Variability of seasonal and annual precipitation in Slovenia and its correlation with large-scale atmospheric circulation

This paper examines temporal and spatial variability and trends of annual and seasonal precipitation in Slovenia and their relationship with three atmospheric circulation patterns represented by their indices: North Atlantic Oscillation index (NAOi), Mediterranean Oscillation index (MOi) and Western Mediterranean Oscillation index (WeMOi). Data from 45 precipitation stations were used for the period 1963-2012. Mean annual precipitation varies from 736 mm in eastern Slovenia to 2,518 mm in northwestern Slovenia. A significant annual precipitation decrease (from -3% to -6% per decade) is observed in western Slovenia. Significant negative trends are observed in southwestern Slovenia in summer (from -4% to -10% per decade) and near the Adriatic coast in spring (from -6% to -10% per decade). Non-significant negative and positive trends are observed in winter and autumn, respectively. Results indicate significant correlations between winter precipitation and MOi (from -0.3 to -0.7), NAOi (from -0.3 to -0.6) and WeMOi (from 0.3 to 0.6). Significant WeMOi influence is observed in spring and autumn, while NAOi and MOi influence has not been detected. Annual precipitation and WeMOi are significantly correlated in central and eastern Slovenia, while significant NAOi and MOi influence is observed in western Slovenia (with the larger area covered by MOi influence).