不同冠层阻力模型对冬小麦返青-成熟期蒸散量估算的影响

蒸散量是农田水循环的重要组成部分，其准确估算对精准灌溉及农业节水具有重要意义。PenmanMonteith(P-M)模型是常用的估算方法之一，但冠层阻力/表面阻力的准确表达一直是应用中的难点。选取常用的7种冠层阻力模型，根据北京市顺义区2a(2020年和2021年)的波文比实测结果，对不同模型模拟的小麦冠层阻力及P-M估算的小麦蒸散量进行比较，并进一步分析影响小麦冠层阻力的主要因子。结果表明，7种模型均低估了小麦冠层阻力，同时高估了蒸散量。总体而言，Todorovic模型（TD）模拟效果最好，其模拟的冠层阻力和蒸散量的R2均大于0.605，平均偏差（MBE）分别为-82.8s·m-1和10.4W·m-2，相应的均方根误差（RMSE）分别为254.4s·m-1和33.5W·m-2；其余6种模型表现均较差，所模拟的冠层阻力R2仅0.113～0.241,MBE和RMSE在-236.4～-61.3s·m-1、277.2～373.8s·m-1；基于6种模型模拟阻力得到的小麦蒸散量与实测值的R2在0.046～0.184,MBE和RMSE分别在44.5～97.4W·m-2、81.4～147.9W·m...

Effect of Different Canopy Resistance Models on Estimation of Winter Wheat Evapotranspiration during Regreening-Maturing Stage

Evapotranspiration(ET) is an important component of farmland water cycle, and its accurate estimation is of great significance for precision irrigation and water-saving agriculture. The Penman-Monteith (P-M) model is one of the most commonly used estimation methods, but reliable representation of canopy resistance (r_s) has been a difficult problem in applying the P-M. In this paper, seven commonly used r_s models were selected to assess if their simulated r_s could be used with P-M to directly estimate winter wheat ET. The P-M simulated ET was compared with measured values by Bowen ratio energy balance (BREB) system in Shunyi, Beijing for two years (2020 and 2021), and the main factors affecting wheat rs were analyzed. The results showed that the seven models generally underestimated wheat canopy resistance and overestimated evapotranspiration. Overall, the Todorovic model (TD) performed the best, and the R² for simulated r_s and ET were >0.605, mean bias error (MBE) being −82.8s·m⁻¹ and 10.4W·m⁻², respectively, with root mean square error (RMSE) of 254.4s·m⁻¹and 33.5W·m⁻²; the other six models performed poor, and the R² for simulated r_s was between 0.113−0.241, MBE and RMSE, were between−236.4 to −61.3s·m⁻¹ and 277.2 to 373.8s·m⁻¹, respectively. The R² for simulated ET was between 0.046−0.184, MBE and RMSE were between 44.5−97.4W·m⁻² and 81.4−147.9W·m⁻², respectively. On basis of RMSE, the performing order was TD>FAO56-PM>Katerji-Perrier (KP)>Garcıá-Santos (GA)>idso (IS)>Jarvis (JA)>CO. The correlation between canopy resistance and various factors suggested that net radiation (Rn) affected the most on wheat rs, while air temperature (Ta) and canopy temperature (Tc) affected the least with the following specific order: Rn>leaf area index (LAI)>relative humidity (RH)>vapor pressure deficit (VPD)>soil moisture (θ)> canopy-air temperature difference (∆T)>Tc>Ta. This results better explained the good performance of TD model, and it considers the key factors affecting canopy resistance such as Rn, VPD and ∆T. In addition, it has no parameters to be calibrated, which makes it easy to use. The results of this paper provided a scientific basis for applying one-step approach to calculate the water consumption of winter wheat.