Estimated changes in different forms of precipitation (snow, sleet, and rain) across China: 1961–2016

Abstract

Different forms of precipitation (snow, sleet, and rain) have divergent effects on the Earth's surface water and energy fluxes. Therefore, discriminating between these forms, and exploring their climatology and variations are of significant importance, especially under a changing climate. In this study, a state-of-the-art parameterization scheme with wet-bulb temperature (Tw), relative humidity (RH), surface air pressure, and elevation as inputs was used to estimate the climatologies and trends of the different forms of precipitation and their temperature thresholds across China mainland from 1961 to 2016. The results indicate that on average, only 9.6% and 0.8% of the total precipitation (602.9 mm) over China during 1961–2016 occurred as snow and sleet. The trends of the different forms of precipitation varied greatly from region to region and from season to season. The regionally averaged annual precipitation, rainfall, and snowfall across China significantly increased at rates of 11.4 mm/decade, 11.0 mm/decade, and 1.0 mm/decade, respectively, whereas the annual sleet decreased at a rate of −0.3 mm/decade. The region-wide snow (rain) fraction significantly increased (decreased) in Northwestern China (NWC) and Northern China (NC) but significantly decreased (increased) on the Tibetan Plateau (TP). Given the heterogeneous RH and complex topography, the Tw values at which snow-sleet and sleet-rain occurred with equal frequency—that is, Ts and Tr, varied significantly across China, averaging 0.1 °C and 0.3 °C, respectively. However, most regions experienced significant decreases in the temperature thresholds (especially Tr), with decreasing RH. Almost all of the regions also experienced significant increases in Tw, especially on the TP and during the winter and spring. The adverse combination of the increase in Tw and the decrease in the temperature thresholds resulted in more precipitation falling as rain, although the snowfall slightly increased in some regions.