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The seasonal and interannual variability of coastal upwelling in the northwest African upwelling areas for the period from 1981 to 1991 has been investigated using remote sensing data of sea surface temperature (SST) and wind data. 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 have been used to determine a second upwelling index, calculated as the fraction of the Ekman transport perpendicular to the coast. In general, the two upwelling indices demonstrate the known season variability which exists south of 20 N and north of 25 N and the almost permanent upwelling between 20 N and 25 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. Internannual variabilities are greater where upwelling is seasonal compared to those regions where upwelling is dominant throughout the year.

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Authors: NYKJAER L, JRC Ispra (IT);VAN CAMP L, JRC Ispra (IT)
Bibliographic Reference: Article: Journal of Geophysical Research, Vol. 99 (1994) No. C7, pp. 14197-14207
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