基于三种WRF陆面过程方案的东南亚毁林增温响应研究

选取东南亚中南半岛地区作为模拟区域,基于高分辨率的遥感观测森林变化数据和WRF数值模式,设计毁林前后的两种情景对旱季气候进行模拟,评估NoahMP、CLM和Noah mosaic三种陆面过程方案对热带毁林增温响应的模拟能力。结果表明,CLM方案在模拟历史气温中有着更好的表现,Noah mosaic方案的结果存在明显低估。然而,对比毁林前后两种情景的模拟结果,本文发现,只有采用了"次格网"方式的Noah mosaic方案较好地模拟出毁林增温响应特征。在格网尺度采用"主导类型"计算方式的NoahMP方案没有合理地呈现出森林损失对区域气候的影响。理论上,CLM模式在计算中同时考虑格网内所有植被类型,然而本文发现CLM方案在主导类型不变的格网对森林损失比例不敏感,而且对毁林反馈的模拟结果与NoahMP方案的结果更接近。据此推测,在WRF模式耦合CLM方案的过程中,格网内参数处理方式可能产生了错误,实际采用的是"主导类型"方式。在模拟土地覆盖类型变化对气候的影响时,本文推荐使用Noah mosaic方案。同时,建议在未来版本的WRF模型中修正目前耦合的CLM方案关于次格网方法的处理方式,提供更合理的水热通量模拟。

Simulated response of warming to Southeast Asian deforestation: insights from WRF simulations using three land surface models

Tropical forest has undergone rapid loss in the early 21st century,leading to warming effects on regional climate,mainly by means of changing evapotranspiration.Regional climate models are powerful tools for assessing the biophysical feedbacks of deforestation.As the key part of climate models,land surface schemes regulate the fluxes of heat and water vapour between land and atmosphere,which may greatly affect the pattern and magnitude of how changes in forest cover impact climate.In this study we investigate the deforestation-induced warming effect in the Southeast Asian Massif by employing three land surface schemes (NoahMP,CLM and Noah mosaic) in the Weather Research and Forecasting (WRF) model.We perform the analyses by designing two sets of experiments with comparative land-cover scenarios,derived from high-resolution forest cover change dataset during the local dry season.Model validations show that,regarding the magnitude,the CLM scheme is in good agreement with the observed surface air temperature,while the Noah mosaic scheme has the greatest negative biases.When comparing the results between the two scenarios,it is found that only the Noah mosaic scheme,which takes the sub-grid approach,reasonably reproduces the response of warming effect to deforestation.In contrast,the NoahMP scheme fails to accurately capture the deforestation-induced regional warming,due to the use of the dominant approach at grid level.The CLM,a scheme which theoretically considers all land cover types within girds,and thus should possess the capability to capture the climate feedbacks of deforestation,is less sensitive to forest loss in those grids where the dominant type remains unchanged,and presents a pattern of temperature change similar to that of the NoahMP scheme.Based on these results,we speculate that the CLM scheme takes the dominant approach instead of the all-type mosaic method when coupled into the WRF model.This work demonstrates that the Noah mosaic scheme could be temporally applied in simulating the climate feedbacks of land cover conversion.We suggest that the representations of sub-grid characteristics in the CLM scheme be modified in the next version of the WRF model.