| The land surface is the main place for human activities and an important part of the climate system.The thermal,hydrological,and biological processes occurring on land and in the atmosphere are collectively referred to as land surface processes,where the energy exchange of thermal processes is critical for determining the hydrological cycle,boundary layer development,weather,and climate in ecosystems.Due to the complexity of the land surface,and the more complex dynamic and thermal characteristics shown by different time,there are still many unknown processes that need to be further studied.Model simulation is an important research method for land surface processes.Noah-MP is a new generation of land surface process model that is widely used,but the current research using it lacks lateral comparison and evaluation of heat flux simulation capabilities under different climates and land cover types,the simulation deviation is-180 to 180 W/m-2,the deviation is large.This study uses FLUXNET global observation data to drive and validate the model.Therefore,the performance of the observed heat flux under 5 climate zones and 9 land cover types was studied.The results show that except for arid climates,other climate types of heat flux have obvious seasonal changes.The quantity and distribution of sensible and latent heat flux are related to temperature and moisture,showing high heat flux in summer and low in winter,high sensible heat flux in dry types,features of high latent heat flux in humid types.From the point of view of the maximum heat flux,it decreases in order of tropical climate,arid climate,temperate climate,cold climate and polar climate.Observed heat flux throughout the year exists that the energy balance is not closed and there is an obvious time change.The energy balance residual error is large in summer and small in winter,high in daytime and low in nighttime.The energy balance rate?EBR?is closer to 1 in summer and daytime,and farther away from in winter and night.After research,the heat flux data of FLUXNET can be used for Noah-MP evaluationThrough a comprehensive model simulation,this study systematically assesses the uncertainty of Noah-MP sensible and latent heat flux simulation in 5 climate zones and9 land cover types.The result shows that the average error of sensible and latent heat flux simulation is-80?10 W·m-2 and-30?10 W·m-2at different types,respectively,The simulated deviation of the soil heat flux is small,between-4?4 W·m-2.With the largest simulation error found in the climate zone of tropical and arid,and land cover types of grassland,evergreen needle-leaved forest and deciduous broad-leaved forest.The sensible heat and latent heat during the day are underestimated,and the change of scheme combination can improve the simulation effect of heat flux.Rainfall will reduce the deviation level of heat flux.After studying the sources of uncertainty at heat flux simulation,it is found that vegetation land surface processes are the primary source of uncertainty in heat flux simulation,followed by water and soil land surface processes,the impact of water process on latent heat flux is greater than that on sensible heat flux.The Dynamic Vegetation Model?DVEG?is the dominant factor affecting vegetation process simulation,followed by Surface Exchange Coefficient for Heat,CH?SFC?,Canopy Stomatal Resistance?CRS?and Radiation Transfer?Rad?.The main influencing factors in the water land surface processes are runoff and groundwater?RUN?,snow/soil temperature integral?STC?,followed by rain and snow separation process?SNF?and super-cooled water process?FRZ?.Different climate classification data will not affect the conclusion of this study.For latent heat flux,the main components are canopy transpiration?FCTR?and surface evaporation?FGEV?,followed by canopy evaporation?FCEV?. |
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