三江源地区夏季-10℃层高度变化及云垂直结构特征

The -10 ℃ level height variation and cloud vertical structure characteristics over Headwaters of Three Rivers in summer

利用三江源地区沱沱河、玉树、达日3个探空站的探空资料对1999—2021年-10℃层高度时间变化趋势、突变时间进行了研究,同时对该地区2021年云出现频率和云垂直分布特征进行了研究,并探讨了-10℃层高度、云层垂直结构与降水的关系。结果表明:(1)近20 a来三江源地区夏季08时和20时的-10℃层高度平均值分别为7 014.1、7 201.6 m,并呈显著上升趋势。突变检验分析确定三江源地区夏季08时-10℃层高度出现突变是从2009年开始,20时出现突变是从2012年开始。(2)08时三江源地区夏季云层结构较为复杂,20时三江源地区夏季主要以单层云为主,6—8月平均出现频率分别为35%、42%、39%。从三江源地区夏季云顶高度、云底高度和云层厚度来看,7月云顶高度最低、云底高度最高、云层厚度最小。(3)三江源地区夏季-10℃层位于该地区云层中下部。产生降水时-10℃层高度主要集中在7 200~7 800 m,云层厚度在4 000~11 000 m。三江源地区夏季降水量与-10℃层高度、云顶高、云层厚之间存在显著的正相关,与云底高存在显著的负相关。-10℃层高度与云顶高度、云层厚度间存在显著的正相关;与云底高度间相关性不显著。

This paper analyzed the temporal variation trend and mutation time of the-10 ℃ layer height from 1999 to 2021 by using sounding data from three sounding stations in the Three Rivers Source area,including Tuotuo River,Yushu,and Dari.At the same time,the frequency and vertical distribution characteristics of clouds in the area in 2021 were analyzed,and the-10 ℃ layer height,cloud vertical structure,and their relationship with precipitation were explored.Results indicate that in the past 20 years,the height of the-10 ℃ level height in the Headwaters of Three Rivers shows a significant upward trend in summer.The average height of the-10 ℃ level height at 08∶00 BST and 20∶00 BST was 7 014.1 m and 7 201.6 m,respectively.The mutation test determines that the mutation time of the-10 ℃ level height at 08∶00 BST began in 2009,and the occurrence of a mutation at 20∶00 BST began in 2012.The summer cloud structure in the Headwaters of Three Rivers was more complex at 08∶00 BST,and the summer clouds were mainly single-layer clouds at 20∶00 BST,with an average occurrence frequency of 35%,42%,and 39%,respectively.From the perspective of cloud top height,cloud base height and cloud thickness in summer in the Headwaters of Three Rivers,the cloud top height was the lowest,the cloud base height was the highest,and the cloud thickness was the smallest in July.The summer-10 ℃ layer in the Headwaters of Three Rivers was located in the middle and lower part of the cloud cover in the area.When precipitation was generated,the height of the-10 ℃ level height was mainly concentrated between 7 200-7 800 m,and the cloud thickness was between 4 000-11 000 m.There was a significant positive correlation between precipitation and-10 ℃ level height,cloud top height and cloud thickness,and the significance test above 90% was passed.There was a significant negative correlation with cloud base height,and the significance test above 95% was passed.There was a significant positive correlation between the-10 ℃ level height and the height of the cloud top and the cloud thickness,but not with the cloud base height.