文章摘要
2021年2月黄河中下游两次暴雪过程中的相态转换及成因分析
Analysis on transition of precipitation type and causes of two snowstorms over the middle and lower streams of the Yellow River in February 2021
投稿时间:2021-11-11  修订日期:2022-01-27
DOI:
中文关键词: 黄河中下游,暴雪过程,降水转换,形成机理
英文关键词: the middle and lower streams of the Yellow River  heavy snowfall  transition of precipitation type  formation mechanism
基金项目:国家自然科学基金项目面上项目(41975055);山东省预报员专项(SDYBY2018-05)
作者单位
郑丽娜 济南市气象局 
李恬 济南市气象局 
孙骞 济南市气象局 
田雪珊 济南市气象局 
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中文摘要:
   利用常规高空资料、地面加密自动站、双偏振多普勒雷达、微波辐射计、ERA5再分析资料及GPS-MET等多源观测资料,分析了2021年2月下旬黄河中下游两次暴雪过程的相态演变及形成机理。结果表明:两次过程的大尺度影响系统基本一致,只是影响系统的强度和位置不同导致两次过程存在些许差异。两次过程前期均表现为同一时刻雨、雪与雨夹雪三种相态共存,过程后期,过程Ⅰ中存在降水相态逆转(由雨转雪再转雨),过程Ⅱ中只存在雨转雪的相态转换。在太行山以西的山区,即使1000 hPa与925 hPa温度在2℃以上,只要地面2 m气温低于0.5℃,降水相态仍以雪为主;在平原地区,当2 m气温在1~2℃时,降水相态为雨或雨夹雪,在0~1℃时,则为雪与雨夹雪并存,低于0℃时,降水相态为雪。降水相态为雪时,反射率因子强度多在30 dBZ或以下,差分反射率(ZDR)<1 dB,相关系数(CC)接近1。过程Ⅰ中出现的相态逆转是因为江淮气旋形成后倒槽北伸,倒槽顶端的偏东风携带海上暖湿空气造成近地层升温造成的。两次过程均产生了较常年明显偏多的降水量,是因为有充沛的水汽供应,降水区的水汽含量高出同期平均水汽含量近4倍多;对流层内存在不稳定层,在地面中尺度辐合线与中尺度低压的触发下,导致了暴雪过程的发生。
英文摘要:
   The phase evolution and formation mechanism of two snowstorm processes in the middle and lower streams of the Yellow River in late February 2021 are analyzed by using multi-source observation data such as conventional high-altitude data, ground encrypted automatic station, dual-polarization Doppler radar, microwave radiometer, ERA5 reanalysis data and GPS-MET data. The results showed that the large scale influence systems of the two processes are basically the same, but the intensity and position of the influence systems are different, leading to some differences between the two processes. In the early stage of the two processes, three phases of rain, snow and sleet coexist at the same time. In the late stage, there is a phase reversal of precipitation in process Ⅰ( rain-snow-rain ), while in process Ⅱ, there is only a phase transition from rain to snow. In the mountains west of Taihang Mountain, even if the temperature of 1000 hPa and 925 hPa is above 2℃, as long as the air temperature at 2 m is below 0.5℃, the precipitation phase is mainly snow. In plain area, when the temperature of 2 m is 1 ~ 2℃, the precipitation phase is rain or sleet; when the temperature is 0 ~ 1℃, the precipitation phase is snow and sleet coexist; when the temperature is below 0℃, the precipitation phase is snow. When precipitation phase is snow, the intensity of reflectance factor is mostly 30 dBZ or less, the difference reflectance (ZDR) is less than 1 dB, and the correlation coefficient (CC) is close to 1. Phase reversal in process I was caused by the north extension of the inverted trough after the formation of the Jianghuai cyclone, and the warm and humid air carried by the easterly wind at the top of the inverted trough caused the warming of the surface layer. There was abundant water vapor supply in the two processes, and the water vapor content in the rainfall area was more than 4 times higher than the average water vapor content in the same period. There was an unstable layer in the troposphere, which was triggered by the mesoscale convergence line and mesoscale low pressure on the surface, leading to the occurrence of these two precipitation processes with convective nature.
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