Snowfall in mountainous areas provides indispensable water sources for arid and semi-arid watersheds. Changes in snowfall and snowmelt regimes have significantly impacted the water resources' variations and management. This study addresses the ratio of snowfall to precipitation (S/P) in the Tian Shan Mountains, China. It aims to examine changes in S/P ratio and its synchronization with climate change. The results show that the average S/P ratio experienced a downward trend under the precipitation and snowfall increases as well as temperature increases during the cold seasons in 1961-2010. Spatially, the S/P ratios show an increasing trend in the Boertala Valley and the southern slope of the middle Tian Shan Mountains, but a decreasing trend in Yili Valley, and the western and the northern slope of the middle Tian Shan Mountains. The S/P ratios decreased significantly in middle altitudes with elevation ranging from 1500 to 2500 m, but either decreased or increased at elevations below 1500 m due to a temperature inversion in the elevation belt. In high altitudes with elevation over 3500 m, the magnitudes of the decreased S/P ratios were small because the temperature was always below freezing. The decreases in S/P ratio was mainly attributed to the relative changes in snowfall (dS/S) being less than that in precipitation (dP/P), whereas the increases in S/P ratio resulted from the relative changes in snowfall (dS/S) being more than that in precipitation (dP/P). Temperature increases have also lead to the decreases in S/P ratios to some extent.

In the Tibetan Plateau (TP), the changes of lake ice phenology not only reflect regional climate change, but also impose substantial ecohydrological impacts on the local environment. Due to the limitation of ground observation, remote sensing has been used as an alternative tool to investigate recent changes of lake ice phenology. However, uncertainties exist in the remotely sensed lake ice phenology owing to both the data and methods used. In this paper, three different remotely sensed datasets are used to investigate the lake ice phenology variation in the past decade across the Tibetan Plateau, with the consideration of the underlying uncertainties. The remotely sensed data used include reflectance data, snow product, and land surface temperature (LST) data of moderate resolution imaging spectroradiometer (MODIS). The uncertainties of the three methods based on the corresponding data are assessed using the triple collocation approach. Comparatively, it is found that the method based on reflectance data outperforms the other two methods. The three methods are more consistent in determining the thawing dates rather than the freezing dates of lake ice. It is consistently shown by the three methods that the ice-covering duration in the northern part of the TP lasts longer than that in the south. Though there is no general trend of lake ice phenology across the TP for the period of 2000–2015, the warmer climate and stronger wind have led to the earlier break-up of lake ice.

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