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Study on Influences of Salinization on the Evaporation Processes in a Semi-arid Area in Western Australia

西澳大利亚半干旱地区盐渍化对蒸发过程的影响研究

基本信息

批准号：
15560447
负责人：
SHIMOJIMA Eiichi
金额：
$ 1.98万
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：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560447/
关键词：
evaporation salinization semi-arid area Western Australia observed data analysis evaporation experiment 半乾燥地

项目摘要

In order to clarify the relation between evaporation from the ground surface and salinization, a meteorological and hydrological observation was undertaken in a bare soil area in a semi-arid region (Yalanbee), Western Australia for three years from 2000. In this research, through analysis on that obtained data and a subsidiary evaporation experiment so on, that relation was investigated. The following was disclosed:(1) In the field, salty crust is formed by occurrence of evaporation in summer (dry season) and in. winter (wet season) soil is wetted by rainfall events. However albedo (reflection rate of solar radiation on the ground) in the dry season becomes by 10% smaller than that in the wet season. This reverse relation could not be recognized through an experiment using Yalanbee-soil and still remains as a future problem.(2) Albedo in the field in the dry season decreases with solar altitude, but its minimum was detected to appear not at noon but around 10 a.m. This is considered to … More be due to drying of ground surface by evaporation because reduction of soil wetness usually lets the albedo increase. This situation corresponds to such a result by a dome evaporation experiment that evaporation rate decreases abruptly from around 10 a.m. via its continuous increase from sunrise due to increasing solar radiation.(3) In the dry season, daily changes in atmospheric temperature-humidity and solar radiation cause the evaporation -condensation in the soil. Through a laboratory Yalanbee-soil column experiment under a meteorological condition similar to these actual variations, it was clarified that, when vapor movement in the soil layer is described by a diffusion equation, its modified diffusion coefficient becomes approximately 100 times larger than the original one. This increase is concluded to be caused by occurrences of evaporation and condensation, and structure and behavior of the modified coefficient were also clarified theoretically(4) In an evaporation experiment using the soil column with a shallow water-table, salty crust was observed to be formed non-uniformly on the upper soil surface and its development was very fast as the crust area became about 60% within about five days from the beginning of experiment. Also it was recognized that the evaporation rate decreased linearly with inverse of the crust area, and reduction in effective transferable cross-section for vapor leads to the decrease in vapor flux, evaporation rate, significantly. Less

为了弄清地表蒸发与盐碱化的关系，从2000年开始，在西澳大利亚州雅兰比的裸土区进行了为期三年的气象和水文观测。在本研究中，通过对所获得的数据进行分析，并结合辅助蒸发实验等，对这种关系进行了研究。(1)田间盐化结皮是夏季(旱季)和夏季(旱季)蒸发作用形成的。冬季(雨季)土壤因降雨事件而湿润。然而，旱季的反照率(太阳辐射在地面上的反射率)比雨季减小了10%。这种反向关系不能通过使用Yalanbee土壤的实验来识别，仍然是未来的问题。(2)旱季田间反照率随着太阳高度的增加而减少，但其最小值出现在上午10点左右，而不是中午。这被认为是…更多的原因是由于蒸发使地表干燥，因为土壤湿度的减少通常会使反照率增加。这种情况与穹顶蒸发实验的结果相对应，即蒸发速率在上午10点左右突然下降。在旱季，大气温湿度和太阳辐射的日变化导致土壤蒸发-凝结。通过实验室雅兰蜂土柱实验，在与实际变化相似的气象条件下，阐明了当水汽在土层中的运动用扩散方程描述时，其修正的扩散系数约为原来的100倍。并从理论上阐明了修正系数的结构和行为。(4)在浅埋深土柱蒸发试验中，观察到上层土壤表面形成了不均匀的盐化结皮，结皮面积在试验开始后的5天左右达到60%左右，盐化结皮的发展非常迅速。研究还发现，蒸发率与结壳面积成反比，蒸发率与结壳面积成反比，水蒸气有效可换截面的减小导致蒸发量和蒸发率显著降低。较少