The Impacts of the NAO on the Vegetation Activity in Iberia

Abstract

The present study analyses the relation between North Atlantic Oscillation (NAO) and satellite-based measures of vegetation dynamics (as obtained using Normalized Difference Vegetation Index, NDVI), carbon absorption by living plants (obtained by Net Primary Production, NPP estimates) over Iberian Peninsula and wheat yield in Portugal. There is a strong evidence that positive (negative) values of winter NAO induce low (high) vegetation activity in the following spring and summer seasons. Consequently, significant correlations patterns between NAO and NPP were also obtained, identifying a negative impact in spring and summer over southern Iberia. These features are mainly associated with the impact of NAO on winter precipitation, together with the strong dependence of the spring and summer vegetation activity on water availability during the previous winter. The different role played by NAO along the vegetative cycle of wheat yield in Portugal is also assessed and results obtained suggest using spring NDVI together with NAO in April and June to build up a simple model of wheat yield in Portugal. Results reveal to be satisfactory and are expect to be useful to estimate crop production and to perform agricultural monitoring.