CCM3模式中LSM积雪方案的改进研究(Ⅰ):修改方案介绍及其单点试验

为了改进美国NCARCCM3全球模式中LSM陆面模型中的积雪方案的模拟效果,在Sun等1]SAST积雪模型的基础上,作了部分修改后,加进CCM3模式LSM模型中.该方案根据格点区域平均积雪深度的不同,把地面雪盖划分为1到3层不等,能在积雪表层和中间层更好地描述温度的日变化和季节变化;较详细地考虑了雪的热传导、太阳辐射的穿透吸收、雪的融化、液态水的储存、渗透和再冻结等积雪内部的主要物理过程;根据Nimbus-7卫星实测雪深资料修改了积雪覆盖度和雪面反照率的计算方案.利用前苏联6个台站1978-1983年的实测积雪资料和大气强迫数据,进行了单点模拟试验,结果表明,新的积雪参数化方案能够较好地再现积雪深度和雪水当量的逐日和季节变化特征,部分提高了积雪参数化方案对积雪的模拟能力.

Improvement Study on Snow Scheme in LSM Scheme of NCAR CCM3 Model(I):Introduction to the Modified Snow Scheme and Its Single Station Tests

To improve the simulation performance of the snow scheme of the LSM scheme of the NCAR CCM3 Model, a partly modified new snow scheme based on the SAST snow scheme has been incorporated into the LSM scheme of CCM3 Model and its single point tests have been run utilizing the observed snow data at six stations over the former Soviet Union and the atmospheric forcing in 1978_1983. The modified snow scheme has one to three snow cover layers according to the area mean snow depth of the grids and can better consider the diurnal and seasonal changes of temperature in the surface and mid layers of the snow cover; it takes account of the main physics processes, such as thermal conductivity, penetrated absorber of solar radiation, snow melting and frizzing and others; it modified the calculation scheme for both the snow cover rate and snow surface albedo. On other hand, the six single point snow simulated tests show that the new LSM snow scheme reproduces better the diurnal and seasonal changes in snow depth and snow water equivalent, and thus improve partly the snow simulation performance of the LSM scheme of CCM3 Model.