文章摘要
杨成芳,刘畅,郭俊建,孟宪贵.山东相态逆转降雪天气的特征与预报[J].海洋气象学报,2017,37(1):73-83
山东相态逆转降雪天气的特征与预报
Statistical study of precipitation type reversal during snowy weather process in Shandong province
  
DOI:10.19513/j.cnki.issn2096-3599.2017.01.008
中文关键词: 降水相态  逆转  温度平流  温度日变化
英文关键词: precipitation type  reversal  temperature advection  diurnal variation of temperature
基金项目:国家自然科学基金项目(41475038);中国气象局关键技术集成与应用项目(CMAGJ2015M34);中国气象局预报员专项(CMAYBY2015-041);山东省气象局科研项目(2013sdqxz02,2015sdqx02)
作者单位
杨成芳,刘畅,郭俊建,孟宪贵 山东省气象台山东 济南 250031 
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中文摘要:
      采用高空和地面观测资料,对山东1999—2013年24次有相态逆转降雪过程的影响系统、出现时间、逆转前后的温度变化及各类系统逆转的天气形势特征进行了统计分析。结果表明:1)低槽冷锋、江淮气旋、黄河气旋和暖切变线可在山东产生降水相态逆转,而回流形势降雪不会产生逆转。2)山东降水相态逆转发生在11月—次年4月,以12月和1月居多,12月频率最高;有明显的日变化,14时前后最容易发生逆转,而23时—次日05时最少。3)雪转雨时最显著的特征为地面2 m气温升高,升温幅度多在1~2 ℃;850 hPa以下至地面的温度至少有1~2个层次升温。4)地面2 m气温对逆转的指示性最好,降雪时在0 ℃左右,略高于通常降雪阈值,最低为-1 ℃;其次为1 000 hPa,降雪时接近于0 ℃。5)对流层低层暖平流升温或温度日变化升温导致雪转雨,温度平流弱时温度日变化起主要作用。各类天气系统的逆转范围、时段等有明显差异。因此,对于降雪阈值附近的相态预报,需综合考虑低层温度平流和日变化两个因素,重点关注地面2 m气温能否升温,午后为关键时段。
英文摘要:
      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 return flow 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.
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