Study On Land Surface Process And Offline Experiments Of Land Surface Process Model

This paper includes three parts. The first one is to study the relationship between soil moisture and precipitation over the Shiguanhe River Catchment in the summer of 1998 and 1999. The second part is to evaluate the performance of a modified BATS land surface model by offline experiments. The third is sensitivity experiments by the modified BATS model on soil texture and soil color.Based on the daily and hourly precipitation observation and daily soil moisture observation in Meishan, Nianyushan and Jiangji station in Shiguanhe River Catchment over the Huaihe River basin in summer of 1998 and 1999, the temporal variations of the precipitation and soil moisture of this three stations and their relationship are analyzed in this study. The results indicate that soil moisture and precipitation have an obvious trend, and there is a positive lagged correlation between soil moisture and precipitation. The results also show that the spatial distributions of soil moisture and precipitation are heterogeneous.By use of a single station data in Siberia area and 1998 GAME/HUBEX IOP data the performance of a newly modified BATS land surface process model are evaluated. The results show time interval of atmospheric forcing gives rise to significant difference in net solar radiation and latent heat in Siberia area. The model can reproduce the variations of surface characters reasonably in semi-wetness areas in summer in China. The simulations of ground temperature and earth absorbed net solar radiation are lower than the observation. Sensible heat and latent heat are also lower than the observation. Further study will be carried out to improve the model simulations by choosing proper soil and vegetation parameters.Four series of sensitivity experiments have been carried out to examine the modified BATS sensitivity to soil color and soil moisture. The results show the model has greatest sensitivity to the soil texture variation, but has little response to soil color. Coarse soil is easy to lost moisture and get little water in soil. Clay haslarge soil moisture because of it's strong capacity. The coarse soil absorb small solar radiation due to high albedo. The simulated latent heat of coarse soil is smaller, and surface temperature and sensible heat is larger than the results of the control run. The fine soil characters have little variation of albedo and absorbed solar radiation. The simulated sensible heat is lower than the result of the control run in clay case.