Caractérisation spatio-temporelle de la production primaire dans la côte Nord-Ouest Africaine par Imageries Satellitaires MODISA

Fourteen years of MODIS Aqua (MODISA) ocean color data are used to characterize the spatial and temporal variability of primary production from 2002 to 2015 in seasonal and interannual timescales along the northwest African coast (between 15°N and 36°N). The ocean color data are implemented into mathematical models in order to compare between their different products. Five regions with different behaviors are identified: the area between 32°N-36°N is characterized by a strong seasonality of productivity and upwelling activity. The region between 28°N and 32°N with high productivity in comparison with the first zone accompanied by presence of chlorophyll filaments in coastal zone near Cape Ghir (31°N) and Cape Juby (28°N). The area between 25°N and 28°N shows an ascending primary production activity supported by the permanent aspect of the activity of upwelling in this area. Then, the area between 21°N-25°N, which is disturbed, is characterized by intense production in Cap Blanc (21°N). Finally, the area south of 21°N, where we notice that primary production is mostly abundant in winter season coinciding with the upwelling activity (November to April). VGPM by Behrenfeld and Falkowski in 1997 with backscattering coefficient Kd490, seems to be the most appropriate model for our region of interest. This dynamic is interpreted in regards of remotely sensed chlorophyll, radiation, and coastal upwelling index. Several attempts to correlate between in-situ measurements and satellite observations have been conducted to output a corrected equation that allows us to establish a regional model. Corrected VGPM (Kd) Model indicate a more refined relation with CUI, but on smaller scale, the suitable production model change according to upwelling zone. At interannual timescale, the models show a similar pattern of temporal evolution but with significant seasonal and spatial differences. The dynamics of biomass and primary production study and its relationship with the CUI provides an interesting framework for future studies in NWA region.