中文摘要：

利用2000-2013年冬季回流形势36次降水个例的高空、地面观测资料及济南、青岛的降水资料,研究了山东回流形势的环流特征,并按中间暖层和低层冷层的厚度进行了分型。在分型的基础上,探讨了不同形势下温度、厚度的垂直变化特征,获得了不同降水相态下的温度和厚度预报指标。结果表明：（1）回流形势可分为3种,即：回流Ⅰ型、回流Ⅱ型和浅回流型,其中浅回流型又可分为冷层薄浅回流与暖层薄浅回流。（2）直接降雪时,内陆地区各层的温度阈值为T_（850）≤-4℃,T_（925）≤-2℃,T_（1000）≤0℃或T地面≤1℃;但是沿海地区更要确保地面温度〈0℃。（3）无论内陆还是沿海,当T_（850）≤-3℃,T_（925）≤-1℃,T_（1000）≤0℃或T地面≤1℃时,要考虑降水相态由雨转为雨夹雪或雪;（4）直接降雪的厚度指标：回流Ⅰ型与回流Ⅱ型,冷层H_（850-1000）为127~130 dagpm,暖层H_（500-700）为252~256 dagpm;冷层薄浅回流,冷层H_（925-1000）为61~64 dagpm,暖层H_（500-850）为403~413 dagpm;暖层薄浅回流,冷层H_（700-1000）为279~284 dagpm,暖层H_（500-700）为250~260 dagpm。雨转雪时,回流Ⅰ型与回流Ⅱ型,冷层H_（850-1000）为127~130 dagpm,暖层H_（500-700）为255~264 dagpm,浅回流型雨转雪过程个例太少,厚度指标有待以后关注。

英文摘要：

Based on sounding and surface observation data of 36 return-flow precipitation cases and precipitation data in Jinan and Qingdao during 2000 to 2013,this paper reveals circulation features,vertial characteristics of temperature and height thickness of return-flow precipitation in Shandong province in winter,and return-flow synoptic situations are typed by warm layer in the middle troposphere and cold layer in lower troposphere. The results show that return-flow situations can be divided into three types of return-flowⅠ,return-flowⅡand thin return-flow,respectively. Thin return-flow is composed of thin cold return-flow and thin warm return-flow warm.To pure snowfall,temperature thresholds in inland are T_（850）≤-4 ℃,T_（925） ≤-2 ℃,T_（1000） ≤0 ℃ or Tground ≤1 ℃. It is more important that surface temperature is less than 0 ℃ in coastal areas. Whether in coastal region or inland,rain turns to sleet or snow when temperature indexes show that T_（850）≤-3 ℃,T_（925） ≤-1 ℃,T_（1000） ≤0 ℃ or Tground ≤1 ℃. Thickness clues are various during the pure snowfall that H_（850-1000） is from 127 to 130 dagpm and H_（500-700） is from 252 to 256 dagpm in return-flowⅠand return-flowⅡ. In addition,H_（925-1000） shows from 61 to 64 dagpm and H_（500-850） shows from 403 to 413 dagpm in thin cold return-flow air while H_（700-1000） embodies from 279 to 284 dagpm and H_（500-700） embodies from 250 to 260 dagpm in thin warm return-flow. When rain turns to snow,H_（850-1000） marks from 127 to 130 dagpm and H_（500-700） marks from 252 to 256 dagpm. But phase converted cases of thin return-flow are too little,thinkness indicators need to focus on later.