改进Hargreaves模型估算川中丘陵区参考作物蒸散量

摘要

为提高 Hargreaves-Samani（HS）模型参考作物蒸散量（ET0）计算精度，该文基于贝叶斯原理利用川中丘陵区1954－2002年逐日资料对其温度指数、温度系数和温度常数进行改进，并使用2003－2013年资料以Penman-Monteith（PM）模型为标准评价HS改进模型计算精度与适应性。结果表明：HS改进模型参数在川中丘陵区各区均小于联合国粮农组织推荐值，并呈现出随纬度上升而增大的趋势；与PM模型计算结果相比，HS改进模型计算的ET0相对误差在川中丘陵区北部从14.2%～60.9%降至−1.1%～33.4%、中部从40.6%～92.6%降至16.9%～61.1%、南部从31.3%～96.0%降至8.5%～64.4%、整个川中丘陵区从32.1%～82.7%降至9.5%～52.6%；相关性分析表明， HS改进模型和PM模型计算的ET0回归曲线的斜率更接近于1（北部1.16、中部1.02、南部0.99、全区1.13），决定系数均达到0.85（P＜0.01）以上；趋势分析表明，HS改进模型和PM模型计算的ET0变化一致，年内均呈开口向下的抛物线状，年际均呈微小上升趋势。因此，基于贝叶斯原理改进的 HS 模型在川中丘陵区不同区域变异性较小，适应性较强，具有较高的计算精度，可作为川中丘陵区参考作物蒸散量简化计算的推荐模型。%Reference crop evapotranspiration (ET0) is an important part of water cycle and water balance. Accurate estimation of ET0 becomes vital in planning and optimizing irrigation schedules and irrigation systems management. Numerous methods have been proposed for estimating ET0, among which Penman–Monteith (P-M) model recommended by Food and Agriculture Organization of the United Nations (FAO) in 1998 since it provids the highest accurate results across the world wherever in an arid or humid environment. But the main problems computing ET0 by P-M model are its complicated nonlinear process and requirements of many climatic variables. Thus, there is an urgent need to develop a much simpler and more appropriate model in areas with limited data, such as the Hargreaves-Samani (HS) method, which is modified in this paper. In order to obtain more accurate HS model of ET0in hilly area of central Sichuan Basin, 3 parameters(including temperature index, temperature coefficient and temperature constant) were calibrated based on Bayesian Theory using daily meteorological data from 1953 to 2002. Then, the daily and monthly ET0 from 2003 to 2013 were computed by the modified HS model, original HS model and PM model. Compared with the value recommended by FAO (the temperature index, temperature coefficient and temperature constant are 0.0023, 0.5 and 17.8, respectively), the 3 parameters obtained from the modified HS model were much smaller, and increased by latitude (0.00213、0.46 and 16.5 in north zone, 0.00217, 0.44 and 16.36 in central zone, 0.00212, 0.44 and 16.21 in south zone). The ET0 calculated by PM model was taken as the standard, the relative error of modified HS model decreased form 14.2%-60.9% to -1.1%-33.4% in north, 40.6%-92.6% to 16.9%-61.1% in central, 31.3%-96.0% to 8.5%-64.4% in south, and 32.1%-82.7% to 9.5%-52.6% in whole hilly area of central Sichuan Basin. Through the correlation analysis, the slope of regression curve between ET0 calculated by PM model and ET0calculated by modified HS model were 1.16 in north(R2 = 0.91), 1.02 in central (R2 = 0.88), 0.99 in south(R2 = 0.88), and 1.13 in whole hilly area of central Sichuan Basin(R2 = 0.91), respectively.The trend analysis based on monthly ET0showed that the trend of ET0 based on modified HS model was the same as that from PM model, which performed as the downwards Quadratic parabola in one year but increasing slightly in years from 2003 to 2013. The relative error of ET0 obtained from the modified and original HSmodel was above zero, and the former was smaller. Therefore, the modified Hargreaves-Samani model based on Bayesian Theory is more adaptive and accurate, and can be used as a simple method for the calculation of ET0in hilly area of central Sichuan Basin.