Decadal changes in the wind forcing over the North Sea
Decadal changes in the wind forcing over the North Sea
复制标题
北海风力的年代际变化
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
C. Schrum
中科院分区：
文献类型：
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作者：
F. Siegismund;C. Schrum
利用NCEP/NCAR再分析1958~1997年40年的资料，得到了北海的风场统计资料。这一分析包括考虑月平均风速和角分布的年代际变化。引入了风密度函数，它结合了出现频率和给定方向上的平均风速。北海被细分为3个区。分析了两个季节(10月至1月和2月至3月)3个地区风密度函数的变化。近40年来，北海年平均风速呈上升趋势，上升幅度约为10%，主要限于10~3月份。10~1月，整个北海地区近30年来西南风向较1958~1967年有所增强。从1988年到1997年的最后十年是突出的：典型的冬季风速高和西南风盛行的持续时间从10月延长到1月，在前30年中一直持续到2月和3月。近十年来，所研究的两个海子的风密度函数和3个扇区的风密度函数都是相似的。在前30年中，北海北部59°N以北的南风方向增强，这种趋势在近10年来被打破，整个北海地区的西南风方向占主导地位。
Using data from the NCEP/NCAR reanalysis for the 40 yr period from 1958 to 1997, a wind statistic for the North Sea is derived. This analysis includes consideration of the monthly mean wind speed and decadal variability in angular distribution. The wind density function is introduced, which combines frequency of occurence and mean wind speed for a given direction. The North Sea is subdivided into 3 sectors. Changes in the wind density function for the 3 regions are analysed for 2 seasons, October to January and February to March. The annual mean wind speed for the North Sea shows a rising trend of ~10% during the last 40 yr, mainly restricted to the period from October to March. For October to January, west-southwesterly wind directions are enhanced in the last 3 decades compared to the period from 1958 to 1967 for the whole North Sea area. The last decade from 1988 to 1997 is outstanding: The duration of typical winter wind conditions, with high wind speeds and the prevalence of west-southwesterly winds, is extended from October to January in the first 3 decades towards February and March in the last one. The wind density functions for both sea- sons investigated and all of the 3 sectors resemble each other in the last decade. In the first 3 decades an enhancement of southerly wind directions is found in the northern part of the North Sea, north- ward of 59° N. This trend is broken in the last decade when west-southwesterly directions for the whole North Sea area predominate.