIS DATA

极端波浪对沿海地区基础设施有着深远的影响,了解它们的变化规律是进行海岸带风险分析和灾害预防的基础。文章基于欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasting,ECMWF)第五代再分析数据集(ECMWFreanalysisv5,ERA5),对中国邻近海域1979~2018年间极端波高展开时空特征分析,并统计了40a厄尔尼诺系数,利用广义极值分布(generalized extreme value,GEV)函数探究了近40 a厄尔尼诺现象对我国海域极端波高的影响,结果显示:统计1979~2018年整个研究区域前2%极端波浪年均值在6~10 m间浮动,且整体趋势递增,在四季趋势变化中,春夏极端波高增长趋势较秋冬高,且波动明显,在年际极端波高变化趋势中有较大波动时大多伴随着厄尔尼诺或是拉尼娜现象的发生,结合厄尔尼诺现象对GEV分布中位置参数的影响分布图和极端波高年、季节际趋势变化分布图,厄尔尼诺现象影响大的地区极端波高大多呈现增长趋势,表明厄尔尼诺现象对极端波高有较高影响。

Extreme waves have a profound impact on coastal infrastructure,and it is the basis of understanding of their variation law and prevention of disasters in coastal zones.Based on the ECMWF reanalysis the fifth generation ERA5 data set,the spatio-temporal characteristics of extreme wave heights in China’s marginal seas from 1979 to 2018 were analyzed and the 40-year El Ni?o coefficients calculated.The GEV(generalized extreme value) function was used to explore the influence of El Ni?o event on extreme wave height in the study area in recent 40 years.Results show that the annual mean value of extreme waves in the top 2% of the whole research area fluctuated between 6 m and 10 m from 1979 to 2018 and the fluctuation is increasing in overall,which is more obvious in spring and summer for having greater extreme wave height than in autumn and winter duo reasonably to the El Ni?o or La Nina works.Combining the influence of El Ni?o on the location of GEV distribution and the interannual and inter-seasonal trends of extreme wave heights,we found that most of the extreme wave heights in areas where El Ni?o has a great influence show an increasing trend,which indicates that El Ni?o has a greater impact on extreme wave heights.