利用敦煌干旱区陆气相互作用外场加强观测试验数据， 分析了夏季干旱区边界层高度、 逆温层逆温强度以及频率密度的特征。结果表明， 虚位温垂直变化的极值可以确定对流边界层(CBL)、 稳定边界层(SBL)和残留层顶(RLT)的高度。夏季敦煌干旱区CBL、 SBL和RLT的高度平均为2.09 km、 594 m和3.53 km， 三者逆温层强度(Δθv, zi)平均为0.084~0.088 K·(10 m)-1。CBL高度基本遵从均匀分布， SBL和RLT高度分别遵从显著的伽玛分布和极值分布， 三者的Δθv, zi均遵从显著的伽玛分布。CBL高度与Δθv, zi的联合频率密度在0.05≤Δθv, zi≤0.1 K·(10 m)-1的线状区域中最大， SBL高度与Δθv, zi的联合频率密度在SBL高度<1 km、 Δθv, zi=0.1 K·(10 m)-1和0.025 K·(10 m)-1附近的两区域中较大， RLT高度与Δθv, zi的联合频率密度则在RLT高度等于3\^5 km附近且Δθv, zi=0.11或Δθv, zi=0.06~0.08 K·(10 m)-1的区域中较大。
The height of the (CBL) in arid region was found to access 4 km in summer. Based on the intensified observational data for land-atmosphere interaction field experiment performed in a typical arid region, namely Dunhuang, Gansu Province, the characteristics of the atmospheric boundary, the inversion-layer intensity and its frequency density in arid region of Northwest China are studied using the statistical methods. The extreme value of vertical change of virtual potential temperature is used to determine the heights of convective boundary layer (CBL), stable boundary layer(SBL) and the top of residual layer(RLT). The results show that the averaged heights of CBL, SBL and RLT are 2.09 km, 594 m and 3.53 km, respectively, and their intensities (Δθv, zi) of inversion layers present obvious diurnal variations that is in 0.084~0.088 K (10 m)-1 on average. The heights of SBL and RLT satisfy very significant Gamma distribution and extreme-value distribution, respectively, both with maximal frequencies are located separately below 1 km height and near 3.8 km height while the height of CBL shows a uniform distribution in the range of 0~4 km on the whole. All of the Δθv, zi of three obeys significant Gamma distribution. Joint frequent densities of the height and the Δθv, zi demonstrate that CBL tends to have Δθv, zi within [0.025, 0.1] K·(10 m)-1 regardless of how much CBL height is, SBL tends to have its height less than 1 km and its Δθv, zi neighboring on 0.1 K·(10 m)-1 and 0.025 K·(10 m)-1, and RLT tends to have its heights in the vicinity of 3.5 km and its Δθv, zi equal to 0.1 or 0.06~0.08 K·(10 m)-1.
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