In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mecha...In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.展开更多
为提高现有作物生长模型单产模拟精度,明确土壤水分供需变化与产量之间的动态关系,该研究构建了水文—作物生长耦合模型SWAT-EPIC(soil and water assessment tool-environmental policy integrated climate)。基于参数敏感性优化的扩...为提高现有作物生长模型单产模拟精度,明确土壤水分供需变化与产量之间的动态关系,该研究构建了水文—作物生长耦合模型SWAT-EPIC(soil and water assessment tool-environmental policy integrated climate)。基于参数敏感性优化的扩展傅里叶幅度敏感性检验算法(extended fourier amplitude sensitivity test,E-FAST),在陕北黄土高原建立包含土壤碳动态评估的苹果单产评估体系。结果表明,优化后的模型在旱作苹果单产的模拟精度误差减少了38.98%,模拟RMSE=2.56%,RRMSE≈9.8%,具有良好的模拟性能。降水对果园浅层土壤水分补给具有直接作用,而深层水分持续消耗加剧干旱胁迫,成为限制苹果单产提升的关键因素。此外,农地改种果园后0~10m土壤有机碳储量提升了14.85%。本研究表明,通过整合水文过程与作物生长机制,SWAT-EPIC耦合模型能够更全面反演区域水分与产量的响应关系,为干旱区果园水分管理与可持续高产提供科学依据。展开更多
土壤湿度是控制陆—气界面潜热和感热通量分配的关键要素之一,而且由于其具有一定的记忆特性,可以对多种时空尺度的天气气候过程产生重要影响。在数值模式中,土壤水力参数的不确定性是导致土壤湿度模拟结果不确定性的主要原因之一。本...土壤湿度是控制陆—气界面潜热和感热通量分配的关键要素之一,而且由于其具有一定的记忆特性,可以对多种时空尺度的天气气候过程产生重要影响。在数值模式中,土壤水力参数的不确定性是导致土壤湿度模拟结果不确定性的主要原因之一。本文基于银河全球大气谱模式YHGSM(Yin He Global Spectral Model)的陆面模块,引入了VG(van Genuchten)土壤水分特征曲线模型,并探讨了模型水力参数的两种不同取值方案对土壤湿度离线模拟以及全球中期数值天气预报的影响。其中,土壤水力参数所需要的土壤类型数据来源于全球土壤数据集GSDE(Global Soil Dataset for Earth System Models)。离线试验结果表明,除了冻土和有机土壤的模拟偏差较大外,YHGSM的陆面模块对全球大部分地区土壤湿度的模拟能力较好,模拟精度与ERA5土壤湿度再分析产品的精度近似;土壤水力参数的不同取值方案对土壤湿度模拟有一定影响,其影响程度与土壤类型和局地气候条件密切相关,粗质地和中等质地土壤对模型参数的敏感性更强。从全球中期数值预报结果来看,土壤水力参数通过改变土壤湿度模拟,不仅对近地层温、湿度的短期预报结果产生重要影响,而且可能会导致预报系统积分6天后的大尺度环流场发生显著变化。因此,对于全球中期数值预报系统而言,优化土壤水力参数,提高土壤湿度模拟能力是非常重要的。此外,对于数值预报系统而言,正确模拟土壤湿度随时间的变化特征可能要比土壤湿度模拟值大小的准确与否更加重要。展开更多
基金Projects(51878064, 51378072) supported by the National Natural Science Foundation of ChinaProjects(300102218408, 300102219108) supported by the Fundamental Research Funds for the Central Universities, China。
文摘In arid regions, water vapor diffusion predominates the total water migration in unsaturated soil, which significantly influences agriculture and engineering applications. With the aim of revealing the diffusion mechanism of water vapor in unsaturated soil, a water vapor migration test device was developed to conduct the water vapor migration indoor test. The test results demonstrate that the characteristics of water vapor diffusion in unsaturated soil conformed to Fick’s second law. A mathematical model for water vapor diffusion under isothermal conditions in unsaturated soil was established based on Fick’s law. Factors including the initial moisture content gradient, initial moisture content distribution, soil type and temperature that affect the water vapor diffusion coefficient were analyzed. The results show that there was good agreement between the moisture content calculated by the mathematical model and obtained by the indoor experiment. The vapor diffusion coefficient increased with increasing initial moisture content gradient and temperature. When the initial moisture content gradient is constant, the vapor diffusion coefficient increases with the increase of matrix suction ratio in dry and wet soil section. The effect of soil type on the water vapor diffusion coefficient was complex, as both the moisture content and soil particle sizes affected the water vapor diffusion.
文摘土壤湿度是控制陆—气界面潜热和感热通量分配的关键要素之一,而且由于其具有一定的记忆特性,可以对多种时空尺度的天气气候过程产生重要影响。在数值模式中,土壤水力参数的不确定性是导致土壤湿度模拟结果不确定性的主要原因之一。本文基于银河全球大气谱模式YHGSM(Yin He Global Spectral Model)的陆面模块,引入了VG(van Genuchten)土壤水分特征曲线模型,并探讨了模型水力参数的两种不同取值方案对土壤湿度离线模拟以及全球中期数值天气预报的影响。其中,土壤水力参数所需要的土壤类型数据来源于全球土壤数据集GSDE(Global Soil Dataset for Earth System Models)。离线试验结果表明,除了冻土和有机土壤的模拟偏差较大外,YHGSM的陆面模块对全球大部分地区土壤湿度的模拟能力较好,模拟精度与ERA5土壤湿度再分析产品的精度近似;土壤水力参数的不同取值方案对土壤湿度模拟有一定影响,其影响程度与土壤类型和局地气候条件密切相关,粗质地和中等质地土壤对模型参数的敏感性更强。从全球中期数值预报结果来看,土壤水力参数通过改变土壤湿度模拟,不仅对近地层温、湿度的短期预报结果产生重要影响,而且可能会导致预报系统积分6天后的大尺度环流场发生显著变化。因此,对于全球中期数值预报系统而言,优化土壤水力参数,提高土壤湿度模拟能力是非常重要的。此外,对于数值预报系统而言,正确模拟土壤湿度随时间的变化特征可能要比土壤湿度模拟值大小的准确与否更加重要。
