Relationships between evaporation-precipitation and salinization in a semi-arid area

半干旱区蒸发降水与盐渍化的关系

• 批准号: 13650574
• 负责人: SHIMOJIMA Eiichi
• 金额: $ 2.18万
• 依托单位: Daido Institute of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13650574/
• 关键词: semi-arid area; evaporation from ground surface; salinization; sand column; experiment; numerical simulation

A relation between evaporation and salinization in a semi-arid area was explored through a column evaporation experiment and a numerical simulation.A sand column 100 cm long and 10 cm in diameter made using a sandy soil in Western Australia was installed on a balance, where via a draining process, a shallow water table (Case A) or a uniformly distributed water content profile in field capacity (Case B) was set. By exposing Its upper surface to ambient air controlled at 25℃and 20 % of RH, the evaporation experiment was started, where, when a solar radiation was simulated, a heat flux at 550 W/m^2 was applied on that surface. The following was recognized. Chemistry of soil-water formed through a rapid dissolution of sand particles was mainly Cl, Na^+, Mg^<2+> and showed a high concentration. Dryness in a zone near the sand surface, in particular, for Case B was more advanced and salinization was also much more developed, where the evaporation zone moved down to 2 cm deep (for Case A, 1 cm). For every case a crust was formed on the sand surface and its thickness for Case B was 5 mm after 40 days. Upward transport resistance for vapor generated by evaporation was estimated one-order of magnitude larger in the crust than that in fairly dried zone overlying that front. Only in the case that heat was applied, a downward movement of vapor appeared.Based on a vertically one-dimensional numerical model on moisture, vapor heat and a chemical component, the hydro-meteorological data observed over a sand dune in semi-arid area in Western China (HEIFE) were reproduced well after improvement on bulk coefficients of turbulent transport from surface, albedo and emissivity of infrared radiation. A characteristic of solute concentration profile observed there could be reproduced by 10-year calculation.

通过柱蒸发实验和数值模拟探讨了半干旱地区蒸发与盐碱化的关系。将利用西澳大利亚沙土制成的长100 cm、直径10 cm的沙柱安装在天平上，通过排水过程设置浅地下水位（工况A）或均匀分布的田间持水量剖面（工况B）。通过将其上表面暴露在控制在25℃和20％RH的环境空气中，开始蒸发实验，在模拟太阳辐射时，在该表面上施加550 W/m^2的热通量。以下内容得到认可。沙粒快速溶解形成的土壤水化学成分主要为Cl、Na^+、Mg^2+，且浓度较高。特别是在案例 B 中，靠近沙面的区域干燥程度更高，盐化也更加发达，蒸发区向下移动到 2 厘米深（案例 A 为 1 厘米）。对于每个案例，沙子表面都会形成硬壳，案例 B 的厚度在 40 天后为 5 毫米。据估计，地壳中蒸发产生的蒸汽的向上输送阻力比该锋面上相当干燥的区域大一个数量级。只有在施加热量的情况下，水蒸气才会出现向下运动。基于水分、水蒸气热和化学成分的垂直一维数值模型，改进了地表湍流传输的体积系数、反照率和红外辐射发射率，很好地再现了中国西部半干旱地区沙丘上空观测的水文气象数据。在那里观察到的溶质浓度分布特征可以通过 10 年计算来重现。

项目成果

上田剛, 玉川一郎: "乾燥地における熱・水収支の数値計算的研究"日本気象学会2001年春季大会講演予稿集. 234 (2001)

Tsuyoshi Ueda、Ichiro Tamakawa：“干旱地区热量和水平衡的数值研究”日本气象学会 2001 年春季会议记录 234 (2001)。

下島栄一, 平尾和久, 堀内将人, 玉川一郎: "半乾燥地での蒸発-塩類集積の関係"水文・水資源学会研究発表会要旨集. 190-191 (2002)

Eiichi Shimojima、Kazuhisa Hirao、Masato Horiuchi、Ichiro Tamakawa：“半干旱地区蒸发与盐分积累的关系”日本水文水资源研究会摘要190-191（2002）。

Eiichi Shimojima, Kazuhisa Hirao, Masato Horiuchi and Ichiro Tamagawa: "Relation between Evaporation and Salinization in a Semi-Arid Area"Proc. Annual Conference, Japan Soc. Hydrol. and Water Resour.. 190-191 (2002)

Eiichi Shimojima、Kazuhisa Hirao、Masato Horiuchi 和 Ichiro Tamakawa：“半干旱地区蒸发与盐碱化的关系”Proc。