西北干旱区夏季大气边界层结构及其陆面过程特征  

A study on atmospheric boundary layer structure on a clear day in the arid region in northwest China

作　　者：张强[1] 王胜[1] 

机构地区：[1]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

出　　处：《气象学报》2008年第4期599-608,共10页Acta Meteorologica Sinica

基　　金：国家自然科学基金项目(40575006);国家重点基础研究发展规划项目(G1998040906)

摘　　要：在中国西北干旱区影响大气边界层形成和发展的气候环境和大气环流背景都具有一定特殊性。文中用外场观测试验资料,分析了位于西北干旱区的敦煌荒漠夏季大气边界层气象要素结构特征,发现该地区无论白天的对流边界层还是夜间的稳定边界层均比一般地区更深厚。在夏季晴天,夜间稳定边界层厚度超过900m,最厚可以达到1750m,其上的残余层一般能达到4000m左右的高度;白天混合层最高达3700m,混合层顶的逆温层顶盖的厚度大约450m,甚至更厚,对流边界层厚度能够超过4000m,对流边界层进入残余层后发展十分迅速。研究表明,白天深厚的对流边界层是夜间保持清晰而深厚的残余混合层的先决条件,夜间深厚的残余混合层又为白天对流边界层的发展提供了一个非常有利的热力环境条件。该地区经常性出现连续性晴天使得大气残余层的累积效应得以较长时间持续发展,创造了比较有利于大气对流边界层发展的大气热力环境条件。同时,该地区陆面过程和近地层大气运动特征也为这种独特的大气热力边界层结构提供了较好的支持。就该地区发展超厚大气对流边界层的物理机理而言,地表显著增温是强有力的外部热力强迫条件,近地层强感热通量提供了较充足的能量条件,较大的对流运动和湍流运动的速度是必要的运动学条件,大气残余层的累积效应提供了有利的热力环境条件。The climate environment and atmospheric circulation background affecting the formation and development of atmospheric boundary layer are relatively particular in Northwest China. Vertical structural characters of main physical factors in the arid desert of Northwest China in summer are analyzed based on the field intensive observation data in Dunhuang during May June 2000. Whether the convection boundary layer（CBL） in the daytime or the stable boundary layer （SBL） in the nighttime in this area are thicker than those in other areas. In the nighttime of a summer clear sky day, the depth of SBL generally exceeds 900 m and its maximum may reach 1750 m. The top of the residual layer （RL） atop the SBL can touch a height of about 4000 m. In the daytime, the CBL develops rapidly after entering into the RL, and its depth exceeds 4000 m. The results show that a deep CBL in the daytime is a precondition for maintaining a deep RL in the nighttime. Meanwhile, a deep RL in the nighttime provides a favorable thermal condition for the development of the CBL in the daytime. The frequent continuous clear days in this area make it possible for the accumulated effect of RL to build up persistently, which creates a favorable thermal condition for the development of atmospheric CBL. At the same time, the characteristics of land surface processes and atmospheric motion in the surface layer in this area also provide positive support for the particularly deep structure of atmospheric thermal boundary layer. In regard to formation mechanism for the deep CBL, the dramatic increase in surface temperature in the daytime is a powerful external thermal forcing, the strong sensible heat flux in surface layer is a sufficient energy source, larger convection and turbulent motion velocities are a necessary kinetic condition, and the accumulation effect of RL provides a favorable thermal environment.

关 键 词：西北干旱区 夏季晴天 大气边界层厚度 垂直结构 陆面过程 

分 类 号：P404[天文地球—大气科学及气象学]