地表太阳辐射参数化改进在高原山区WRF模式降水模拟中的应用  

Improvement of surface solar radiation effect parameterization and its application in WRF precipitation simulation in plateau mountainous areas

作　　者：覃建明 刘家辉 乔泽宇 倪广恒[1] QIN Jianming;LIU Jiahui;QIAo Zeyu;NI Guangheng(State Key Laboratory of Hydroscience and Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学水沙科学与水利水电工程国家重点实验室,北京100084

出　　处：《清华大学学报（自然科学版）》2023年第12期1935-1945,共11页Journal of Tsinghua University(Science and Technology)

基　　金：国家重点研发计划项目(2018YFA0606002)。

摘　　要：区域气候模式对高原降水模拟存在系统性高估。该文从热力学角度考虑了局地(小尺度)地形对陆气过程的影响,以提高区域气候模式高原降水模拟能力。通过在天气研究与预报(weather research and forecasting, WRF)模式陆面过程模块耦合地形热力效应方案,将二维地形太阳辐射方案改进为三维地形太阳辐射方案,根据山区太阳辐射理论对太阳辐射直射、辐射散射、地形反射过程进行改进,得到改进方案;基于改进方案在亚东河谷开展高分辨率WRF模式降水模拟研究。结果表明:采用改进方案模拟的太阳辐射、降水结果与实测结果更接近,能够降低河谷降水高估的现象。改进方案能够体现出更多地形变化对地表辐射分布的影响:日间,山体坡面由于接收更多辐射得到加热(0.09~0.20℃),产生上升气流,在坡面形成更强上坡风(0.02~0.08 m/s),将河谷水汽携带到坡面以上,水汽在坡面以上区域爬升并形成降水,导致河谷区域降水减少(-4.54~-3.34 mm)、坡面以上区域降水增多(0.59~2.82 mm)。该研究对提高区域气候模式对山区降水的模拟效果具有重要意义。[Objective] The parameterization schemes for the surface solar radiation effect in the climate model primarily include the plane-parallel radiative transfer scheme, two-dimensional(2-D) solar radiation effect scheme, and three-dimensional(3-D) solar radiation effect scheme. Because the plane-parallel radiative transfer scheme assumes a flat topography, it cannot ascertain the impact of terrain on radiation, which results in systematic biases in simulating the land surface processes of the climate model. The 2-D scheme only considers the impact of the terrain slope and aspect on the solar incident angle. However, it overestimates the surface radiation during early morning and late afternoon, leading to systematic biases in simulating precipitation over mountainous areas. In contrast, the 3-D scheme is based on the solid physical foundation of the mountain radiation theory, which considers the radiation impact of 3-D structures along the sub-grid terrain on the surface radiation. The weather research and forecasting(WRF) model incorporating the 2-D scheme in simulating land surface processes also encounters problems related to the precipitation overestimation and cold bias over the Tibetan Plateau. [Methods] This study coupled the WRF model with the 3-D scheme to accurately represent surface radiation processes over complex terrains such as the Tibetan Plateau, thus improving the model performance in simulating surface energy balance and precipitation. Based on the mountain radiation theory, the WRF model was incorporated with the following three types of incoming solar radiation: the solar radiation flux, diffuse radiation flux, and solar radiation flux reflected by the surrounding terrains. The influence of local(small-scale) topography on the land-atmosphere process was considered from the perspective of thermodynamics to improve the simulation ability of a regional climate model for precipitation over the plateau. Accordingly, a high-resolution WRF simulation study was conducted in the Yadong Valley, located in

关 键 词：高海拔山区 复杂地形 参数化方案 太阳辐射 天气研究与预报(WRF)模式 

分 类 号：P40[天文地球—大气科学及气象学]