数値シミュレーションによる裸地蒸発に関する研究(2)-蒸発に及ぼす風速変化の影響-

Abstract

Wind speed in turbulent boundary layer developed above ground surface usuallychanges with time in various scales. It is well known that the wind speed plays akey role in the evaporation from bare land. In practice, it is important to clarifythe effect of variation of wind speed with a relatively long periodicity on theevaporation, because we often need a mean evaporation rate as diurnally averaged.In order to investigate the effect of the time variation of wind speed in arelatively long time-scale on the evaporation from bare land, a numerical simulationhas been undertaken. In the simulation, assuming that a land condition is uniformand a meteorological condition is horizontally uniform, one-dimensional fundamentalequations of water and heat in the evaporation field as an atmosphere-landcontinuum were set. Water table was in particular set to be located at a decideddepth under the ground surface. Through the calculation it is stressed on that, when the wind speed changes periodically and randomly with time, the averageevaporation rate can be given by evaporation rate at the averaged wind speed.