干旱内陆区玉米田水热通量多层模型研究

Multi-layer model of water vapor and heat fluxes over maize field in an arid inland region

准确模拟农田水热通量对于干旱内陆区高效利用有限水资源具有重要意义。本文基于物质和能量交换多层模型(ACASA),增加C4作物光合、气孔导度对水分胁迫响应、玉米形态变化和根系非均匀吸水模块,修改土壤蒸发阻力和土壤水分运动参数计算模块,构建玉米田水热通量多层模型ACASA-M。根据实测值对模型关键过程进行参数率定,应用涡度相关系统实测水热通量进行模型验证。结果表明,ACASA-M能较好地模拟玉米田水热通量和土壤蒸发动态,也能模拟冠层内水热通量的时空分布;最大光合能力和叶面积指数非线性交互影响潜热通量;CO2浓度升高会减小潜热通量和冠层导度,增大感热通量。总之,该多层模型既可用于水热通量的模拟和预报,也可作为评价变化环境对农田耗水影响的有力工具。

The accurate modeling of water vapor and energy exchanges in cropland is needed to improve our ability to use limited water resources efficiently. Based on the multi-layer model of mass and energy ex-changes, ACASA, a multi-layer model of water vapor and heat fluxes over maize field, ACASA-M,has been developed. The new four modules were added including photosynthesis of C4 crop, the stomatal re-sponse to water stress, morphological changes of maize, heterogeneous uptake of root. Other two modules were modified including resistance of soil evaporation （Es） and the characteristic parameters of soil water. The model was parameterized by actual measurements and validated by eddy covariance measurements. The results show that ACASA-M could better simulate water and heat fluxes and variations of Es. The model could also simulate spatial and temporal distributions of fluxes within canopy. Model sensitivity tests re-vealed that variations in leaf area index and photosynthetic capacity interacted curvedly to increase rates of latent heat flux （λET）. Simulations indicated that the enhanced CO2 concentration would decrease λET and canopy conductance, and increase sensible heat flux. In general, the model can be used to simulate and predict water vapor and heat fluxes, and a powerful tool for evaluating the effect of environmental changes on water consumption in cropland.