Abstract:Same as with quantitative precipitation forecast (QPF), snowfall depth forecasting is one important operation of weather forecasting in winter, and the relationship between snowfall depth and precipitation which is called snow to liquid ratio (SLR) abroad is an important parameter required to forecast snowfall depth. In this paper, the main research progresses in variations of SLR and its impact factors at home and aboard in recent decades are reviewed, and the SLR forecast techniques and methods are summarized and compared. Studies indicate that SLR changes obviously in temporal scale, and has seasonal and spatial distribution differences. Air temperature and relative humidity are the two most important meteorological factors affecting SLR. In addition, other meteorological factors such as pressure, vertical motion, surface wind, snowfall weight, solar radiation and snow melting also affect SLR in different degrees. With the development of prediction technology, the methods of SLR forecasting can be summarized as three categories, including climatological, statistical and physical methods. The climatological method is too simple, the application of new statistical methods could improve the prediction ability of SLR, but this method still cannot get rid of the inherent deficiencies of statistics. Comparatively, the method based on the numerical model for predicting instantaneous SLR fits the developing trend toward refinement in snowfall depth forecast in future. At present, observation data of snowfall depth are less and the observation frequency is low in China, thus it is important to effectively carry out the surface snowfall and sounding observation densely, and solve the problem of lack of observation data in the research of SLR. Besides, based on the operational numerical weather prediction model exploring the influence mechanism of meteorological factors on SLR and establishing the forecast operation system suitable for winter snowfall are the developing trend in China.