Abstract

The issue of long-term tendencies in the sea surface temperature (SST) in the Benguela upwelling region and their causes is examined using the daily satellite data of the SST for 1985–2017 and the near-surface wind for 1988–2017. It is shown that in the Benguela upwelling region there has been a significant intensification of offshore winds in the last 20 years. This is accompanied by a decrease in the thermal upwelling index (taking into account the sign of the index or an increase in its absolute values) in the southern part of the Benguela upwelling, but it practically does not influence this indicator in its northern part. The probable cause for this difference is the change in the wind-field structure, which results in opposite trends in the magnitude of the wind stress curl in different parts of the Benguela upwelling. In the southern part of the Benguela upwelling, both the coastal upwelling and the vertical velocities due to the vorticity of the near-water wind intensify, while in its northern part the corresponding trends have opposite signs. This leads to a partial compensation of these two effects in the northern part of the Benguela upwelling. The cause for the change in the wind-field structure is the displacement of the center of the Subtropical High to the southeast and the concomitant reversal of the near-surface wind vectors in the coastal zone.

中文翻译：

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关于本格拉上升流区海表温度的变化：第二部分。长期趋势

摘要

使用1985-2017年SST的每日卫星数据和1988-2017年的近地表风，研究了本格拉上升流地区海表温度（SST）的长期趋势及其成因。结果表明，在本格拉上升流地区，近20年来，海上风电显着加剧。这伴随着本格拉上升流南部的热上升指数降低（考虑到该指数的符号或其绝对值的增加），但实际上在北部并不影响该指标。造成这种差异的可能原因是风场结构的变化，这导致了本格拉上涌流不同部分的风应力卷曲幅度出现了相反的趋势。在Benguela上升流的南部，由于近水风的涡度，沿海上升流和垂直速度都在增强，而在北部，相应的趋势则有相反的迹象。这导致在本格拉上升流北部的这两种影响得到部分补偿。风场结构发生变化的原因是亚热带高压中心向东南方向的位移以及沿海地区近地表风向的逆转。这导致在本格拉上升流北部的这两种影响得到部分补偿。风场结构发生变化的原因是亚热带高压中心向东南方向的位移以及沿海地区近地表风向的逆转。这导致在本格拉上升流北部的这两种影响得到部分补偿。风场结构发生变化的原因是亚热带高压中心向东南方向的位移以及沿海地区近地表风向的逆转。