AN IMPROVED LAND-SURFACE PROCESSES MODEL AND ITS SIMULATION EXPERIMENT PART1: LAND-SURFACE PROCESSES MODEL (LPM-ZD) AND ITS “OFF-LINE” TESTS AND PERFORMANCE ANALYSES

Based on the existing (mainly BATS model) land-surface schemes and models,a new Land-surface Processes Model (LPM-ZD) has been developed.Ithas the following major characteristics: 1.The combination of physical equations with empirical analytical formulae are used to constructthe govereningequations of soil temperature and moisture.Higherresolution of model level and physical equations are adopted for upper soil layers,and for the low soil layers,lowerresolution of model level is adopted and empirical analytic formulae are used. 2.In the land surface hydrolog ical processes,the sub-grid distribution of precipitation and its effects are taken into account. 3.A simple snow cover model has been used in LPM-ZD which includes effects of snow coveron soil thermo dynamics and hydrology,as well as albode. By use of model LPM-ZD and three groups of point observation data,a series of "off-line" tests have been carried out.The simulation results indicate that LPM-ZD has good performance and can accurately simulate diurnaland seasonal variation of land surface pro cesses for many kinds of land-surface covers (forest,grass,crops and desert) in different climate zone.The results simulated by LPM-ZD are consistent with the observations.Later,by use ofone group of observation data and LPM-ZD,a series of sensitive experiments have been done.It is shown that LPM-ZD is much sensitive to some parameters,such as initial soil moisture,vegetation physical parameters as wellas subgrid distribution factor μ of precipitation.Therefore it is much important for land-surface processes model to define these parameters as accurately as possible.