PDO-driven interdecadal variability of snowfall over the Karakoram and Western Himalaya

Abstract. Our study reveals that the negative phase of the Pacific Decadal Oscillation (PDO−) leads to increased winter (DJF) snowfall in the Karakoram and Western Himalayas (KH) from 1940 to 2022. Interdecadal variations in DJF snowfall during the PDO− are attributed to deep convection and adiabatic cooling near the tropopause in both the northwest Pacific and KH region. Additionally, a wave-like pattern characterized by a trough (anomalous cyclone) north of KH and a ridge (anomalous Tibetan Plateau anticyclone) east of KH in the upper atmosphere, along the northward shift of the DJF Subtropical Jet (STJ) was observed. A strong positive correlation between DJF STJ strength and DJF snowfall in KH as well as a significant negative correlation between DJF STJ strength and DJF PDO, suggests a wave response over KH to the direct forcing over the northwest Pacific Ocean. The intensified STJ across KH results in higher frequency of Western disturbances, leading to anomalous moisture convergence and increased DJF precipitation in the region during the PDO−. These findings hold significant implications for the decadal predictability of winter snowfall in KH by the various phases of PDO.