Warming Triggers Snowfall Fraction Loss Thresholds in High-Mountain Asia

Snowfall, a crucial indicator of climate change, is essential for freshwater supply and glacier health. Accurately classifying precipitation types, especially in the rain-snow transition zone, is vital for understanding climate impacts. While previous studies have used snowfall fractions for classification, they often overlook the nuances of regional variations and tipping points. High Mountain Asia (HMA), with its complex topography and rapid warming, is an ideal region to study snowfall thresholds. This research aims to: (1) identify key snowfall fraction thresholds to categorize HMA into distinct precipitation dominance categories, (2) project the future evolution of these dominant precipitation types using CMIP6 model data, including estimates of transition times for various precipitation types, and (3) assess uncertainties in snowfall fraction predictions by comparing temperature- and temperature-relative humidity-based precipitation phase identification methods. This research can provide a valuable scientific resource for identifying climate-sensitive areas and regions at high risk of snowfall loss within HMA.

In this study, a continuous piecewise linear regression model was employed to classify HMA into four distinct precipitation regimes: insensitive snowfall-dominated areas, sensitive snowfall-dominated areas, sensitive rainfall-dominated areas, and insensitive rainfall-dominated areas. Our results show that future warming will increase the sensitivity of winter and spring snowfall to climate change, whereas summer and autumn snowfall will become less sensitive. All four precipitation regimes exhibit an upward shift to higher elevations, with varying rates of elevation gain across regions and seasons. Temperature is the primary driver of snowfall loss, whereas relative humidity mitigates it. This study identifies high-risk areas vulnerable to snowfall loss, guiding the development of effective mitigation strategies.