UPWELLING AND BOUNDARY CIRCULATION OFF NORTHWEST AFRICA AS DEPICTED BY INFRARED AND VISIBLE SATELLITE-OBSERVATIONS

Satellite derived surface temperatures (AVHRR data) and chlorophyll-like pigment concentrations (CZCS data) off Northwest Africa are presented and interpreted. Sea surface temperature (SST) and pigment concentrations are used as indicators for upwelling and eastern boundary circulation. The distribution patterns of satellite derived parameters offer new insights into the upwelling system of the Northwest African coast. Typical SST images have been selected for each season (most of the SST images shown here are from 1987). Analyses of daily winds show these are related to the near-shore temperature patterns. The images of pigment concentrations are selected from the period 1980-1985. The SST images clearly show the upwelling variability along the coast of Northwest Africa. The anlyses of daily wind fields are consistent with the spatial and temporal variability of upwelling as observed in the SST images. Several mesoscale patterns which have not been described in the existing literature are noticed in the images. These apply to the long warm water trails found in the wake of the Canary Islands and to the filaments of cool coastal water extending far offshore between 32-degrees-N and 31-degrees-N. Other unusual heating patterns are found on the shelf in the shadow zone of winds and currents south of Cape Ghir and in the bay inshore of the peninsula of Rio de Oro at approximately 24-degrees-N. Finally, the special hydrographic conditions on the shallow and mostly sheltered Banc d'Arguin are confirmed in the SST images by the particular temperature patterns observed.