Institute of Natural and Technical Systems, Russian Federation, Sevastopol, Lenin St., 28
In this article, we consider an updated technique for determination of coastal upwelling indices using satellite maps of the sea surface temperature and the near-surface wind. The technique is considered on the example of seasonal variability of the Benguela upwelling. As it is known, one of the main indexes of upwelling is the thermal upwelling index TUI. To calculate TUI, it is necessary to select an area in the sea located at a certain distance from the upwelling area. The article shows that a remote (offshore) area should be selected according to certain rules in order to minimize errors in the calculation of TUI. The main difference between this method and existing ones is that the calculation of upwelling parameters and other environmental characteristics (near-surface wind, sea level anomalies, etc.) is made on monthly climate masks. The method of determining the climate masks is described in detail.
The proposed method was tested in calculations of seasonal variability for the entire region of the Benguela upwelling. The monthly climatic values of the thermal upwelling indices were calculated, which showed the maximum upwelling intensity in May-June, and the minimum one in November. The monthly climatic values of the wind indexes of upwelling were also calculated: the Ekman index of upwelling or the Ekman transfer and the Ekman pumping. The upwelling indices were calculated within the monthly climate masks and then were normalized by dividing by the number of values in the maximum mask. Thus, the areas of the upwelling waters, various in different climatic months, were taken into account. Based on the results of this work, it was concluded that the proposed refined methodology for determining the indices of coastal upwelling from satellite data makes it possible to more accurately calculate the upwelling boundaries in each climatic month and, therefore, to more accurately calculate its indices and other parameters.
Keywords: thermal upwelling index, Ekman transport, Ekman pump, sea surface temperature, nearsurface wind.
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