积雪季节变化特征的数值模拟及其敏感性试验

NUMERICAL SIMULATION OF THE EVOLUTION OF SNOW COVERAND ITS SENSITIVITY EXPERIMENTS

文中利用综合陆面模式 (ComprehensiveLandSurfaceModel,CLSM )对法国ColdePorte 1 993/ 1 994 ,1 994 / 1 995年及BOREASSSA OJP 1 994 / 1 995年积雪个例进行了模拟试验 ,通过模拟结果与观测资料的对比 ,检验了CLSM对积雪变化特征的模拟能力 ,并通过敏感性试验探讨了降雪密度、积雪持水量等积雪参数化方案及植被对积雪模拟可能产生的影响。结果表明 :(1 )CLSM能够准确地模拟出积雪的变化过程 ,对积雪的演变特征作出了合理的描述 ;(2 )降雪密度、积雪持水量参数化方案对积雪模拟结果均具有一定的影响 :降雪密度参数化主要对积雪深度的模拟产生影响 ;而积雪持水量参数化方案对积雪的演变过程 ,尤其是积雪的消融 ,具有重要的作用 ;(3)有、无植被存在的情况下 ,积雪 土壤系统的变化过程存在显著的差别 ,植被通过改变积雪 /土壤表面的能量平衡 ,对积雪及土壤的变化过程产生重要影响 :植被的存在有利于积雪的维持 ,使得积雪融化进程推迟 。

By using Comprehensive Land Surface Model (CLSM), three snow cases, i.e., France Col de Porte 1993/1994, 1994/1995 and BOREAS SSA-OJP 1994/1995, are simulated. The simulated results were compared with the observations to examine the capability of the model to describe the evolutions of snow cover under two different land cover conditions. Several sensitivity experiments were performed to investigate the effects of some snow cover internal processes parameterizations and vegetation on the model results. Results suggest that CLSM simulates the basic processes of snow cover accurately and discribes the features of the snow cover evolutions reasonably, indicating that the model has the potential to model the processes related to snow cover evolution. It was also found that the different parameterization schemes of the snowfall density and snow water holding capacity have significant effects on the simulation of snow cover. The estimation of snowfall density mainly impacts the simulocted snow depth, and the underestimation (overestimation) of snowfall density increases (decreases) snow depth simulated significantly with little effect on the simulated snow water equivalent (SWE). The parameterization of snow water holding capacity played crucial roles on the evolutionp of the snow cover, especially on the ablation of snow cover. A larger snow water holding capacity usually led to large snow density and heat capacity by storing more liquid water in the snow layer, and made the temperature of the snow cover and snow ablation varies more slowly. To a smaller snow water holding capacity, contrary was the case. The results also shows that the physical processes related to the snow cover variation were different whether vegetation exits or not. Vegetation played an important role in the evolution of soil-snow system by changing the energy balance at the snow-soil surface. The existence of vegetation is favorable to the maintance of the snow cover and delays increase underlying soil temperature.