Change in the potential snowfall phenology: past, present, and future in the Chinese Tianshan mountainous region, Central Asia
Authors: Li Xuemei , Liu Xinyu , Zhao Kaixin , Zhang Xu , Li Lanhai 
Published: June 2023

Abstract. The acceleration of climate warming has led to a faster
solid–liquid water cycle and a decrease in solid water storage in cold
regions of the Earth. Although snowfall is the most critical input for the
cryosphere, the phenology of snowfall, or potential snowfall phenology
(PSP), has not been thoroughly studied, and there is a lack of indicators
for PSP. For this reason, we have proposed three innovative indicators,
namely, the start of potential snowfall season (SPSS), the end of potential
snowfall season (EPSS), and the length of potential snowfall season (LPSS),
to characterize the PSP. We then explored the spatial–temporal variation in
all three PSP indicators in the past, present, and future across the Chinese
Tianshan mountainous region (CTMR) based on the observed daily air
temperature from 26 meteorological stations during 1961–2017/2020 combined
with data from 14 models from CMIP6 (Phase 6 of the Coupled Model
Intercomparison Project) under four different scenarios (SSP126, SSP245,
SSP370, and SSP585, where SSP represents Shared Socioeconomic Pathway) during 2021–2100. The study showed that the SPSS, EPSS,
and LPSS indicators could accurately describe the PSP characteristics across
the study area. In the past and present, the potential snowfall season
started on 2 November, ended on 18 March, and lasted for about
4.5 months across the CTMR on average. During 1961–2017/2020,
the rate of advancing the EPSS (−1.6 d per decade) was faster than that of
postponing the SPSS (1.2 d per decade). It was also found that there was a
significant delay in the starting time (2–13 d) and advancement in the
ending time (1–13 d), respectively, resulting in a reduction of 3–26 d
for the LPSS. The potential snowfall season started earlier, ended later,
and lasted longer in the north and center compared with the south. Similarly,
the SPSS, EPSS, and LPSS indicators are also expected to vary under the four
emission scenarios during 2021–2100. Under the highest emission scenario,
SSP585, the starting time is expected to be postponed by up to 41 d,
while the ending time is expected to be advanced by up to 23 d across the
study area. This change is expected to reduce the length of the potential
snowfall season by up to 61 d (about 2 months), and the length of the
potential snowfall season will only last 2.5 months in the 2100s
under the SSP585 scenario. The length of the potential snowfall season in
the west and southwest of the CTMR will be compressed by more days due to a
more delayed starting time and an advanced ending time under all four
scenarios. This suggests that, with constant snowfall intensity, annual total
snowfall may decrease, including the amount and frequency, leading to a
reduction in snow cover or mass, which will ultimately contribute to more
rapid warming through the lower reflectivity to solar radiation. This
research provides new insights into capturing the potential snowfall
phenology in the alpine region and can be easily extended to other
snow-dominated areas worldwide. It can also help inform snowfall monitoring
and early warning for solid water resources.