湖北省潜在蒸散估算模型对比

Comparison of Models for Estimating Potential Evapotranspiration in Hubei Province

利用湖北省74个气象站1961~2011年逐日气象资料,通过与FAO56-Penman-Monteith（FAO-PM）模型潜在蒸散估算结果对比,从月、季、年际变化及不同干湿状况条件比较了PriestleyTaylor、Hargreaves及Thornthwaite 3种简化的经验模型在湖北省的适用性。结果表明：3种简化模型与FAO-PM模型计算的逐月潜在蒸散均存在一定偏差,Thornthwaite模型偏差最大且冬夏季偏差反位相,Priestley-Taylor模型偏差最小,Hargreaves模型各月间的偏差最为稳定。3种简化模型与FAOPM模型估算结果具有良好的线性关系,且在各区域间相对稳定,但不同季节和干湿状况下各有差异,其中Hargreaves模型各季节间和不同干湿状况下与FAO-PM模型的关系均最为稳定。在年际变化上,Priestley-Taylor和Hargreaves模型与FAO-PM模型计算结果年际波动基本一致,Thornthwaite模型与FAO-PM模型计算结果尽管在量值上较为接近,但年际波动偏小;Priestley-Taylor和FAOPM模型年潜在蒸散趋势变化基本一致,Hargreaves模型年潜在蒸散趋势变化微弱,而Thornthwaite模型年潜在蒸散趋势变化与FAO-PM模型相反。建议在湖北省气象资料匮乏或不便应用的情况下,作物模拟模型及气候变化等研究中采用Priestley-Taylor估算模型,日常干旱监测及水资源规划中采用Hargreaves模型,干湿气候区划等工作中可采用Thornthwaite模型。同时,使用中应基于FAO-PM模型对经验模型进行适当订正,模型订正应建立在季节或月尺度。

Based on the daily meteorological data from 1961 to 2011 of 74 stations in Hubei Province,FAO56-Penman-Monteith（ FAO-PM） equation and three other empirical equations according to Priestley-Taylor,Hargreaves and Thornthwaite were used to estimate the monthly potential evapotranspiration（ PET）,and the applicability of the three empirical equations were evaluated by comparing with the FAO-PM model from monthly,seasonally and yearly scales as well as under different conditions of dry,moderate and wet. Results showed that monthly PETs estimated by the three empirical equations showed great differences compared to that of FAO-PM,especially for the summer months. The PET estimated by the Thornthwaite equation had the largest error and opposite deviations in summer and winter months,the PET estimated by the Priestley-Taylor equation had the smallest error,and the PET estimated by the Hargreaves equation had the most stable deviations among different months. All in all,well relationships were found between PETs estimated by the three empirical equations and FAO-PM equation,and the three empirical equations were fairly stable in relationship with FAO-PM among different regions,thereinto,only the Hargreaves equation was consistent with FAO-PM in different seasons as well as under different dry /wet conditions. As to the yearly variation of PET,the Priestley-Taylor equation showed the best agreement with FAO-PM equation,while the Hargreaves equation only captured the yearly variability,the Thornthwaite equation gave a rather precise estimate in magnitude but an opposite trend and too small variability. It was recommended that in climate,crop and hydrologic modeling as well as climate change analysis the Priestley-Taylor equation should be employed,in the practical drought monitoring and irrigation schedule the Hargreaves equation would be the best,in dry /wet climate zoning the Thornthwaite equation might work well. Additionally,necessary corrections should be done based on the FAO-PM estimates if possible,and such a practice should be carried out on a monthly or seasonal timescale.