降水对陆面蒸发过程的影响及其参数化改进研究

The accurate description of hydrological processes is the key to improve land surface simulation capability. Precipitation will cause a complex variation of air-vegetation-soil interaction in hydrological processes and so,the parameterization reality and rationality on such processes affect the capability of land surface model greatly. Based on the Community Land Model(CLM), the study on evaporation processes with the influence of precipitation are implemented by the theoretical analyzing, numerical fitting, numerical modeling and etc. The rainfall intensity and interception residual will be introduced into the canopy interception parameterization addition to precipitation and leaf-stem area index(LAI). The global scale evapotranspiration model based on ecosystem mechanism(PT-FI) will be applied to improve the evaporation calculation of canopy interception. The ground surface evaporation under heterogeneous runoff will be recalculated by a new designed scheme of thin water layer. The improved CLM will be coupled into a regional climate model(RegCM) for further modeling validation. The numerical modeling experiment scheme of off-line running of CLM and coupled running of atmosphere-land model in East Asia during summer monsoon will be designed and implemented. The purpose of the former off-line modeling is to evaluate the response of land hydrological processes to precipitation forcing, while the later coupled modeling aims at estimating the impaction of air-land interaction on the climate simulation capability with the influence of precipitation. The results drawn in this study have both the great importance on theoretical improvement of land processes parameterization and the application significance in improving the simulation capability of land surface model(LSM) and air-land interaction.

水文过程的准确刻画对提高陆面模拟能力具有重要作用，降水条件下植被和地表的水文功能较为复杂，对该过程参数化的真实性和合理程度成为制约陆面模式性能的关键。本项目基于当前广泛应用的通用陆面模式CLM，通过理论分析、数值拟合和模拟试验等方法，研究降水对陆面蒸发过程的影响机制，建立包含雨强和截留残余的冠层截留模型，建立基于生态系统蒸散模型PT-FI的冠层蒸发方案，研究和设计"薄水膜"模型解决非均匀径流影响下的表层蒸发问题，以此改进降水条件下蒸发过程参数化方案。将改进的陆面过程CLM引入区域气候模式RegCM，针对东亚地区夏季风期分别进行陆面离线模拟试验和陆气耦合模拟试验，前者旨在检验降水单向强迫下陆面过程模拟性能的改进效果，后者检验降水条件下陆气相互作用对气候模拟能力的影响。项目研究成果是对陆面过程参数化理论的重要完善和创新，对提高陆面水文过程模拟能力和改进陆气相互作用关系具有应用意义。

降水条件下植被和地表的水文功能较为复杂，对该过程参数化的真实性和合理程度成为制约陆面模式性能的关键。本项目基于通用陆面模式 CLM，通过理论分析、 数值拟合和模拟试验等方法，研究降水对陆面蒸发过程的影响机制，分析了不同降水强度下地面蒸发差异，提出了“薄水膜”地表蒸发方案，能够显著增强西南地区季风期的地表蒸发通量和潜热通量，同时削弱感热通量，对非季风期的模拟效果也具有一定的改进。结合地形坡度影响，在模式中设计引进了圣维南扩散波模型，合理考虑地形坡度对地表径流的汇流作用，通过坡面坡降和摩擦坡降控制回水效应，实现了地表径流水量的平流再分配，改进了地形复杂地区模式地表径流的模拟；考虑地表非均匀性，基于史密斯-帕兰格（1978）提出的经典入渗公式及王政友经过大量野外试验提出的入渗经验模型，引入考虑雨强影响的累积渗透方案，该方案在雨强较大时和降雨较多的夏秋季能够显著地削弱渗透、提高地表径流以及降低土壤湿度，经试验设计作为新的入渗模型，改进了模式陆面土壤下渗和降水再分配问题。基于模式现有冠层方案，研究提出了冠层拦截参数优化和考虑风速影响的冠层蒸发改进方案，并用于全球、中国区和云南地区等不同尺度蒸散过程模拟分析研究。将改进的陆面过程 CLM 引入区域气候模式 RegCM，针对东部地区、云南等典型区域分别进行陆面离线模拟试验和陆气耦合模拟试验，前者旨在检验降水单向强迫下陆面过程模拟性能的改进效果，后者检验降水条件下陆气相互作用对气候模拟能力的影响。项目研究成果是对陆面过程参数化理论的重要完善和创新，对提高陆面水文过程模拟能力和改进陆气相互作用关系具有应用意义。