Long-term ENSO relationship to precipitation and storm frequency over western Himalaya-Karakoram-Hindukush region during the winter season

The interannual precipitation variability over Western Himalaya-Karakoram-Hindukush (WHKH) region has a significant impact on the freshwater resources, energy and agriculture sectors. Midlatitude storms play the role of an atmospheric bridge between large-scale circulation patterns and regional precipitation distributions during the winter (December-April) season. In this study, we investigated long-term changes between El Nino Southern Oscillation (ENSO) and storm activity as well as between ENSO and for precipitation, over WHKH for the period 1950-2015. The Melbourne University Objective Cyclone Identification and Tracking Scheme is used to track the midlatitude storms. A non-linear relationship is identified between the storm track frequency and precipitation over the WHKH region. The correlation between the storm frequency and precipitation increases significantly (95%) after the 1980s and reaches a maximum value of 0.53. Furthermore, 21-year running correlations also show non-linear relationships between ENSO and WHKH's precipitation as well as for storm tracks frequency. The simultaneous correlation between storm tracks frequency (precipitation) and Nino3.4 index was insignificant 0.03 (0.25) in the earlier period from 1950 to 1979, which surged to 0.47 (0.60) in recent 30-years period from 1986 to 2015. Composites and regression analysis illustrate that ENSO modulated the midlatitude storm tracks over the WHKH region, which in turns impact more precipitation anomalies in the recent 30-years period. Moreover, Saudi King Abdulaziz University Atmospheric General Circulation Model (Saudi-KAU AGCM) also confirms the change in the relationship between ENSO and WHKH precipitation variability during the winter season between the two periods. These findings may have important implications for the seasonal rainfall predictability of the WHKH region.