降水时间降尺度方法对蒸散发模拟的影响

Effects of precipitation downscaling method on evapotranspiration simulation of land surface model

为了解雨强历时过程对地表蒸散发的影响作用,分别采用IBIS模型自带的天气发生器和一种基于雨强历时关系的降尺度模型,对长白山地区的日降水进行了降尺度模拟计算,并以计算的小时降水为驱动,利用IBIS模型对地区蒸散发进行模拟。对比分析的结果表明,IBIS模型自带的天气发生器模拟的降水强度明显偏低,导致地表蒸散发模拟结果偏大,而雨强历时模型可以较好地模拟降水和蒸散发过程。这说明降水模拟精度的提高有利于促进地表蒸散发的模拟效果,进而提高水循环过程的模拟精度。此外,针对两场不同雨量的降水,对比分析不同雨强和历时方案下蒸散发的变化,指出在日降水量相同的情况下,在雨强大、历时短的降水过程中,地表蒸散发总量较小,截留蒸发所占的比重较小,而土壤蒸发和植被蒸腾所占比重较大。

In order to recognize the effects of precipitation intensity and duration on the evapotranspiration,temporal downscaling simulation of daily precipitation in Changbaishan area is conducted using the weather generator of IBIS(Integrated Biosphere Simulator)model and a precipitation downscaling model based on precipitation intensity and duration.The calculated hourly precipitation is used as the meteorological drive and evapotranspiration is simulated using the IBIS model.The results show that the precipitation intensity simulated by the weather generator of IBIS model is obviously lower,leading to a higher evapotranspiration,while the results from the precipitation downscaling model match the observation data well.The accuracy of evapotranspiration simulation can be improved with the accurate precipitation downscaling.In addition,through the comparison of evapotranspiration variation under different schemes of precipitation intensity and duration based on two precipitation events in 2004,stronger precipitation intensity and shorter precipitation duration can decrease the total evapotranspiration and the proportion of canopy interception evaporation,and increase the proportion of soil evaporation and plant transpiration under the same daily precipitation.