Intensifying heatwave events affect snow phenology over the Tibetan Plateau

Abstract

Snow phenology change has significant impacts on the climate, hydrology, and ecology over the Tibetan Plateau (TP). In the context of global climate change, heatwave events over the TP are becoming increasingly intense. However, it remains unclear how snow phenology in the region responds to the heatwave events and multiple meteorological factors, and what the possible mechanisms are. Based on daily cloud-free snow cover products and hourly high-resolution meteorological data, this study systematically investigated the spatiotemporal variations and spatial correlations of snow phenology parameters (snow onset date − SOD, snow end date − SED, and snow duration days − SDD) and heatwave indicators (frequency of heatwave − HWF, total number of heatwave days − HWN, intensity of heatwave − HWI, and duration of heatwave − HWD across the entire TP and 12 sub-basins for the hydrological year from 2000 to 2021. The potential mechanism of how heatwave indicators and multiple meteorological factors influence snow phenology was further explored using the structural equation model (SEM). The results indicate that the interannual variations of snow phenology over the TP are mainly characterized by a delayed SOD (significant delay accounts for 13.61 %), an advanced SED (significant advance accounts for 13.20 %), and a shortened SDD (significant shorten accounts for 14.77 %), particularly for Brahmaputra (BRA) and Salween (SAL) basins. All heatwave indicators (HWF, HWN, HWI and HWD) exhibit a significant increasing trend, with 66.75 %, 67.60 %, 62.29 % and 28.83 % of the area significantly increased, respectively, and these trends were observed in all basins. There is a clear correlation between snow phenology and heatwave indicators—more frequent, intense, and prolonged heatwave events (i.e., higher HWF, HWN, HWI, and HWD) lead to later SOD, earlier SED, and shortened SDD, with HWN being the most indicative of the impact of heatwave events on snow phenology. In addition, among various meteorological factors, specific humidity and downward longwave radiation are key drivers of snow phenology change in most sub-basins of the TP. The impacts of heatwave indicators and meteorological factors on snow phenology vary across different sub-basins, but in most basins, they primarily influence SED, thereby affecting snow persistence (i.e., SDD). These findings will provide scientific support for climate change adaptation and water resource management policy-making in global alpine regions.