不同环境条件下土壤温度日变化的计算模拟

应用多孔介质中传热传质的数学模型，对夏天和冬天，环境风速分别为4m／s和1m／s以及环境相对湿度分别为35％和85％这3种情况下高为500mm，半径为250mm的圆柱土壤床中温度的日变化进行了比较。根据数值模拟的结果绘出土壤中不同深度处温度的日变化曲线表明：(1)土壤中各点的温度随气温和土壤表面获得的辐射能的周期性变化而呈周期性变化；(2)随着深度的增加，土壤温度受气温和太阳辐射的影内变小，温度变化的滞后效应越来越明显；(3)在夏天，一天的大部分时间土壤表层的温度高于深层的温度，冬天则恰恰相反；(4)风速对土壤表层的温度影内较大。风速越大，土壤温度降低得越多；(5)干燥气候下，由于土壤水分的蒸发制冷作用，一天中土壤各点的温度低于湿润气候下相应各点的温度，土壤表层尤为明显。

SIMULATION ON THE DAILY CHANGE OF SOIL TEMPERATURE UNDER VARIOUS ENVIRONMENT CONDITIONS

Using the mathematical model to describe heat and mass transfer in porous media,simulative comparisons on the daily change of soil temperature under different conditions for summer and winter,ambient wind velocity of 1m/s and 4m/s and ambient relative humidity of 35% and 85% have been conducted respectively,.The numerical simulations show that: (1) Soil temperature at each point changes periodically with the periodical changes of ambient temperature and solar radiation. (2) The impact on soil temperature posed by ambient temperature and solar radiation decreases with the increasing of the depth from the soil surface,the daily change period of temperature turns long increasingly,which implies the effect of temperature hysteresises is distinct. (3) During the most part of a day in summer,soil temperatures in the upper layer are higher than those in the deeper layer,whereas it is reversed in winter. (4) When wind speed is high,heat and mass transfer between the soil and the surroundings are enhanced,the higher the wind speed,the more the water evaporation,thereby the more heat is taken away from soil,which leads to a greater decrease of soil temperature,especially in the surface layer. (5) Due to the effect of water evaporation in dry climate,soil temperature at each point is lower than that of in humid climate.