岷江源区Hargreaves法适用性与未来参考作物蒸散量预测

Adaptation of Hargreaves Methods and Prediction of Reference Crop Evapotranspiration in Minjiang River Headwater Region

利用岷江源区1961—2010年逐日气象数据,采用FAO 56 Penman-Monteith和Hargreaves公式计算参考作物蒸散量,并以FAO 56 Penman-Monteith为标准对Hargreaves公式适用性进行评价,通过对Hargreaves公式转换系数C0进行修正,建立基于月尺度的参考作物蒸散发公式,结合Reg CM4.0区域模型生成的温度数据,对未来(2011—2099年)研究区参考作物蒸散发量变化进行预测。研究结果表明:通过通径分析发现,在岷江源区气温是影响参考作物蒸散量最重要的气象因子,采用基于温度法的参考作物蒸散发公式具有理论依据;采用未修正的Hargreaves公式明显高估了该区域参考作物蒸散量,特别是在雨季4—10月;修正后的Hargreaves公式绝对偏差与相对偏差显著减小,与FAO 56 Penman-Monteith月值之间均方根误差RMSE为3.76 mm、效率指数EF为0.39、可决系数CD为0.84,吻合系数d为0.8,能够满足研究区参考作物蒸散发估算精度;在未来气候变化情景下岷江源区参考作物蒸散量总体呈增加趋势,气候倾向率为5.6 mm/(10 a)。

Evapotranspiration as a key link in the water migration of soil plant atmosphere continuum, it is of great significance for hydrological cycle process responses to global climate change. Accurate estimation of reference crop evapotranspiration （ ET0） is necessary in water resource management and utilization in further. In numerous methods proposed for estimating ET0, among which Hargreaves equation only requires temperature data, but there is a large deviation between Hargreaves and Penman- Monteith equation in different regions, recommend by the Food and Agriculture Organization （FAO） of the United Nations as the standard equation for estimating ET0. It is an urgent need to revise Hargreaves coefficient so as to build the appropriate equation applying less climatic factor in the area. Meanwhile, it is possible to estimate potential evaporation in future climate change by using the revised Hargreaves equation which only needs future temperature data from 1RegCM4.0, which is the most reliable predictive data in further. The temperature based Hargreaves equation is confirmed to have a theoretical basis because temperature is the most important meteorological factor affecting ETo through path analysis in the Minjiang river headwater region. The non-calibrated Hargreaves equation overestimated reference crop evapotranspiration, especially from April to October, and the maximum absolute deviation and relative deviation were 31.60 mm and 29. 7% , respectively. So it was necessary to adjust Hargreaves coefficient （AHC）. AHC at the monthly scale, obtained by regression-based local calibration, minimized absolute deviation and relative deviation between the calibrated Hargreaves and the FAO Penman- Monteith equation, and the root mean square error （RMSE） , modeling efficiency （EF） , index of agreement （d） and coefficient of determination （CD） , which were 3.76 ram, 0.39, 0. 8 and 0.84, were significantly lower than those of non-calibrated Hargreaves （ 14.66 ram, 5.74, 0.51 and 7.81 ）. The Hargreaves coefficient can meet the estimation requirements of ET0 in the study area, and it is available to predict ET0 in future. Under a future climate scenario, ET0 in the study area showed a increasing tendency, with a tendency rate of 5.6 mm/（ 10 a） , the increase, however, would be slowed down.