Declining snowfall fraction in the alpine regions, Central Asia

Abstract

in a warming climate, precipitation (p) is less likely to occur as snowfall (S). change in the snowfall fraction (S/P) is currently assumed not only influences the accumulation and ablation of glaciers, but also influences the streamflow and water resources significantly in mountainous regions. However, until now, most studies have focused on precipitation magnitude and its frequency changes, while seasonal shifts in precipitation types have been mostly neglected. This paper employs the threshold temperature method in combination with multi-source dataset (APHRODITE, CPC and meteorological stations) analysis to determine snowfall proportions in precipitation in the tienshan Mountains, central Asia, during 1960-2017. The results indicated that temperature-induced precipitation shifting from snow to rain. The S/P experienced an overall declining trend, increasing at a rate of 0.6%/decade prior to the mid-1990s, followed by a downward trend at a rate of −0.5%/decade. The S/P decreased mainly at low and middle altitudes (between 1500 and 3500 m). At higher altitudes (over 3500 m), the magnitudes of the decreased S/P ratios were small or even increased due to the temperature always being below freezing. Decreases in S/P are always associated with decreases in annual streamflow in the glacier/ snow melt recharged rivers.Precipitation over alpine regions can occur in different phases of liquid and solid. Snowfall, as the most important component of solid precipitation, is a key part of hydrological processes in the mountains during the cold season. It is also regarded as an indicator that reflects climatic change due to its high sensitivity to alterations in temperature and precipitation 1,2 . The snowfall fraction (S/P) is the ratio of snowfall (S) to precipitation (P), with changes in the S/P depending on alterations in snow and precipitation amounts 3,4 . As there may exist inconsistent changes in snowfall and precipitation, the snowfall fraction can be used as another effective indicator to reflect climate change 5 .Most of the previous studies use temperature or wet-bulb temperature and relative humidity to define thresholds which demarcate the solid and liquid types of precipitation 6-8 . As global temperatures continue to warm, many regions experienced a decreased S/P. The S/P has shown a significant decreasing trend across the New England states 9 , Switzerland 5 , the continental United States 10,11 , the Tibetan Plateau 8,12 , and the Chinese Tienshan Mountains 3 . The S/P has a strong influence on mountainous hydrological processes. The performance of water resource management systems is highly related to changes in the S/P in the regions where the land surface hydrological process is dominated by snow accumulation in winter and melt in spring 6 . Decreases in the S/P can lead to increases in water loss during winter or early spring, whereas increases in the S/P indicate that much more water is being stored as snows until the temperature exceeds the melt point 4,13 . Two widely anticipated changes in the hydr...

Effect of sub‐cloud evaporation on precipitation in the Tianshan Mountains (Central Asia) under the influence of global warming

“…Global warming influences the precipitation in two ways. First, the fraction of snow/ rainfall decreases with increasing temperature, especially in early winter and early spring (Y. N. Chen et al, 2016;Li et al, 2020). Meanwhile, precipitation in early winter and early spring is characterised with small precipitation amounts and low relative humidity, which increases the effect of sub-cloud evaporation.…”

“…This results in severe challenges to the population in the area that rely on the melt water in the long run (Pritchard, 2019). The mid-mountain is an area with the largest amount of precipitation in the Tianshan Mountains and is the most sensitive to climate change (Li et al, 2020). Because of global warming, the precipitation in the Tianshan Mountains will suffer more from evaporation and become more complex.…”

Trends and variability in snowmelt in China under climate change

“…Additionally, because of the lack of meteorological data and the fact that it has very little snowfall, Taiwan was not considered in this study. The snow cover types in China can be divided into five types: prairie, taiga, tundra, mountain and ephemeral types (Li et al, 2020) (Fig. 1c).…”

Reply on RC1

“…Han et al (2021) used rainfall and snowfall temperature thresholds to identify precipitation types in the Lancang River basin in Southwest China, and obtained R 2 values between the simulated snowfall and the snowfall observed at three meteorological stations of 0.42, 0.34 and 0.61, respectively; in this study, the R 2 values at the same stations were 0.72, 0.46 and 0.39, respectively. Li et al (2020) Snow depth was the worst-performing model output, this was mainly for the following reasons. (1) The model was performed on a monthly scale, whereas the output data were compared with the observed snow depth measured on the last day of each month, which increased the error.…”