非均匀地表类型有效粗糙度的计算和特征分析

摘要

A new method is proposed for the effective roughness length (ERL) in heterogeneous terrain basedon the principle of equalization of momentum or heat fluxes calculated by the drag coefficient parameter-ization scheme used in the ECMWF numerical model. Compared with the area-weighted logarithmicallyaveraged ERL (drag coefficient), the newly calculated ERL (drag coefficient) is about 40% (16%) largerwith a roughness step of 2.3. These differences reach their maximum values when the ratio of smooth torough surface is 60% to 40%. Since the determination by this method is not sensitive to the atmosphericstratification, it is suitable for use in climate models.%利用湍流通量相等原理和ECMWF的总体湍流输送系数参数化方案,研究了气候数值模式中非均匀地表类型的有效粗糙度计算问题.结果表明,当存在两种地表类型且粗糙变率为2.3时,有效粗糙度比通常采用的对数加权平均值大40%左右,相应的总体湍流输送系数大16%左右,光滑地表类型和粗糙地表类型所占面积百分比分别为60%和40%时,有效粗糙度及相应的总体湍流输送系数和相应的对数加权平均值之差最大,并且有效粗糙度对大气层结不敏感,因而在气候模式中有实用价值.