Three classical freezing rain processes over southern China were simulated by observation data and CAMS mesoscale cloud model. Characteristics of atmospheric stratification and cloud physics of the freezing rain and mechanism of freezing rain formation are analyzed. The results show that: (1) a necessary condition for exist freezing rain was the presence of the temperature inversion layer. The inversion layer with high humidity in lower atmosphere often associated with freezing rain. (2) Formation of freezing rain needed to meet three main conditions: freeze layer existed in the upper troposphere, a warm layer and temperature inversion layer existed blow the freeze layer, and cooling layer (temperature below 0 ℃) with high humidity existed near the surface. (3) Two different types of temperature stratification were existed during freezing rain, which are ‘cold-warm-cold’ and ‘warm-cold’ stratification. Corresponding to two types of stratification, two different clouds microphysical structures were existed and two different mechanism of freezing rain formation. Consideration of stratification (‘cold-warm-cold’ layer), the cloud thickness was deeper over Hunan Province on 28 January 2008 and Jiangxi Province on 5 January 2010, and cloud has large amount of ice-phase particles. So clouds belonged to mixed-phase cloud. Freezing rain over Hunan and Jiangxi Provinces was formed by ice-crystal mechanisms (the melting process). That is, freezing rain developed as falling snow encountered a layer of warm air then the snow completely melted and became rain. As the rain continued to fall, it passes through a thin layer of cold air just above the surface and cools to a temperature below freezing and formed supercooled drops. When the supercooled drops strike ground, or anything else below 0 ℃, they instantly freeze, forming freezing rain. Clouds above freezing rain area over Hunan and Jiangxi Provinces belonged to mixed-phase cloud. However, clouds above freezing rain area over Guizhou Province on 28 January and 9 February 2008 belonged to warm cloud: the cloud thickness was thinner, cloud top temperature was higher, and clouds have little ice-phase particles. Consideration of stratification (‘warm-cold’ layer), freezing rain over Guizhou Province was formed by supercooled warm-rain processes (collision-coalescence process). Supercooled raindrops developed as microscopic cloud droplets collect one another as they fall. Ice processes were not involved in the formation of these raindrops. (4) Over the different freezing rain zone in the same weather systems, the different temperature stratification, cloud microphysical structure and formation mechanism of freezing rain can exist in different types of cloud. The freezing rain zone with same feature can also exist in different weather systems, namely temperature stratification of freezing rain formation, cloud microphysical structure and the mechanism of freezing rain formation are same.
[1]陈天锡, 穆晓涛. 驻马店地区冻雨天气特征的分析和预报[J]. 气象, 1993, 19(2): 33-36.
[2]吕胜辉, 王积国, 邱菊. 天津机场地区冻雨天气分析[J]. 气象科技, 2004, 6: 456-460.
[3]高洋, 吴统文, 陈葆德. 2008年1月我国南方冻雨过程的热力异常及其形成原因[J].高原气象, 2011, 30(5): 1526-1533.
[4]丁一汇, 王遵娅, 宋亚芳.中国南方2008年1月罕见低温雨雪冰冻灾害发生的原因及其与气候变暖的关系[J].气象学报, 2008, 66(5): 808-825.
[5]黎惠金,韦江红,覃昌柳, 等. 2008年广西罕见低温雨雪冰冻天气成因及数值预报产品性能分析[J]. 气象研究与应用, 2008, 29(1): 16-19.
[6]高辉, 陈丽娟, 贾小龙, 等. 2008年1月我国大范围低温雨雪冰冻灾害分析Ⅱ.成因分析[J]. 气象, 2008, 34(4): 101-106.
[7]王东海,柳崇健,刘英, 等. 2008年1月中国南方低温雨雪冰冻天气特征及其天气动力学成因的初步分析[J].气象学报, 2008, 66(3): 405-422.
[8]杨贵名, 孔期, 毛冬艳, 等. 2008年初“低温雨雪冰冻”灾害天气的持续性原因分析[J].气象学报, 2008, 66(5): 836-849.
[9]郑婧, 许爱华, 许彬. 2008年江西省冻雨和暴雪过程对比分析[J].气象与减灾研究, 2008, 2: 29-35.
[10]宗志平, 马杰. 2008年初冻雨强度变化以及与逆温层特征之间的关系[J].气象, 2011, 37（2）: 156-160.
[11]孙建华, 赵思雄. 2008年初南方雨雪冰冻灾害天气的大气层结和地面特征的数值模拟[J].气候与环境研究, 2008, 23(4): 510-519.
[12]苗春生, 赵瑜, 王坚红. 080125南方低温雨雪冰冻天气持续降水的数值模拟[J].大气科学学报, 2010, 33(1): 25-33.
[13]黎惠金,李江南, 林文实, 等. 2008年初南方冻雨云物理过程的模拟研究[J].高原气象, 2011, 30(4): 942-950.
[14]Brooks C F. The nature of sleet and how it is formed[J]. Mon Wea Rev, 1920: 48, 69-73.
[15]Marwitz J D. Winter storms over the San Juan Mountains. PartⅠ: Dynamical processes[J]. J Appl Meteor, 1980, 19: 913-926.
[16]Cooper W A, Marwitz J D. Winter storms over the San Juan Mountains. Part Ⅲ: Seeding potential[J]. J Appl Meteor, 1980, 19: 942-949.
[17]Forbes G S, Anthes R A, Thomson D W. Synoptic and mesoscale aspects of an Appalachian ice storm associated with cold-air damming[J]. Mon Wea Rev, 1987, 115: 564-591.
[18]Dunn L B. Cold air damming by the front range of the Colorado Rockies and its elationship to locally heavy snow[J]. Wea Forecasting, 1987, 2: 177-189.
[19]Dunn L B. Evidence of ascent in a sloped barrier jet and an associated heavy snow band[J]. Mon Wea Rev, 1992, 120: 914-924.
[20]Robert M R, Mohan K R, Tokay A. Synoptic and mesoscale structure of a severe freezing rain event: The St.Valentine's Day ice storm[J]. Wea Forecasting, 1996, 6: 183-208.
[21]Szeto K K, Tremblay A, Guan H, et al. The mesoscale dynamics of freezing rain storms over eastern Canada[J]. J Atmos Sci, 1999, 56(10): 1261-1281.
[22]John C Jr. A climatology of freezing rain in the great lakes region of North America[J]. Mon Wea Rev, 2000, 128(10): 3574-3588.
[23]Rauber L S, Olthoff M K, Ramamurthy, et al. Further investigation of a physically based, non-dimensional parameter for discriminating between locations of freezing rain and ice pellets[J]. Wea Forecasting, 2001, 16: 185-191.
[24]Cortinas. An analysis of freezing rain, freezing drizzle, and ice pellets across the United States[J]. Wea Forecasting, 2004, 19: 377-390.
[25]Bennett W J. The sleet storm in northern New York, March 25-27[J]. Mon Wea Rev, 1913, 41: 372-373.
[26]Meisinger C L. The precipitation of sleet and the formation of glaze in the eastern United States, January 20 to 25, 1920, with remarks on forecasting[J]. Mon Wea Rev, 1920, 48: 73-80.
[27]Henry A J. The great glaze storm of 21-23 February 1922 in the upper lake region: discussion of general conditions[J]. Mon Wea Rev, 1922, 50: 77-82.
[28]Martner B E, Snider J B, Zamora R J, et al. A remote sensing view of a freezing rainstorm[J]. Mon Wea Rev, 1993,121: 2562-2577.
[29]Rauber R M, Ramamurth M K, Tokay A. Synoptic and mesoscale structure of a severe freezing rain event: The St. Valentine's day ice storm[J]. Wea Forecasting, 1994, 9: 183-208.
[30]Czys R R, Scott R W, Tang K C, et al. A physically based, nondimensional parameter for discriminating between locations of freezing rain and sleet[J]. Wea Forecasting, 1996, 11: 591-598.
[31]Robert M, Olthoff L S, Ramamurthy M K. The relative importance of warm rain and melting processes in freezing precipitation events[J]. J Appl Meteor, 2000, 39:1185-1195.
[32]Huffman G J, Norman G A Jr. The supercooled warm rain process and the specification of freezing precipitation[J]. Mon Wea Rev, 1988, 116: 2172-2182.
[33]Bocchieri J R. The objective use of upper air soundings to specify precipitation type[J]. Mon Wea Rev, 1980, 108: 596-603.
[34]Rauber R M, Olthoff L S, Ramamurthy M K, et al. The relative importance of warm rain and melting processes in freezing precipitation events[J]. J Appl Meteor, 2000, 39: 1185-1195.
[35]Tremblay A, Glazer A. An improved modeling scheme for freezing precipitation forecasts[J]. Mon Wea Rev, 2000, 128: 1289-1308.
[36]Rasmussen R M. Freezing drizzle formation in stably stratified layer clouds: the role of radiative cooling of cloud droplets, cloud condensation nuclei, and ice initiation[J]. J Atmos Sci, 2002, 59: 837-860.
[37]周毓荃, 陈英英, 李娟, 等. 用FY-2C/D卫星等综合观测资料反演云物理特性产品及检验[J]. 气象, 2008, 34(12): 27-35.
[38]楼小凤. MM 5模式的新显式云物理方案的建立和耦合及原微物理方案的对比分析[D]. 北京: 北京大学, 2002.
[39]胡志晋, 何观芳.积雨云微物理过程的数值模拟（一）微物理模式[J].气象学报, 1987, 45(4): 467-484.
[40]孙晶, 楼小凤, 胡志晋. 祁连山冬季降雪个例模拟分析（Ⅰ）: 降雪过程和地形影响[J].高原气象, 2009, 28（3）: 485-495.
[41]孙晶, 楼小凤, 史月琴, 等. 祁连山冬季降雪个例模拟分析（Ⅱ）: 人工催化试验[J].高原气象, 2009, 28（3）: 496-506.
[42]刘卫国, 刘奇骏.祁连山夏季地形云结构和云微物理过程的模拟研究(I): 模式云物理方案和地形云结构[J].高原气象, 2007, 26（1）: 1-15.
[43]刘卫国, 刘奇骏.祁连山夏季地形云结构和云微物理过程的模拟研究(II): 云微物理过程和地形影响[J]. 高原气象, 2007, 26（1）: 16-29.
