张璐,黄倩,张宏昇,张强,田红瑛. 2021. 干湿地表的湍流特征及其对深对流影响的大涡模拟[J]. 气象学报, 79(4):659-673, doi:10.11676/qxxb2021.037
干湿地表的湍流特征及其对深对流影响的大涡模拟
Large eddy simulation of turbulence effects on deep-convection triggering over dry and wet surfaces
投稿时间:2020-06-29  修订日期:2021-04-09
DOI:10.11676/qxxb2021.037
中文关键词:  干、湿地表  初始温、湿度廓线  湍流特征  深对流  大涡模拟
英文关键词:Wet and dry surfaces  Initial thermal and humidity profiles  Characteristics of turbulence  Deep convection  Large eddy simulation
基金项目:国家自然科学基金项目(41775013、41875046、91837209)、第二次青藏高原综合科学考察项目(2019QZKK0105)、新疆维吾尔自治区高层次(柔性)人才引进项目(2018)
作者单位E-mail
张璐 兰州大学大气科学学院半干旱气候变化教育部重点实验室兰州730000
北京大学物理学院大气与海洋科学系气候与海-气实验室北京100871 
 
黄倩 兰州大学大气科学学院半干旱气候变化教育部重点实验室兰州730000 qianhuang@lzu.edu.cn 
张宏昇 北京大学物理学院大气与海洋科学系气候与海-气实验室北京100871  
张强 中国气象局兰州干旱气象研究所/甘肃省干旱气候变化与减灾重点实验室/中国气象局干旱气候变化与减灾重点开放实验室兰州730020
甘肃省气象局兰州730020 
 
田红瑛 兰州大学大气科学学院半干旱气候变化教育部重点实验室兰州730000  
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中文摘要:
      利用大涡模式模拟了对流边界层结构演变以及深对流触发过程。通过改变鲍恩比的敏感性试验研究不同大气初始状况下湿润和干旱下垫面湍流特征及其对深对流触发过程的影响。结果表明:干旱下垫面的混合层干而暖,厚度较大;湿润下垫面相反。由于地表感热通量对热力湍流形成的作用更大,干旱下垫面上湍流混合和夹卷作用更强,使得水汽和相当位温在边界层内分布更均一,而在边界层顶有较大的负扰动;干旱下垫面上对流强度较湿润下垫面大,但均表现为泡状对流,水平方向上呈网状结构。不同下垫面上深对流的发生与大气初始状况有关,当初始时刻1—3 km的逆温强度较弱时(0.15 K/(100 m)),边界层内湍流迅速发展,深对流首先在干旱下垫面发生,但因对流有效位能较小,云层厚度小于湿润下垫面。当1—3 km的逆温强度增加到0.55 K/(100 m)时,云层形成时间较晚,云层厚度明显减小,仅当边界层顶的比湿较大时,有深对流发生,但仍首先发生在干旱下垫面,考虑贯穿对流在边界层顶引起的较强冷却作用,云层厚度大于湿润下垫面。
英文摘要:
      Using the Met Office large eddy model (LEM), a series of boundary-layer convection and deep convection experiments are performed to examine the characteristics of turbulence and deep convection triggering mechanism under different initial potential temperature and specific humidity conditions over wet and dry surfaces. Model results indicate that the mixed layer is warmer and drier over dry surface with a larger depth, and the opposite is true over wet surface. Because the surface sensible heat flux is more efficient in the formation of thermal turbulence, turbulent mixing and entrainment are stronger over dry surface, making the water vapor mixing ratio and equivalent potential temperature more uniform within the convective boundary layer (CBL) but a greater negative disturbance at the top of the CBL. The convection structure is the same as the bubble-like convection with a horizontal net-like structure over both wet and dry surfaces, but more vigorous over dry surface. The triggering of deep convection over different surfaces varies dramatically with the initial atmospheric condition. With weak atmospheric inversion (0.15 K/(100 m)) in the 1-3 km layer, deep convection first occurs over dry surface, but the accompanied clouds are thinner than those over wet surface because of the smaller convective available potential energy. Increasing the inversion intensity in the 1-3 km to 0.55 K/(100 m) not only delays the formation of clouds, but also decreases the cloud thickness. Only when combined with high initial specific humidity at the top of the CBL, can deep convections occur, also first over dry surface, and the associated clouds are thicker as a result of a significant cooling of the CBL top.
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