2014年4月13-15日北疆出现了大范围雨转雪天气和强降雪过程，给当地工农牧业及人民生活造成严重影响。对这次过程，利用天气学诊断方法，分析了其发生发展过程，并得到此次灾害性天气过程中雨雪相态转换和降水强度的预报指标。结果显示：（1）此次天气过程是在中亚低涡两次生成、发展和减弱过程中出现的。（2）中低层温度变化是预报北疆春季降水相态转换的关键因子和指标，中层温度可区分雪和雨夹雪，T500 < -25℃、T700 < -12℃可判定为雨夹雪转雪；低层温度可区分雨和雨夹雪，T850 < -2℃和T925 < 2℃时雨转雨夹雪，T850 < -4.5℃用来判别雨夹雪转雪。（3）春季北疆沿天山一带和天山山区的降水中水汽凝结起主要作用，中低层水汽冷凝结是影响降水强度的重要因子，水汽条件越好、冷空气越强、凝结厚度越厚、持续时间越长，则降水强度越强，水汽冷凝结强度决定了降水强度的大小。
A large-scale rain followed by snow and heavy snow process happened in northern Xinjiang from 13 to 15 April 2014, which has brought serious impact on local agricultural, works and people's life. Using the diagnosis method of the weather, the forecast index of phase transformation between rain and snow as well as rainfall intensity was studied. The result shows:(1) Change of temperature at middle-low level is the key factor and index to Forecast precipitation phase transformation in spring in Northern Xinjiang. (2) Temperature at the middle level is a key factor to distinguish between the snow and sleet. Sleet turning to snow when the temperature is less than -25℃ on 500 hPa and less than -12℃ on 700 hPa; Temperature at the low level can distinguish between the rain and sleet, rain turning to sleet in the case of the temperature less than -2℃ on 850 hPa and less than 2℃ on 925 hPa. Additionlly, the forecast index of sleet turning to snow when the temperature is less than -4.5℃ on 850 hPa. (3) Cooling condensation of water vapor plays an important role on precipitation process in spring over the northern edge of the Northern Xinjiang and the Tianshan mountainous. Cooling condensation of the lower water vapor is an important factor affecting the rainfall intensity. There are more water vapor、stronger cold air、thicker condensation which can induce longer and stronger rainfall. The rainfall intensity is decided by the cooling condensation of water vapor.
[1]Zhang Linna, Guo Rui, Zeng Jian, et al. 2013. Research on discrimination criterion of precipitation types in Beijing in winter[J]. Plateau Meteor, 32(6):1780-1786. DOI:10.7522/j.issn.1000.0534.2012.00147.<br/>张琳娜, 郭锐, 曾剑, 等. 2013.北京地区冬季降水相态的识别判据[J].高原气象, 32(6):1780-1786.
[2]Sun Yan, Yan Wenlian, Yin Dongping, et al. 2013. Climatic characteristics and forecast of precipitation phase in winter of Jiangsu[J]. J Meteor Sci, 33(3):325-332. DOI:10.3969/2012jms.0113.<br/>孙燕, 严文莲, 尹东屏, 等. 2013.江苏冬季降水相态气候分布特征及预报方法探讨[J].气象科学, 33(3):325-332.
[3]Zhang Bei, Yin Dongping, Sun Yan, et al. 2014. Mechanism analysis of multiphase precipitation during a cold wave process[J]. Plateau Meteor, 33(1):190-198. DOI:10.7522/j.issn.1000-0534.2012.00171.<br/>张备, 尹东屏, 孙燕, 等. 2014.一次寒潮过程的多种相态降水机理分析[J].高原气象, 33(1):190-198.
[4]Liao Xiaonong, Zhang Linna, He Na, et al. 2013. Analys is on the mechanism of the 17 March 2012 precipitation type variety in Beijing[J]. Meteor Mon, 39(1):28-38. DOI:10.7519/j.issn.1000-0526.2013.01.004.<br/>廖晓农, 张琳娜, 何娜, 等. 2013.2012年3月17日北京降水相态转变的机制讨论[J].气象, 39(1):28-38.
[5]You Fengchun, Guo Lixia, Shi Yinshan, et al. 2013. Discrimination index of precipitation phase state and its verification in Beijing[J]. J Meteor Environ, 29(5):49-54. DOI:10.3969/j.issn.1673-503X. 2013.05.008.<br/>尤凤春, 郭丽霞, 史印山, 等. 2013.北京降水相态判别指标及检验[J].气象与环境学报, 29(5):49-54.
[6]Gao Songying, Li Huilin, Song Lili, et al. 2014. Study on criteria for winter precipitation phase states in Dandong[J]. J Meteor Environ, 30(2):38-44. DOI:10.3969/j.issn.1673-503X. 2014.02.005.<br/>高松影, 李慧琳, 宋丽丽, 等. 2014.丹东冬季降水相态判据研究[J].气象与环境学报, 30(2):38-44.
[7]Miao Aimei, Dong Wenxiao, Jia Lidong, et al. 2014. The statistical characteristics and conceptual model of different phase precipitation in recent 30 years in Shanxi Province[J]. J Arid Meteor, 32(1):23-31. DOI:10.11755/j.issn.1006-7639.2014.01.0023.<br/>苗爱梅, 董文晓, 贾利东, 等. 2014.近30a山西不同相态降水的统计特征及概念模型[J].干旱气象, 32(1):23-31.
[8]Qi Liangbo, Zhang Ying. 2012. Researeh on winter precipitation types diserimination criterion in eastern China[J]. Meteor Mon, 38(1):96-102. DOI:10.7519/j.issn.1000-0526.2012.03.009.<br/>漆梁波, 张瑛. 2012.中国东部地区冬季降水相态的识别判据研究[J].气象, 38(1):96-102.
[9]Yang Chengfang, Jiang Peng, Zhang Shaolin, et al. 2013. Analysis on temperature of precipitation types in cold seasons in Shandong[J]. Meteor Mon, 39(3):355-361. DOI:10.7519/j.issn.1000-0526.2013.03.010.<br/>杨成芳, 姜鹏, 张少林, 等. 2013.山东冬半年降水相态的温度特征统计分析[J].气象, 39(3):355-361.
[10]Zheng Lina, Yang Chengfang, Liu Chang. 2016. Study on circulation features of return-flow and related precipitation types during cold seasons in Shandong[J]. Plateau Meteor, 35(2):520-527. DOI:10.7522/j.issn.1000-0534.2015.00055.<br/>郑丽娜, 杨成芳, 刘畅. 2016.山东冬半年回流降雪形势特征及相关降水相态[J].高原气象, 35(2):520-527.
[11]Zhang Qin, Ding Zhiying, Yang Chengfang, et al. 2015. Diagnostic analysis of a historical extreme snow process in Shandong[J]. Plateau Meteor, 34(4):1131-1138. DOI:10.7522/j.issn.1000-0534.2014.00009.<br/>张芹, 丁治英, 杨成芳, 等. 2015.山东一次历史极端降雪过程的诊断分析[J].高原气象, 34(4):1131-1138.
[12]Liu Jianyong, Gu Sinan, Xu Difeng. 2013. Simulation study on precipitation phase state in two snowfall processes of south China[J]. Plateau Meteor, 32(1):179-190. DOI:10.7522/j.issn.1000-0534.2012.00018.<br/>刘建勇, 顾思楠, 徐迪峰. 2013.南方两次降雪过程的降水相态模拟研究[J].高原气象, 32(1):179-190.
[13]Liu Yulu, Huang Yong. 2013. Study of Huangshan Mountain terrain on precipitation enhancement condition[J]. Plateau Meteor, 32(2):608-615. DOI:10.7522/j.issn.1000-0534.2012.00059.<br/>刘裕禄, 黄勇. 2013.黄山山脉地形对暴雨降水增幅条件研究[J].高原气象, 32(2):608-615.
[14]Zhai Liping, Wei Ming. 2012. The formation mechanism of atmospheric environment for a heavy snowstorm event[J]. J Meteor Sci, 32(6):638-645. DOI:10.3969/2012jms.0050.<br/>翟丽萍, 魏鸣. 2012.一次大范围暴雪天气的大气环境形成机制研究[J].气象科学, 32(6):638-645.
[15]Zhao Guixiang, Zhao Jianfeng, Yang Dong, et al. 2013. Characteristics of cloud chart and environment field on a heavy rain process in Shanxi Province[J]. Plateau Meteor, 32(6):1747-1757. DOI:10.7522/j.issn.1000-0534.2012.00163.<br/>赵桂香, 赵建峰, 杨东, 等. 2013.山西一次大暴雨过程云图及环境场的特征分析[J].高原气象, 32(6):1747-1757.
[16]Lü Keli, Zhao Deming. 1997. Effects of both the condensation process of moisture and upper and low-level jets on the cold-front circulation[J]. Chinese J Atmos Sci, 21(3):317-323.<br/>吕克利, 赵德明. 1997.水汽凝结过程与高低空急流对冷风环流的作用[J].大气科学, 21(3):317-323.
[17]Xu Hui, Zong Zhiping. 2014. Analysis on characteristics of thermal vertical strunture evoluyion during the transition of precipitation type in winter[J]. Plateau Meteor, 33(5):1272-1280. DOI:10.7522/j.issn.1000-0534.2013.00118.<br/>徐辉, 宗志平. 2014.一次降水相态转换过程中温度垂直结构特征分析[J].高原气象, 33(5):1272-1280.
[18]Wang Hongxia, Miao Aimei, Dong Chunqing, et al. 2013. Cause analysis on the phase transformation of precipitation in Shanxi in spring[J]. Plateau Meteor, 32(6):1787-1794. DOI:10.7522/j.issn.1000-0534.2012.00165.<br/>王洪霞, 苗爱梅, 董春卿, 等. 2013.山西一次春季降水过程相态变化的成因分析[J].高原气象, 32(6):1787-1794.
