根系吸水过程参数化方案对青藏高原陆面过程模拟的影响研究

根系吸水过程对地表能量平衡和水循环起着重要作用,目前不同的根系吸水过程参数化方案对青藏高原陆面过程模拟的影响尚不明确,探讨相关参数化方案的影响,可以为今后建立陆面过程模式根系参数化方案提供参考。本文利用2010年6月1日至9月30日青藏高原玛曲站的观测资料作为大气强迫资料,驱动BCC_AVIM模式（北京气候中心陆面模式）引入不同的根系吸水过程参数化方案,对玛曲站2010年6月1日至9月30日时段感热通量、潜热通量、土壤温度、土壤含水量等要素进行数值模拟,分析根系吸水过程参数化方案对青藏高原地区陆面过程的影响。模式中有关根系吸水过程的参数化方案主要分为根分布模型和土壤水分对根系有效性函数两类,根分布模型用Jackson方案、Schenk方案替换,土壤水分对根系有效性函数用Li方案、LSM1.0方案、CLM4.5方案替换。对比结果表明:不同的根系吸水过程参数化方案对土壤温度、土壤含水量的模拟影响较小,对感热通量、潜热通量模拟影响较大,尤其对冠层蒸腾量模拟差异显著,相关参数化方案的变动直接影响冠层蒸腾量。两类方案模拟的差异受降水的影响,在多雨期,根分布对比方案与原模式方案模拟的感热、潜热通量间存在较大差异;在少雨期,土壤水分对根系有效性函数对比方案与原模式方案模拟的感热、潜热通量间存在较大差异。

Effect of the Root-Water-Uptake Process Parameterization Schemes on the Land-Surface-Process Simulation in the Qinghai-Tibet Plateau

The root-water-uptake process plays an important role in maintaining the surface energy balance and water cycle. Currently, the influence of different root-water-uptake parameterization schemes on the simulation of the land surface processes in the Qinghai-Tibet Plateau is unclear. This study intends to explore the influence of these parameterization schemes and provide a reference for establishing root parameterization schemes for the future development of a land-surface-process model. Using the Beijing Climate Center Land Model (BCC_AVIM), we applied different root-water-uptake parameterization schemes and used the meteorological data observed at the Maqu station in the Qinghai-Tibet Plateau from June 1, 2010, to September 30, 2010, as the forcing data to simulate sensible heat flux, latent heat flux, soil temperature, and soil water content at the Maqu station. We subsequently compared the simulation results obtained using different parameterization schemes in case of the Qinghai-Tibet Plateau. We divided the root-water-uptake parameterization scheme into a root distribution model and a soil-water-availability function for roots. Further, we based our root distribution model on the Jackson and Schenk schemes and the soil-water-availability function for roots on the Li, LSM1.0 (Land Surface Model 1.0), and CLM4.5 schemes. A comparison of the results denotes that different parameterization schemes have little impact on the soil temperature and the soil water content but a considerable impact on the sensible and latent heat fluxes, especially with respect to canopy transpiration. We observed that the differences between the simulation results were related to precipitation. During the rainy period, the simulated root distribution model is considerably sensitive, with a large difference being observed between the sensible and latent heat fluxes simulated by the original model. During the less rainy period, the simulated soil-water-availability function for roots is more sensitive, with a large difference being observed between the sensible and latent heat fluxes simulated by the original model.