不同陆面方案对降水模拟的影响

Influence of land surface schemes on precipitation simulation

基于区域气候模式RegCM4.0(Regional Climate Model 4.0),分别选取BATS(Biosphere Atmosphere Transfer Scheme)和CLM(Community Land Model)陆面方案,对2001—2005年中国的气候状况进行模拟,并将模拟结果与CRU(Climatic Research Unit)及GPCP(Global Precipitation Climatology Project)降水资料进行对比,研究不同陆面方案对降水模拟的影响。结果表明:在两种陆面方案下,区域气候模式均较合理地模拟出了中国降水的空间分布、时间变化;模拟降水对陆面方案敏感,RegCM_BATS总体上表现为正偏差,在东北区域的模拟偏差较大;RegCM_CLM表现为负偏差,在长江以南区域的模拟偏差较大;模拟结果的偏差在夏季较大,冬季较小;两模式模拟结果间的差异在空间上由东南向西北减少;两模式均较准确地模拟了不同强度降水出现频率的分布形势,总体上RegCM_CLM模拟低强度降水偏多;高强度降水偏少,而RegCM_BATS模拟低强度降水偏少,高强度降水偏多;不同陆面方案对地表蒸发量以及地表潜热通量模拟的差异是导致模拟降水差异的主要原因,夏季地表蒸发对降水的影响较冬季更强;水汽平流输送对两模式模拟降水差异的影响较小。

The influence of land surface schemes on precipitation simulation is examined through two muhiyear simu- lations of the China＇s climate during the period from 2001 to 2005. The Regional Climate Model （RegCM Version 4.0 ） coupled to the Biosphere-Atmosphere Transfer Scheme （BATS） and the Community Land Model （CLM） respec- tively is used for the climate simulation. The precipitation simulations are compared to two precipitation datasets Cli- mate Research Unit of University of East Anglia （CRU）, and Global Precipitation Climatology Project （GPCP）. The result shows that both spatial distribution and temporal variation of China＇s precipitation can be reasonably simulated by RegCM4.0 coupled to the two land surface schemes. However, the RegCM_BATS generally produces a positive bi- as in the simulated precipitation, while the opposite is true for the RegCM_CLM precipitation, indicating that precipi- tation simulation is sensitive to different land surface schemes. The largest positive bias is found in Northeast China for RegCM_BATS, and in the South of Yangtze River for RegCM CLM, the RegCM_CLM precipitation has the biggest negative bias. The simulation bias is large in summer months, and small in winters. The precipitation differences be- tween the two simulations decrease from Southeast to Northwest. Both RegCM_BATS and RegCM_CLM can well simu- late the precipitation frequency for different intensities. RegCM_CLM generally overestimates low intensity precipitati- on and underestimates high intensity precipitation. The opposite is true for RegCM_BATS. Differences in the modeled evaporation and latent heat flux with the two land surface schemes are the major causes of the precipitation difference between the two simulations. The influence of evaporation on precipitation simulation is larger during the summer months than that of winter months. While, the water vapor advection has an insignificant influence on precipitation simulation.