Dominant patterns of AVHRR NDVI interannual variability over the Sahel and linkages with key climate signals (1982=2003)

The spatio- temporal evolution of Sahelian vegetation is analyzed using the Normalized Difference Vegetation Index ( NDVI) obtained from the NOAA/ AVHRR sensor ( 1982 2003). Dominant patterns are identified using rotated EOFs. While the first four modes are associated with specific biogeoclimatic conditions in space, significant time scales are detected using a multi- tapers method. Three interannual time scales ( similar to 6.2-, 4.5- and 3.6- year) are present in the first and third NDVI modes over the western Sahel. A quasi- biennial time scale ( similar to 2.6- year) is present in second and fourth NDVI modes over the northeast Sahel. During summer, significant lagged correlations are found between the NDVI second ( 9- month lag) and third ( 10- month lag) modes, the meridional Atlantic Sea Surface Temperature ( SST) gradient, and the zonal SST gradient in the Indian Ocean. Potential physical linkages and dynamics with known climate fluctuations are discussed. Citation: Jarlan, L., Y. M. Tourre, E. Mougin, N. Philippon, and P. Mazzega ( 2005), Dominant patterns of AVHRR NDVI interannual variability over the Sahel and linkages with key climate signals ( 1982 - 2003), Geophys. Res. Lett., 32, L04701, doi: 10.1029/ 2004GL021841.