Abstract:By using surface observations and sounding data, statistic studies were carried out on synoptic systems, timing of type changes, and temperature variations during 24 snowfall events accompanied by precipitation type reversal phenomena in Shandong province from 1999 to 2013. The results show that precipitation type reversal may occur under synoptic systems of cold fronts, Jianghuai Cyclone, Huanghe Cyclone and warm shear lines, and may not occur under system of returnflow in Shandong province. Precipitation type reversal mainly occurs from November to April of the next year, concentrates in December and January, with highest frequency in December. Precipitation type reversal also has obvious diurnal variations, with the highest frequency around 14:00 BST and lowest frequency during the time period from 23:00 BST to 05:00 BST the next day. During precipitation type reversal process, one of the most typical changes is 2-m temperature rising, which is usually between 1 to 2 ℃. There are at least two warming layers below 850 hPa. During precipitation type reversal, the most effective indicator is 2-m temperature, which is around 0 ℃ (-1 ℃ at lowest) as snowing, a little higher than that of usual snowfalls. During snow, the temperature at 1 000 hPa is near 0 ℃. Low level temperature rising, caused by warm advection and temperature diurnal variation, may lead to precipitation type reversal. When the warm advection is weak, the diurnal variation of temperature will play an important role. There are significant differences in area and timing of precipitation type reversal under different synoptic systems. Therefore, the warm advection on low troposphere and temperature diurnal variation should be taken into consideration in making precipitation type forecast especially when the temperature is around the threshold for snow. Special attention should be paid to 2-m temperature and especially in time period of afternoon.