大气表面层与风沙现象相似参数的研究

本文从二维稳定不可压缩湍流方程出发，采用一种特殊的无量纲化过程─—尺度化方法，在大气表面层流动中选择出一组特定的内在参考量，将方程组无量纲化后，使各项前所出现的相似参数，具有可代表所在项数量级的特点，从而以定量方式估计出方程中各项的相对大小。研究结果推断，就实验室风洞中模拟风沙现象而言，流动Ｒｅ数的模拟既无可能又无必要，而近地层对数风速廓线，地表粗糙边界条件，湍流雷诺数和湍流强度的模拟，才是最关键的。     

双层非饱和地基中Rayleigh波的传播特性

研究了双层非饱和地基中Rayleigh波(以下简称R波)的传播特性问题。首先将迂曲度引入孔隙流体的渗流连续性方程,对三相孔隙介质波动方程进行修正,接着采用体波的势函数之和构建各相介质的势函数,并借助Helmholtz分解,以及考虑土层边界条件和层间连续性条件,建立了R波的弥散特征方程,分析了饱和度、迂曲度和上覆土层厚度等参数与波速和衰减性的关系。结果表明,R波波速随饱和度的增加而线性减小;在渗透系数中间区段,则随着固有渗透系数k的增大而增大;水力迂曲度τ_f对波速的影响主要体现在高频区段,而空气迂曲度τ_a的影响则非常有限;对于上软下硬地层,覆盖层厚度的增加将引起波速的减小,并逐渐趋于上覆土层本身的R波波速;且频率越高或表面层刚度越低,趋近速度越快。     

Parameterization of Heat Fluxes at Heterogeneous Surfaces by Integrating Satellite Measurements with Surface Layer and Atmospheric Boundary Layer Observations

The regional heat flux exchange between heterogeneous landscapes and the nearby surface layer (SL) is a key issue in the study of land-atmosphere interactions over arid areas such as the Heihe River basin in northwestern China and in high elevation areas such as the Tibetan Plateau. Based on analysis of the land surface heterogeneity and its effects on the overlying air flow, the use of SL observations, atmospheric boundary layer (ABL) observations, and satellite remote sensing (RS) measurements along with ...     

Study on Electrical Potential by Buried Source Electrode within the Horizontally Layered Half-space Model

The paper first studies the analytical expression of electrical potential by a point current source in a uniform half-space medium,and then focuses on the distribution of electrical potential in a horizontally layered half-space model by a point current source within the surface layer or the bottom layer.Finally,the electrical potential by a source electrode in any layer of a layered half-space model is presented.     

Simulated Impacts of Sulfate and Nitrate Aerosol Formation on Surface-Layer Ozone Concentrations in China

The authors quantify the impacts of sulfate and nitrate aerosol formation on surface-layer 03 concentrations over China using the one-way nested-grid capa- bility of the global three-dimensional Goddard Earth Ob- serving System chemical transport model （GEOS-Chem）. Chemical reactions associated with sulfate formation are simulated to generally increase 03 concentrations in China. Over the North China Plain （NCP） and the Si- chuan Basin （SCB）, where simulated sulfate concentra- tions are the largest, ozone concentrations show maximum increases in spring by 1.8 ppbv （3.2%） in the NCP and by 2.6 ppbv （3.7%） in the SCB. On the contrary, nitrate formation is simulated to reduce 03 concentrations by up to 1.0 ppbv in eastern China, with the largest reduc- tions of 1.0 ppbv （1.4%） in summer over the NCE Ac- counting for the formation of both sulfate and nitrate, the surface-layer O3 concentrations over a large fraction of eastern China are simulated to increase in winter, spring, and autumn, dominated by the impact of sulfate forma- tion, but to decrease in summer because of the dominant contribution from nitrate formation.     

Analysis on the Interaction between Turbulence and Secondary Circulation of the Surface Layer at Jinta Oasis in Summer

The kinetic energy variations of mean flow and turbulence at three levels in the surface layer were calculated by using eddy covariance data from observations at Jinta oasis in 2005 summer.It is found that when the mean horizontal flow was stronger,the turbulent kinetic energy was increased at all levels,as well as the downward mean wind at the middle level.Since the mean vertical flow on the top and bottom were both negligible at that time,there was a secondary circulation with convergence in the upper half and divergence in the lower half of the column.After consideration of energy conversion,it was found that the interaction between turbulence and the secondary circulation caused the intensification of each other.The interaction reflected positive feedback between turbulence and the vertical shear of the mean flow.Turbulent sensible and latent heat flux anomaly were also analyzed.The results show that in both daytime and at night,when the surface layer turbulence was intensified as a result of strengthened mean flow,the sensible heat flux was decreased while the latent heat flux was increased.Both anomalous fluxes contributed to the cold island effect and the moisture island effect of the oasis.