The Application Simulation Of Land Surface Model CLM In Different Climate Models And The Improvement Test Of Its Canopy Interception Scheme

The Qian atmospheric forcing dataset is used to drive the Community Land Model,version 4.0 and 4.5(CLM4 and CLM4.5)in off-line simulation tests.Based on flux network(FLUXNET)data and reanalysis data provided by Climate Forecast System Reanalysis(CFSR)and Global Land Evaporation Amsterdam Model(GLEAM),the simulation results of CLM4.5 on the global evaporation of intercepted water from the vegetation canopy(Ec),vegetation transpiration(Et),evaporation of soil(Es)and latent heat flux are evaluated.Subsequently,the improvement in the simulation results of CLM4.5 compared with CLM4.0 is tested and analyzed.Secondly,the parameterization of canopy interception in CLM4.5 is improved by considering parameter estimation and physical structure.Next,the ability of RegCM4.5 using land surface scheme CLM4.5 to simulate the physical variables related to land surface state was assessed.Finally,the improvement effect of RegCM4.5 with CLM4.5 after improving land surface model is studied.The main conclusions are as follows:The simulated spatial distribution of Ec,Et and latent heat flux in CLM4.5 are closer to the reanalysis data than Es.The simulated annual means of Et,Es and latent heat flux in CLM4.5 are larger than the reanalysis data,but Ec is smaller.The spatial distribution of the simulation bias of latent heat flux in CLM4.5 is mainly determined by the bias distribution of Es.There is a significant difference in the simulation of Et,Es and latent heat flux between CLM4.5 and CLM4.0.These differences are mainly present near the equator and in the middle and high latitudes in the Northern Hemisphere.In general,compared with CLM4.0,the simulation bias of Et,Es,and latent heat flux have been reduced in CLM4.5,and the simulated means are more consistent with the reanalysis data.Although there is a significant improvement in the simulation of the spatial distribution of Et and Es in CLM4.5 compared with CLM4.0,the ability of CLM4.5 to simulate the spatial distribution of global latent heat flux shows little improvement relative to CLM4.0.Considering that different vegetation types have different intercept capacities for precipitation(denoted as SEN1),the simulation of the Ec has a very obvious improvement effect,which not only reduces the positive deviation of the model to the Ec simulation,but also significantly reduces the root mean square error(RMSE).SEN1's simulation of Et and latent heat flux also have a relatively obvious improvement effect,and the RMSE was also significantly reduced,and the simulated mean are more consistent with the reanalysis data.The effect of wind speed on canopy interception is considered on the basis of SEN1(denoted as SEN2).The Ec simulated by SEN2 is not only closer to the reanalysis data,but also further reduces the RMSE.However,the response of the Et and latent heat flux to this improvement is not obvious,and the improvement effect is basically consistent with that of SEN1.Some seasonal features of land surface temperature in summer and winter as well as its magnitude could be simulated well.The simulation of precipitation was sensitive to region and season.The model could,to a certain degree,simulate the seasonal migration of rainband in East China.The overall spatial distribution of the simulated soil moisture was better in winter than in summer.The simulation of latent heat flux was also better in winter.In summer,the latent heat flux bias mainly arose from surface evaporation bias in Northwest China,and it primarily arose from vegetation evapotranspiration bias in South China.In addition,the large latent heat flux bias in South China during summer was probably due to less precipitation generated in the model and poor representation of vegetation cover in this region.While the simulation results of the Ec in RegCM4.5 in Yunnan and its surrounding area is more than GLEAM reanalysis data,the Et is less than GLEAM reanalysis data.Simulation errors are mainly concentrated in wet season.After improving the canopy interception parameterization scheme in the land surface model CLM4.5 in RegCM4.5,the simulation errors of RegCM4.5 on Ec,Et and latent heat flux was significantly reduced,and the simulated sensible heat flux in wet season was also partially improved.The improvement of the empirical parameters of canopy interception precipitation can significantly affect the simulation ability of the land surface model CLM4.5 to simulate land surface climate,which is a very important parameterization scheme.In the simulation of regional climate,if the vegetation in the study area is relatively dense,the improved parameterization scheme can enhance the simulation effect of RegCM4.5 on land surface climate to a certain extent.