How ENSO impacts precipitation in southwest central Asia

A linkage between ENSO and the hydroclimatic variability of the southwest central Asia region (SWCA) is established through observational analysis of precipitation, moisture flux and sea level pressure data, with further support from an atmospheric model of intermediate complexity. Enhanced precipitation in SWCA during warm ENSO events results from an anomalous southwesterly moisture flux coming from the Arabian Sea and tropical Africa, which is generated along the northwestern flank of the high pressure anomaly over the Indian and western Pacific Oceans, part of the canonical ENSO sea-saw pressure anomalies. The ENSO impact on SWCA precipitation is found to be greatest in the transition seasons of autumn and spring, but the dynamical impact on pressure and circulation persists throughout the year. This connection was particularly strong in recent decades. Model sensitivity experiments further show that this is driven primarily by tropical Pacific SST anomalies and associated large-scale sea-level pressure changes, while the Indian Ocean SST has opposite effects.