平涼一次暴雨前對流層頂異常特征分析

趙慧 馬鵬程 薛啟

摘要 利用NCEP/NCAR 1°×1°再分析資料和常規氣象觀測資料，以2016年7月18日出現在平涼的區域性暴雨為例，分析暴雨發生前對流層頂高度、溫度以及各高度的垂直速度、位渦、風場變化特征。結果表明，暴雨發生前4 d至前2 d對流層頂高度有明顯的下降，并于暴雨發生前2 d降至最低，最低為14.6 km，相反地，對流層頂溫度在暴雨發生前5 d至前2 d開始上升，并于暴雨發生前2 d升至最高，可達-65.6 ℃。對流層頂高度在暴雨發生前2 d的空間形變主要體現在南北方向上，高度的經向梯度變化比緯向梯度變化明顯;從緯向看，暴雨發生前2 d，2 PVU等位渦線可以向下發展至380 hPa附近，凹陷最明顯，即暴雨發生前2 d平涼地區對流層頂會出現折卷現象，暴雨發生當天，上升運動最強盛，最大垂直速度可達-0.3 Pa/s;對流層頂高度下降主要原因是由高層向下侵入的高位渦冷空氣及對流層頂折卷過程影響。以上結果表明，對流層頂附近異常信號對暴雨預測有較好的指示意義。

關鍵詞 對流層頂;暴雨前;位渦;風場;垂直速度;對流層頂高度;對流層頂溫度

中圖分類號 S 162? 文獻標識碼 A

文章編號 0517-6611（2021）19-0195-04

doi：10.3969/j.issn.0517-6611.2021.19.051

開放科學（資源服務）標識碼（OSID）：

Analysis of Abnormal Characteristics of Tropopause before a Rainstorm in Pingliang

ZHAO Hui，MA Peng-cheng，XUE Qi

（Pingliang Meteorological Bureau of Gansu Province，Pingliang，Gansu 744000）

Abstract By using the NCEP/NCAR global reanalysis data with the resolution of 1°×1° and conventional meteorological data，taking the regional rainstorm in Pingliang on July 18，2016 for example，the variation characteristics of tropopause height，temperature and the vertical velocity，potential vorticity and wind fields of each height were analyzed.The results showed that the tropopause height decreased significantly from 4 days to 2 days before the rainstorm，and decreased to the lowest（14.6 km） 2 days before of the rainstorm.Conversely，the tropopause temperature began to rise from 5 days to 2 days before the rainstorm，and rose to the highest 2d before the rainstorm，reaching -65.6 ℃.The tropopause height was mainly reflected in the north-south direction 2 days before the rainstorm，and the meridional gradient change was more significantly than that in the zonal direction.From the zonal direction，the 2 PVU potential vorticity line could be developed down to 380 hPa 2 days before the rainstorm，and the depression was the most obvious，that was，2 days before the rainstorm，the tropopause would appear folding in the Pingliang area，while the ascending movement was the strongest in the day of the rainstorm，and the maximum vertical speed could reach to -0.3 Pa/s.It was proposed that the lowering of the tropopause height was mainly due to the cold air from the high vorticity invaded by the upper layer and tropopause fold event process. Therefore，the characteristics of anomalous near the top of the tropopause could be applied to forecast rainstorm in Pingliang.

Key words Tropopause;Before rainstorm;Potential vorticity;Wind fields;Vertical velocity;Tropopause height;Tropopause temperature