阿克苏地区陆面蒸发的数值研究

NUMERICAL STUDY ON EVAPORATION OF LAND SURFACE IN AKSUO REGION

本文的试验地区——塔里木盆地阿克苏地区气候干旱,雨量稀少。本文详细地介绍了在土壤湿润不足情况下蒸发的计算方法,但由于人工灌溉的原因使试验地区的地下水位上升到1.5m至2m,故对小麦地的蒸散研究,找们不能完全采用干旱情况下的蒸发公式来处理,本文采用大气湍流边界层阻力的空气动力学方法来计算,并通过与波文比方法的比较,给出了小麦地总蒸散的时变化状况。同时利用土壤分层模式,给出了土壤表层与深层的体积含水量的模拟结果,并与实测值进行了比较,发现二者是基本一致的。

The study carries out a numerical simulation of land evaporation in arsuo region. Because the region is extremely dry with limited rainfall, the paper introduces in detail the computationmethod for evaporation under the condition of shortage of water. Because of artificid irrigation by Xujiang Geographical Institute, the underground water level is raised to 1. 5-2. 0m. In order to study the evaporation in wheat fields, we do not adopt completely computational formulae of evaporation under the condition of drought. Because climate changes are very abnormal, the author adopts aerodynamics method with the resistances in turbulent ABL to carry out numerical simulation. The vegetation in the model is wheat, and the soil is sandy loam. The date is 15 - 23, June, 1992. The soil suface is covered with wheat completely, therefore the model do not consider the condition of bared soils. The author gives the hourly change trend of the field evapo-transpiration by the comparison with measured data. The author studies the heat transport of the soil, emphasizes particularly on the temperature change between soil and the vegetation layer, and deals with the radiation balance. The paper structures the equation for temperature changes as: where Tc, Tgb, Tge, T are temperatures of vegetation layer, bared soil surface, soil surface under the vegetation and soils at 60cm deep layer respectively. This paper studies mainly the evapotranspiration intensity and the law of moisture changes of the field. Because of the close interrelation between evapotranspiration intensity and moisture change, the root with unsaturated moisture movement is divided into two layers (d1 thickness and d2 thickness), and the moisture movement processes in the two layers of soils are discussed in detail. The moisture change equations in the two layers of soils are: By coupling of the equations (4-1) and (4-2) , the whole water-heat change process can be simulated. This paper carries out the numerical simulation for the water-heat change processes in the soil-vegetation-atmosphere system of the Akesu region in the Tarim basin. The first section of the paper introduces in detail probable evaporation, the second section deals with evapotranspiration when short of moisture, and the third section gives the numerical simulation for actual evapotranspiration in the field. Finally, The numerical results are compared with the measured data. The numerical results are found to be essentially consistent with measured data.