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

Abstract:

Understanding the responding mechanism of reference evapotranspiration (ET<inf>o</inf>) 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<inf>o</inf> values of 41 weather stations in Iran for 1966-2005. The connections between the AO index and annual ET<inf>o</inf> are also examined during the extreme phases of the AO (high and low phases). Significant correlations between annual ET<inf>o</inf> and the corresponding AO index are quite rare, and the differences between the ET<inf>o</inf> values during the extreme AO phases and the long-term average ET<inf>o</inf> 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<inf>o</inf> at the study stations was about 1.61 seasons or 5 months.