Mosaic方法在非均匀下垫面上的适用性研究

在非均匀下垫面情况下, Mosaic方法是目前国际上广泛运用于模式中计算地表通量的方法.大量的研究表明, 下垫面的非均匀分布会引发局地环流, 非均匀分布的空间尺度较大时, 所引起的环流甚至可以达到海陆风的强度.这种环流的存在直接影响到次网格地表通量的计算.次网格地表非均匀分布, 尤其是大尺度模式中的次网格非均匀分布, 必将影响地表通量的计算.本文针对次网格地表非均匀问题, 设计了高分辨率的Mosaic试验和非均匀试验, 开展了不同背景风情况下的一系列数值试验, 以探讨这种影响的程度.结果表明, 在土壤湿度空间分布不均匀的情况下, 运用Mosaic方法计算得到的地表潜热通量偏小, 背景风较小的时候偏差较大, 背景风增强时偏差减小.

On Applicability of Mosaic Method under Heterogeneous Land Surface in Large-Scale Atmospheric Model

Under the heterogeneous land surface,the Mosaic method is the one which is widely used to calculate surface fluxes in land surface model.Many researches have shown that the heterogeneous land surface can induce local circulation,when the length scale of heterogeneity is enough large,the local circulation induced will even be as strong as land-see breezes.This kind of circulation directly influences the sub-grid surface fluxes.Sub-grid surface heterogeneity,especially that in large-scale atmospheric model,has important impact on calculation of surface fluxes.In this article,two groups of experiments,called Mosaic and heterogeneous respectively,are designed to investigate the sub-grid heterogeneity problem.Both groups include one group of regular-heterogeneous(chessboard) and two groups of irregular-heterogeneous experiments with different background wind.The results show that,under the sub-grid heterogeneous distribution of soil moisture,the surface latent heat flux calculated by Mosaic method is smaller than their true values.Moreover,with the background wind increasing,the deviation decreases.