Links between Arctic Oscillation (AO) and inter-annual variability of Iranian evapotranspiration

摘要

Understanding the responding mechanism of reference evapotranspiration (ET_O) to large-scale atmospheric circulation patterns is of particular concern in arid and semi-arid environments, where water resources scarcity constrains agriculture. This study investigates the statistical relationships between the Arctic Oscillation (AO) and the annual and seasonal mean ET_O values of 41 weather stations in Iran for 1966-2005. The connections between the AO index and annual ET_O are also examined during the extreme phases of the AO (high and low phases). Significant correlations between annual ET_O and the corresponding AO index are quite rare, and the differences between the ET_O values during the extreme AO phases and the long-term average ET_O values were found to be significant only at three out of the 41 study stations. The lag correlations indicated that the greatest positive (0.506) and negative (-0.466) correlation coefficients were found for 2-season time lag. Furthermore, the mean time lag between the start of the AO events and the observed maximum effects on ET_O at the study stations was about 1.61 seasons or 5 months.