FAO-PM法估算季节性冰冻地区路基土潜在蒸发蒸腾量

Application of FAO-PM Method to Estimate the Potential Evapotranspiration of Subgrade in Seasonal Frozen Regions

为准确估算东北东部山地润湿冻区(Ⅱ_(1)区)路基土平衡湿度,引入联合国粮农组织Penman-Monteith法(FAO-PM)估算气候因素控制型路基土潜在蒸发蒸腾量,以解决Thornthwaite法在负温时潜在蒸发蒸腾量计算值为0的问题。详细阐述了FAO-PM模型中5个气候因素的具体含义,并给出算例说明计算流程;根据Ⅱ_(1)区内6个气象台站月均气象数据计算得到各地路基土潜在蒸发蒸腾量;分析主要气候因素对路基土潜在蒸发蒸腾量的影响规律与程度。研究表明:Ⅱ_(1)区各地路基土全年潜在蒸发蒸腾总量为71.14~87.37 cm,负温时该值为8.27~12.39 cm,占全年总量的9.8%~15.7%;潜在蒸发蒸腾量与各地平均气温的显著正相关关系可在一定程度上削弱与其他气候因素的负相关关系;负温条件下,路基的潜在蒸发蒸腾量与平均气温、平均风速和平均日照时数呈正比,与平均相对湿度呈反比;FAO-PM法估算的逐月潜在蒸发蒸腾量与气象站实测数据的误差范围为0.47~13.22 cm,负温时误差范围为0.47~4.31 cm。因此,FAO-PM法适用于估算公路自然区划Ⅱ_(1)区路基土潜在蒸发蒸腾量,且具有可接受的估算误差。

In order to accurately estimate the equilibrium humidity of subgrade soil in the humid and frozen area of the eastern mountainous region of Northeast China(zone Ⅱ_1),the United Nations Food and Agriculture Organization-Penman Monteith method(FAO-PM) was introduced to estimate the potential evapotranspiration of climate-controlled roadbed soil,in order to solve the problem of the Thornthwaite method that calculated zero potential evapotranspiration at negative temperatures.The specific meanings of the five climate factors in the FAO-PM model were elaborated,and the calculation process was illustrated by examples.The potential evapotranspiration of subgrade soil in each region was calculated and obtained according to the monthly average meteorological data of 6 meteorological stations in zone Ⅱ_1,and the influence rule and degree of main climatic factors on the potential evapotranspiration of subgrade soil were analyzed.The results show that:the total potential evapotranspiration of subgrade soil in zone Ⅱ_1 throughout the year is 71.14~87.37 cm,which is 8.27~12.39 cm under negative temperature,accounting for 9.8%~15.7% of the total annual amount.The significant positive correlation between potential evapotranspiration and average temperature in various regions can weaken the negative correlation with other climate factors to some extent.Under negative temperature conditions,the potential evapotranspiration of the roadbed is directly proportional to the average temperature,average wind speed,and average sunshine hours,while inversely proportional to the average relative humidity.The error range between the monthly potential evapotranspiration estimated by the FAO-PM method and the measured data from meteorological stations is 0.47~13.22 cm,and the error range is 0.47~4.31 cm under negative temperature.Therefore,the FAO-PM method is suitable for estimating the potential evapotranspiration of subgrade soil in the natural zoning area Ⅱ_1 of highways and has acceptable estimation errors.