A Numerical Study on Effects of Land-Surface Heterogeneity from ‘Combined Approach’ on Atmospheric Process Part II: Coupling-Model Simulations

1.IntroductionInthecompanionPaper(hereafterreferredtoas299),wecombinedthemosaicapproachandtheanalyticaltypeofstatistical--dynamicalapproach,andproPOsedaacombinedapProach",whichcouldrepresentbothinterpatchvariabilityandintrapatchvariabilityaswellascomputationallycostless.Aftertheheterogeneityoftheroughnesslengthic(or/andzeroplanedisplacementheightd,)isconsideredbythecombinedapproachinBiosphere/AtmosphereTransferSchemeVersionie(BATSie)(Dickinsonetal.,1993),expressions,suchasdragcoefficienta…

A Numerical Study on Effects of Land-Surface Heterogeneity from' Combined Approach' on Atmospheric Process Part II: Coupling-Model Simulations

Two land surface schemes, one the standard Biosphere / Atmosphere Transfer Scheme Version ie (BOZ) and the other B1Z based on B0Z and heterogeneously-treated by' combined approach' , were co "pled to the meso-scale model MM4, respectively. Through the calculations of equations from the companion paper, parameters representing land surface heterogeneity and suitable for the coupling models were found out. Three cases were simulated for heavy rainfalls during 36 hours, and the sensitivity of short-term weather modeling to the land surface heterogeneity was tested. Through the analysis of the simulations of the three heavy rainfalls, it was demonstrated that BIZ, compared with BOZ, could more realistically reflect the features of the land surface heterogeneity, therefore could more realistically reproduce the circulation and precipitation amount in the heavy rainfall processes of the three cases. This shows that even short-term weather is sensitive to the land surface heterogeneity, which is more obvious with time passing, and whose influence is more pronounced in the lower layer and gradually extends to the middle and upper layer. Through the analysis of these simulations with BlZ, it is suggested that the bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the s ig nificantly-heterogeneous land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to influence the development of the low-level jets and precipitation. And also, the complexity of the land-atmosphere interaction was shown in these simulations.