黄土高原砂壤土冻融过程的观测和模拟

Freezing/Thawing Process of Sandy Soil on the Loess Plateau: Observation and simulation

针对黄土高原冬季陆面过程,使用兰州皋兰地区冬季观测资料和水热耦合模式(SHAW),进行了观测资料和数值模拟分析.结果表明:冬季,黄土高原地区入射的太阳辐射较小,降水稀少,空气干燥,12月、1月及2月的月平均气温均低于0℃,净辐射很小,积/融雪期间,净辐射出现了负值.地表能量分配中感热潜热都很小,但感热相对潜热占主要地位,在无降水时期日平均潜热通量几乎都在10 W.m-2以下.水热耦合模式对地表能量中短波净辐射和长波净辐射模拟较好,感热通量和潜热通量的模拟存在一定的偏差.模式对浅层30 cm和40 cm土壤温度及土壤湿度模拟较为成功,模拟值对观测值的相关性较高,相关系数均达到0.87以上.土壤温度模拟偏高,土壤湿度的模拟稍偏低.

An off-line numerical simulation, which focuses on the winter land process, has been conducted on the Loess Plateau, using the Simultaneous Heat and Water Model（SHAW）and forcing by the observation data. Also the fundamental meteorological characteristics are analyzed. The following main results are revealed： The solar radiation and precipitation are small in the plateau in winter. The average air temperature is below zero in December, January and February. The net radiation is negative during snow deposition and melting period. The sensitive heat flux plays a predominant role relative to latent heat flux. The latent heat flux is small in the days without precipitation, no more than 10 W·m^-2. The simulation ability of the SHAW model is examined. It is verified that it can simulate the surface energy fluxes reasonably. The modeling results of net short-wave radiation and net long-wave radiation are well in winter, except for snow deposition and melting period. The soil albedo parameterization scheme is well. The simulated and observed soil temperature and soil moisture in shallow layer have a good agreement. There is a significant correlation between simulation and observation. The simulated soil temperature is on the high side and soil moisture is on the low side. The capability of simulating the soil seasonal freezing/thawing process in the Loess Plateau with the SHAW is testified.