地表粗糙度非均匀性对模式湍流通量计算的影响  

The Impact of Heterogeneity of Land Surface Roughness Length on Estimation of Turbulent Flux in Model

作　　者：陈斌[1] 徐祥德[1] 丁裕国[2] 施晓晖[1] 

机构地区：[1]中国气象科学研究院灾害天气国家重点实验室 [2]南京信息工程大学

出　　处：《高原气象》2010年第2期340-348,共9页Plateau Meteorology

基　　金：中日政府间JICA渠道技术合作项目"中日气象灾害合作研究中心";科技部国际合作项目(2007DFB20210);中国气象科学研究院基本科研业务费专项资金重点项目(2008Z006);灾害天气国家重点实验室自主研究项目(2008LASWZI04)共同资助

摘　　要：理论分析和数值试验结果表明,地表参量的不均匀性对网格区地表湍流通量的计算有重要影响。近中性大气层结条件下,次网格粗糙度长度的变差系数、网格平均粗糙度及参考高度的选取是影响网格湍流通量计算的主要因素,其中次网格粗糙度长度的变差系数对计算偏差起主要决定作用。实际计算表明,某些特定地区(如植被气候过渡带)粗糙度的地表非均匀性引起的计算相对误差可达40%以上,选取特定的参考高度能改善高网格湍流通量计算的效果。非中性大气层结条件下,由地表粗糙度不均匀性所致的平均风速、位温梯度以及近地层大气稳定度的次网格分布都对网格湍流通量(感热通量)计算产生影响,比较而言,相对误差大小对大气稳定度的次网格分布最为敏感。所以,在目前的数值模式中有必要进一步对湍流通量计算过程中由于地表不均匀性产生的计算偏差加以考虑。Based on the preliminary theoretically analysis,it is found that land surface heterogeneity plays an important role in the turbulent flux calculation in model.There is a discrepancy between the turbulent fluxes calculated by average parameters in model and the reality due to the land surface heterogeneity.The discrepancy may be decomposed into two parts,one is generated by the correlation between subgrid bulk transfer coefficient and land surface temperature or humidity,another is generated due to the non-linear relationship between surface roughness length and stability.The theoretic analysis and numerical results show that the subgrid variation of roughness length is the main factor that caused calculation error in the neutral atmosphere conditions.Although the magnitude of errors is determined by the variety coefficient of special distribution of roughness length,the grid area mean roughness length and the height of reference level,the former is the most important to determine the error magnitude.The relative error generated by the roughness heterogeneity could be more than 40% in some special cases. In stable or unstable atmosphere conditions,taking the sensible heat for example,the analysis showed that the discrepancy is correlated to the mean wind velocity,potential temperature difference between land surface and reference levels and the subgrid atmosphere stability distribution,which is the most sensitive to fluxes.In the case of the occurrence of stability and no-stablity atmosphere at the same time in one grid cell,turbulent fluxed estimation may be several times compared to the result calculated by mean parameters.The above analysis results show that it is necessary to make a further consideration for the calculation of the turbulent fluxes in the numerical models.

关 键 词：地表不均匀性 次网格尺度 网格湍流通量 粗糙度长度 

分 类 号：P404[天文地球—大气科学及气象学]