利用简单生物圈模式SiB2模拟青藏高原地表能量收支

Modeling of Surface Energy Budget in the Tibetan Plateau Using Simple Biosphere Model SiB2

利用简单生物圈模式SiB2模拟了西藏短草大草原安多观测站1998年7月15日至9月10日期间的地表能量分配、地表有效辐射温度和土壤湿度。季风期,平均冠层高度和叶面积指数大约分别为0.05m和0.5。实验地点基本代表了夏季藏北高原大面积特征。所用资料为全球能量与水循环实验GEWEX(Global Energyand Water Cycle Experiment)亚洲季风实验GAME(Asian Monsoon Experiment)的西藏观测期间安多观测站微气象实地测量。采用这些资料确定SiB2所需要的参数和初始值后,由该资料中半小时一次的太阳短波辐射、大气长波辐射、水汽压、气温、水平风速和降水驱动SiB2,最后将模拟结果与实际测量的湍流通量、地表温度和土壤湿度进行了对比,进一步检验SiB2对季风期间青藏高原稀疏草原地表能量分配的模拟能力。对比结果表明:(1)当模式低估净辐射0.2%时,模式分别高估感热、潜热和土壤热通量4%、13%和8%;(2)模式得出的地表温度偏高5%;(3)土壤湿度估计合理。总的来说,SiB2对辐射分量模拟结果的偏差相对较小,相关程度普遍比感热通量、潜热通量和土壤热通量的模拟结果高。

By using Simple Biosphere Model 2 （SiB2）, surface energy balance budget, surface effective radiative temperature, and soil moisture were modeled for the GAME/Tibet Amdo site in a Tibetan short grass prairie （Amdo station） from 15 July through 10 September 1998. During the monsoon period the mean canopy height and the leaf area index were 0. 05 m and 0. 5, respectively. The study site represented the prevailing conditions of the northern Tibetan Plateau. The model was initialized and driven by using in situ measurements. The forcing data consist of the short-wave solar radiation, atmospheric long-wave radiation, vapor pressure, air temperature, horizontal wind speed, and precipitation. The model outputs of radiation components, turbulent heat fluxes, surface effective radia-tive temperature, and soil moisture were compared against direct measurements. Results show that： （1） SiB2 overestimated sensible, latent, and soil heat fluxes by 4%, 13%, and 8% respectively when it underestimated net radiation by 0. 2%; （2） surface effective radiative temperature was underestimated by 5%; and （3） soil moisture was estimated reasonably. In general, radiation components simulated by SiB2 were more closer to measurements than heat fluxes with high degree of correlation.