Using 20 years of AVHRR data to assess the impact of the North Atlantic Oscillation on European vegetation

We use Normalized Difference Vegetation Index (NDVI) retrieved between 1982 and 2001 from the AVHRR instrument. The year-to-year variations of vegetation greenness in Europe were estimated and related the North Atlantic Oscillation NAO. Here, we intend to show the sequence of intermediate relevant physical mechanisms responsible for the changes induced in vegetation by the NAO. Therefore, upper level atmospheric circulation and surface climatic impacts were assessed by computing maps of correlation coefficient between NAO and a number of suitable meteorological variables. The most relevant results observed are obtained for the winter-spring seasons, where the positive phase of winter NAO signal is associated with positive temperature anomalies throughout most of northern Europe while it is associated with negative precipitation anomalies in the western Mediterranean. Naturally, these conditions favor (hinder) vegetation growth above (below) normal green vegetation cover conditions over large regions of northern Europe (Iberia and Northern Africa).