利用区域气候模式RIEMS产品分析日蒸散量及其影响

Daily Evapotranspiration Calculated with RIEMS Model Output and Its Effect

利用区域气候模式RIEMS输出的各种气象参数,采用了BEF等4种不同方法计算了沂沭河上游流域的潜在蒸散量,并与该流域6个气象站实测蒸发数据计算的陆面潜在蒸散量进行了比较。结果表明,根据平均偏差、平均绝对偏差、均方根差和相关系数指标的综合判断,该4种方法的估测精度从高到低依次为双线性曲面回归经验函数法(BEF)、Hargreaves-Samani(Harg)法、Pristley-Tayler(P-T)法和Penman-Monteith(P-M)法。在时间序列上,4种方法计算的逐日蒸散量与观测值呈相同的变化趋势,但计算值在蒸散发最强、最弱和降水最多、气温最高的7-9月有较大差异。BEF法估测的精度最高,与观测值最接近,Harg法、P-M法和P-T法都有明显的偏高现象。BEF法只需要较少的参数就能得到较高的估测精度,因此可作为利用区域气候模式RIEMS产品计算沂沭河流域蒸散量的首选方法,进而为RIEMS模式中耦合的陆面水文过程模型TOPX提供满足精度要求的日蒸散量驱动参数。

The output products of the RIEMS model are used to calculate daily evapotranspiration （ET） using four different ET estimation methods, such as the modified Penman-Monteith method （P- M）, Priestley-Taylor method （P-T）, Hargreaves-Samani method （Harg） and the bilinear surface regres- sion empirical function method （BEF）. ET estimated from four methods were examined and compared with those so called ground truth transferred from the observed 20 cm evaporation pan data with validated evaporation pan coefficient from six weather stations in upper Yishuhe watershed of the study area. The results show that for the estimation accuracy of ET, BEF algorithns is in the first place; Harg, the see- ord; P-T, the third; and P-M, the fourth, based on four evaluation criterions such as mean bias, mean absolute bias, root mean square error and correlation coefficient. In the daily time series, ET estimation - from four approaches varies with the same trend to the observed evaporation pan generally, but has consid- erable difference in the strongest and the weakest evaporation duration, and in the maximum air tempera- ture and precipitation in July, August and September. As a whole, the ET estimated by BEF method per- forms best and has a good agreement with theobserved value, the other three approaches followed by Harg, P-T and P-M methods have an obvious overestimation. Because of the excellent performance of BEF method and less meteorological parameters needed for ET estimation with RIEMS predicted meteorological variables, BEF method was recommended as the best ET estimation approach to provide accurate ET for driving Hydrological process model TOPX coupled with RIEMS for the hydrometerological predictions in upper Yishuhe watershed, Shandong Province,.