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 le (B0Z) and the other B1Z based on B0Z and heterogeneously- treated by 'combined approach', were coupled to the meso-scale model MM4, r espectively. Through the calculations of equations from the companion paper , parameters representing land surface heterogeneity and suitable for the c oupling models were found out. Three cases were simulated for heavy rainfal ls during 36 hours, and the sensitivity of short-term weather modeling to t he land surface heterogeneity was tested. Through the analysis of the simul ations df the three heavy rainfalls, it was demonstrated that B1Z, compared with B0Z, could more realistically reflect the features of the land surfac e heterogeneity, therefore could more realistically reproduce the circulati on and precipitation amount in the heavy rainfall processes of the three ca ses. This shows that even short-term weather is sensitive to the land surfa ce heterogeneity, which is more obvious with time passing, and whose influe nce is more pronounced in the lower layer and gradually extends to the midd le and upper layer. Through the analysis of these simulations with B1Z, it is suggested that th e bulk effect of smaller-scale fluxes (i.e., the momentum, water vapor and sensible heat fluxes) near the significantly-heterogeneous land surface is to change the larger-scale (i.e., meso-scale) circulation, and then to infl uence the development of the low-level jets and precipitation. And also, th e complexity of the land-atmosphere interaction was shown in these simulati ons.