Snow depth variation and its relation with climate variability in China

Various climatic factors and their interactions affect alterations in China's snow depth. However, a measure of the relative importance of climatic factors regarding the variance in reginal snow depth is lacking. Here, we use a large dataset, quality-controlled daily observations from 1,665 meteorological stations, and statistical regression modelling to identify main drivers and their contributions regarding regional variability and trends in China's snow depth and snow depth-climate relationships from 1951 to 2019. Results show that seasonal snow depth alterations are substantial in China and caused by various climatic drivers. In winter, changes in snow depth across the northwest and northeast of China exhibit a more general increasing trend, while changes in snow depth across the Tibetan Plateau and the remaining regions of China show a more common decreasing trend. The observed positive trends in the northwest and northeast of China mainly respond to augmentation in solid precipitation, explaining nearly 60% of the total interannual variance, and snow accumulation in fall. For the Tibetan Plateau, the negative snow depth anomaly seems to respond to the rising air temperature below the freezing point along with some secular changes in solid precipitation and shallower fall snowpacks. All these trends in winter snow depth over the northwest, northeast, and Tibetan Plateau of China translate into the properties of spring snow depth, accounting approximately for 30% of the total interannual variance in spring snow depth in these regions. In the milder central north and south of China, snow accumulation is not evident. Besides solid precipitation and rising air temperature below the freezing point, atmospheric humidity is also notable for its effect on the interannual variance in winter snow depth in these regions. In spring, however, China's snow depth exhibits a general reduction. Particularly, the central north of China, has experienced the greatest reduction of nearly 50% in spring snow depth during the recent two decades. In fall, on the other hand, changes in snow depth are mostly insignificant in China, but the stronger signal of reduction mainly occurs on the Tibetan Plateau. Moreover, in spring and fall, the negative effect of warming climate on snow depth becomes remarkably more important. It seems that about 13–33% (12–50%) of the total interannual variance in the widespread decrease (insignificant perturbation) of China's spring (fall) snow depth are caused by the rising air temperature below the freezing point.