SEASONAL AND INTERANNUAL VARIABILITY OF COASTAL UPWELLING ALONG NORTHWEST AFRICA AND PORTUGAL FROM 1981 TO 1991
SEASONAL AND INTERANNUAL VARIABILITY OF COASTAL UPWELLING ALONG NORTHWEST AFRICA AND PORTUGAL FROM 1981 TO 1991
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DOI：
10.1029/94jc00814
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发表时间：
1994-07-15
影响因子：
3.6
通讯作者：
VANCAMP, L
中科院分区：
文献类型：
--
作者：
NYKJAER, L;VANCAMP, L
利用1981 ~ 1991年的海表温度（SST）和风场遥感资料，研究了非洲西北部上升流区海岸上升流的季节和年际变化。从国家海洋和大气管理局全球区域覆盖数据中产生了大约3400幅单独的SST图像，并进行了重新采样，形成了一个连贯的无云数据集。从卫星资料中导出了一个定义为纬向温差的SST上升流指数，它是纬度和时间的函数。来自欧洲中期天气预报中心的风数据已被用来确定第二个上升流指数，该指数计算为垂直于海岸的埃克曼输送的分数。这两个独立的指数进行了比较，与以前公布的数据的季节性变化，并已检查年际变化。一般来说，这两个上升流指数表明，已知的季节性变化，存在以南的20度N和以北的25度N和几乎永久的上升流之间的20度N和25度N。在葡萄牙和Cape Ghir，最大风速和最大纬向温差分别为2个月和3个月，而在大多数其他地点的指数在时间上相关性很好。上升流是季节性的年际变化更大的那些地区相比，上升流是占主导地位的全年。最强的年际变化被发现南部的20度N的上升流是特别弱的期间，从1982年底到1984年初，恰逢异常强烈的1982/1983年厄尔尼诺在太平洋。
The seasonal and interannual variability of coastal upwelling in the northwest African upwelling area for the period from 1981 to 1991 has been investigated using remote sensing data of sea surface temperature (SST) and wind data. Approximately 3400 individual SST images have been generated from National Oceanographic and Atmospheric Administration Global Area Coverage data and resampled to form a coherent cloud-free data set. From the satellite data set an SST upwelling index defined as the zonal temperature difference has been derived as a function of latitude and time. Wind data from the European Centre for Medium-Range Weather Forecasts have been used to determine a second upwelling index calculated as the fraction of the Ekman transport perpendicular to the coast. The two independent indices have been compared with previously published data of seasonal variability and have been examined for interannual variabilities. In general the two upwelling indices demonstrate the known seasonal variability which exists south of 20-degrees-N and north of 25-degrees-N and the almost permanent upwelling between 20-degrees-N and 25-degrees-N. Off Portugal and Cape Ghir, there are temporal shifts between the maximum winds and the maximum zonal temperature differences of 2 and 3 months, respectively, while at most other locations the indices are temporally well correlated. Interannual variabilities are greater where upwelling is seasonal compared to those regions where upwelling is dominant throughout the year. The strongest interannual variabilities are found south of 20-degrees-N where upwelling was particularly weak during the period from the end of 1982 to the beginning of 1984, coinciding with the exceptionally strong 1982/1983 El Nino in the Pacific Ocean.