Pacific Decadal Oscillation-driven interdecadal variability of snowfall over the Karakoram and the Western Himalayas

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 negative phase of PDO are attributed to deep convection and adiabatic cooling near the tropopause in both the northwestern Pacific and the KH region. Additionally, a wave-like pattern characterized by a trough (anomalous cyclone) north of the KH and a ridge (anomalous Tibetan Plateau anticyclone) east of the KH in the upper atmosphere, along the northward shift of the DJF subtropical westerly jet (STJ), was observed. A strong positive correlation between the DJF STJ strength and DJF snowfall in the KH, as well as a significant negative correlation between the DJF STJ strength and the DJF PDO, suggests a wave response over the KH to the direct forcing over the northwestern Pacific Ocean. The intensified STJ across the 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 the KH by the various phases of the PDO.