涡动相关涡动相关仪观测蒸散量的插补方法比较

涡动相关仪在长时间连续观测中，观测数据会有不同程度的缺失。应用6种不同的插补方法（平均昼夜变化法MDV，非线性回归方法NLR，动态线性回归方法DLR，查表法LUT，FAO PM方法，HANTS方法）对北京密云站2007年涡动相关仪观测蒸散量数据进行了插补。结果表明： LUT方法在不同数据缺失时均得到较好结果（均方差小于8 W/m²）；MDV和NLR方法更适合于短时间数据缺失的插补； DLR和FAO PM方法在观测数据出现连续波动时插补结果较差。由LUT、DLR、NLR、HANTS、FAO PM方法得到的年蒸散量分别为395.8 mm、409.9 mm、393.5 mm、390.7 mm、399.4 mm，差异在2.3~19.2 mm之间变化。对比分析了LUT方法得到的年蒸散量（潜热通量）与净辐射、降水量以及LAS观测潜热通量间的变化规律，表明插补结果合理。

Comparison of the Gap Filling Methods of Evapotranspiration Measured by Eddy Covariance System

Data missing is inevitable in long term eddy covariance system measurement. Several gap filling methods are chosen and applied in the data sets of Miyun station in 2007. These methods include mean diurnal variation (MDV), look up tables (LUT), nonlinear regressions (NLR), Dynamic linear regression (DLR), Harmonic analysis of time series (HANTS) as well as the method of Penman Monteith recommend by Food and Agricultural Organization (FAO PM). The impacts of different gap filling methods on the evapotranspiration are investigated and the results are tested. The result shows: LUT method is stable in every data missing cases (RMSD less than 8 W/m²); MDV and NLR methods are more suitable for short data missing; The gap filling results of DLR and FAO PM methods are not good if the observed data have large change continuously. The Annual ET obtained by LUT, DLR, NLR, HANTS, FAO PM methods are 395.8mm, 409.9mm, 393.5mm,390.7mm,399.4mm. The difference between annual ET filled by different methods resulted in a range of 2.3~19.2mm per year. The annual ET obtained by LUT method is compared to net radiation, precipitation and latent heat flux measured by LAS; it is shows that the results are reasonable.