中文摘要：

将任一中尺度区域的平均瞬间径流率考虑为区域平均降水量和地表土壤层水分渗透量的余项。根据降水量在地理空间上分布的实测资料拟合其空间概率密度函数（PDF）,并结合土壤入渗物理过程的数学描述及其经验公式,精确估计出地表土壤渗透率及其空间分布,由此建立区域地表径流率的统计-动力学估计方案。换言之,区域内地表产流率可视为区域平均降水量与区域平均的土壤下渗量之差值,而区域内土壤的平均下渗量又可分为非饱和区和饱和区两部分的下渗量来分别计算。就陆面水分循环的物理过程而言,地表入渗现象是在一定的下垫面特性基础上,由一定的水分供应源而形成的。根据大气降水向地表层输送水分的物理过程,在满足植被表层覆盖需水（截流水）和地表层土壤入渗水基础上,多余的降水量才会形成地表径流。因此,推求地表产流率的主要关键在于地表土壤层需水量。为此本文根据土壤水分通量方程推导出水分入渗公式。又从描述土壤水分和降水的空间PDF出发,推导出非均匀土壤含水量及降水气候强迫所形成的次网格尺度区域平均径流率计算公式。利用长江三角洲地区1996年降水量和土壤特性等实测资料建立区域平均地表径流率的估计公式,并对其影响因素进行敏感性试验。结果表明,该方法与用Mosaic方法计算的区域径流率（或产流率）结果十分接近。由此可见,该文提出的降水气候强迫下非均匀地表区域平均径流的这种统计-动力参数化方案,具有相当的可靠性与可行性。

英文摘要：

Based on the consideration of regional mean runoff as the difference between regional mean rainfall and infiltrations of surface soil layer over an arbitrary mesoscale region, a parameterization scheme for regional mean runoff over heterogeneous land surface under climatic rainfall forcing is presented. Surface soil infiltration and its spatial distribution for an arbitrary region can be accurately estimated with the fitted spatial probability density function （PDF） from the regional rainfall observations, and the mathematical description of soil water infiltration processes and its experimental expressions, and based on those theoretical and experimental expressions, a statistieal-dynamic estimation scheme for regional mean runoff was developed. In other words, regional mean runoff may be considered as the difference values between mean rainfall and infiltrations over a given heterogeneous land surface region, and the mean infiltration for the region may be calculated from two parts of infiltrations for saturation and non-saturation areas. In the physical process for water cycle of land surface, the soil water infiltrations occur where there is certain water resource over a given underlying surface. When the atmospheric precipitation falls on the ground surface, a portion of rain waters is first trapped by surface plant cover and adsorbed by surface soil, and then the residual portion of rain waters may form the surface runoff. This suggests that the key for estimating soil surface runoff is to estimate the storage of soil waters. A parameterization scheme is developed by deriving the water infiltration expression from the soil water flux equation, and by deriving the heterogeneous soil water content and the regional mean runoff expression over heterogeneous land surface under climatic rainfall forcing from the PDFs of describing spatial distributions of soil water and rainfall, respectively. The reliability and feasibility of the parameter scheme expression for regional mean runoff are confirmed by comparin