干旱区生态环境知识资源中心(Arid): 干旱区夏季晴空期超厚对流边界层发展的能量机制

Arid

	干旱区夏季晴空期超厚对流边界层发展的能量机制
其他题名	The energy mechanism controlling the continuous development of a super-thick atmospheric convective boundary layer during continuous summer sunny periods in an arid area
	张强; 乔梁; 岳平; 李岩瑛
来源期刊	科学通报
ISSN	0023-074X
出版年	2019
卷号	64 期号:15 页码:1637-1650
中文摘要	在全球干旱区,因其特殊的气候环境背景,夏季晴天常常会出现其他地区少见的超厚对流大气边界层(superthick convective boundary layer, SCBL),这种特殊的边界层结构具有重要的天气气候意义,但目前对这种超厚对流边界层发展机制理解十分有限.这既制约了大气数值模式中针对这种超厚对流边界层的参数化改进,也限制了超厚对流边界层与天气气候背景相互作用的科学认识.通过选取我国西北干旱区敦煌荒漠戈壁为代表性研究区,利用以往在该区域开展的陆-气相互作用观测试验资料及长期业务探空观测资料,从大气边界层发展的能量机制出发,对该地区出现的超厚对流边界层的发展过程进行分析.分析表明:从日际尺度看在持续晴空期即使在白天地表感热通量日积分值不变甚至减弱的情况下,大气对流边界层(convective boundary layer, CBL)的日最大厚度仍然表现为逐日持续增高的特点,且地表感热提供的能量无法平衡对流边界层发展所需要吸收的能量.主要原因是深厚的近中性残余层(residual layer, RL)在对流边界层发展过程中发挥了重要作用,通过夹卷过程从残余层进入对流边界层的夹卷能量是对流边界层逐日持续发展的关键能量补充.在夏季连续晴空期,对流边界层与残余层之间会形成逐日循环增长机制,使干旱区夏季发展出超厚对流大气边界层.
英文摘要	In the arid regions of the world, due to the specific climatic and environmental background, a super-thick convective boundary layer (SCBL) often develops on sunny days in summer, whereas such phenomena rarely occur in other areas. This special boundary layer structure has an important synoptic and climatic significance, but there have been few studies of its development mechanism in arid areas, which greatly restricts the parametric improvement of the SCBL and our understanding of the interaction between weather and climate processes. This study was conducted in Dunhuang, which is located in the hinterland of northwest China. Based on data obtained from land-air interaction experiments and long-term operational sounding observations in this region, the energy mechanism controlling the development of the CBL and the developmental process of the SCBL were systematically analyzed. In arid northwest China, it is possible that the thickness of the CBL can extend to over 3 km for most of the year, except winter. Even in the early summer, when there is little rain and strong solar radiation, the thickness of the CBL may reach an extreme state of 5.4 km. The thickness of the CBL at this time is higher than that observed in midsummer, when there is slightly more precipitation in this area. This is basically consistent with the extreme thickness of the CBL recently discovered in the Sahara Desert in Africa. In the general mechanism that controls the development of the CBL, there is a close relationship between the development of the CBL and the sensible heat flux of the surface. However, the correlation between the thickness of the CBL and the surface sensible heat flux at the same time is not strong, whereas the correlation between the thickness of the CBL and the cumulative surface sensible heat flux is very strong. This indicates that the development of the CBL is the result of the continuous accumulation of the sensible heat flux on the surface, which is consistent with the energy mechanism controlling the CBL. Although the development of the CBL is closely related to the cumulative heating effect of the daytime surface sensible heat flux, the CBL would still continue to increase even if the integral value of the daytime surface sensible heat flux remained unchanged or even weakened during the continuous clear sky period. The energy provided through sensible heat does not fully explain the energy required to develop the CBL. This is mainly because the deep nearneutral residual layer (RL) background plays an important role in the development of the SCBL. The entrainment energy from the deep RL to the CBL is the key energy supply for the continuous development of the CBL. The sum of the entrainment energy and surface sensible heat energy coincides with the energy absorbed by the development of the SCBL. The reason for the occurrence of an SCBL in arid areas is not only the strong sensible heating in summer but also the persistent clear skies in such areas. In each continuous clear sky period, the positive feedback mechanism between the CBL and the RL will become operational. Under this mechanism, the daily maximum thickness of the CBL and the thickness of the RL will increase continuously. The thickness of the SCBL is generally over 3 km, although depths of over 5 km can develop through a cyclic growth mechanism during periods of strong surface heating. Otherwise, the thickness of the CBL can only reach 2-3 km in summer, and it is unlikely that an SCBL will develop. Strong sensible heating is the key trigger of the positive feedback cycle growth mechanism between the CBL and the RL, which explains why the SCBL phenomenon can only occur in dry areas, with intense surface heating in summer.
中文关键词	干旱地区 ; 超厚大气对流边界层 ; 地表感热累积效应 ; 夹卷能量 ; 正反馈循环增长
英文关键词	arid region super-thick atmospheric convective boundary layer surface sensible heat accumulation effect entrainment energy positive feedback cyclic growth
类型	Article
语种	中文
国家	中国
收录类别	CSCD
WOS类目	Engineering
WOS研究方向	Engineering
CSCD记录号	CSCD:6511621
来源机构	中国气象局兰州干旱气象研究所
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/239299
作者单位	张强, 中国气象局兰州干旱气象研究所;;甘肃省气象局, ;;, 兰州;;兰州, ;; 730020;;730020.; 乔梁, 中国气象局兰州干旱气象研究所;;兰州大学大气科学学院;;甘肃省气象信息与技术装备保障中心, ;;;;, 兰州;;兰州;;兰州, ;;;; 730020;;730000;;730020.; 岳平, 中国气象局兰州干旱气象研究所, 兰州, 甘肃 730020, 中国.; 李岩瑛, 甘肃省武威市气象局, 武威, 甘肃 733000, 中国.
推荐引用方式 GB/T 7714	张强,乔梁,岳平,等. 干旱区夏季晴空期超厚对流边界层发展的能量机制[J]. 中国气象局兰州干旱气象研究所,2019,64(15):1637-1650.
APA	张强,乔梁,岳平,&李岩瑛.(2019).干旱区夏季晴空期超厚对流边界层发展的能量机制.科学通报,64(15),1637-1650.
MLA	张强,et al."干旱区夏季晴空期超厚对流边界层发展的能量机制".科学通报 64.15(2019):1637-1650.