Duration of vegetation green-up response to snowmelt on the Tibetan Plateau

Abstract. The Tibetan Plateau (TP) is characterized by abundant snow and heightened sensitivity to climate change. Although the impact of snowmelt on vegetation green-up is well recognized, the duration of the vegetation response to snowmelt on the TP remains unclear. This study calculates the time differences between the green-up date and the start of snowmelt from 2001 to 2018 on the TP, denoted as ∆T. Exploratory spatial data analysis and Mann Kendall test were then applied to investigate the spatiotemporal distribution feature of ∆T. Subsequently, heatmaps, box plots, partial correlation, and multiple linear regression analyses were employed to examine the impact of spring mean temperature, spring total rainfall, and daily snowmelt on ∆T. The results reveal that the mean ∆T across the TP was 36.7 days, with a spatially clustered distribution: low-low clusters in the Hengduan Mountains and high-high clusters in the Bayankara and Himalayas Mountains. Additionally, ∆T shortened with increasing spring mean temperature, spring total rainfall, and daily snowmelt, which can explain 15.7 %, 16.1 %, and 25.8 % of ∆T variation, respectively. In arid areas and regions with low vegetation, daily snowmelt was the dominant factor of ∆T for 74 % and 66 % of the regions, respectively. Conversely, spring mean temperature was the predominant factor for 65 % and 59 % of humid areas and regions with high vegetation. Our findings enhance the understanding of vegetation responses to snowmelt and provide a scientific basis for further research on the stability of alpine ecosystems and the impacts of climate change on the TP.