Long-term drought severity variations in Morocco

Abstract

Cedrus atlantica ring width data are used to reconstruct long-term changes in the Palmer Drought Severity Index (PDSI) over the past 953 years in Morocco, NW Africa. The reconstruction captures the dry conditions since the 1980s well and places this extreme period within a millennium-long context. PDSI values were above average for most of the 1450-1980 period, which let recent drought appear exceptional. However, our results also indicate that this pluvial episode of the past millennium was preceded by generally drier conditions back to 1049. Comparison of PDSI estimates with large-scale pressure field reconstructions revealed steady synoptic patterns for drought conditions over the past 350 years. The long-term changes from initially dry to pluvial to recent dry conditions are similar to PDSI trends reported from N America, and we suggest that they are related to long-term temperature changes, potentially teleconnected with ENSO variability and forced by solar irradiance changes. Copyright 2007 by the American Geophysical Union.