| The variation and simulation of water and heat fluxes is the forefront of academic topics of international concern.This research can provide a solid theoretical basis for water-saving agriculture.It is of great significance to understand the process of water and heat fluxes and optimize the construction of Farmland irrigation system.Based on the measured data of the eddy covariance system,a series of observations were made on typical farmland in the hilly area in south of Anhui province.This article conducted in-depth research in water consumption law and the law of energy distribution for the farmland.Applying the regression equation and the Penman-Monteith formula,We analyzed the changing process and control mechanism of farmland water consumption and energy allocation from different perspectives.On the basis of three canopy resistance models and one soil resistance model,the canopy resistance calculation model is improved and three new coupled resistance models are newly built.And we analysed and compared the three coupled resistance models,and then found the the best calculation method.At last,based on the canopy resistance model,the two methods of estimating evapotranspiration were compared.The results are here:（1）The daily change of corn’s ET in various growth stages have shown a regular bell-shaped curve.Seasonal changes in spring corn and summer corn are slightly different.Summer corn has higher ET value in the medium term,but spring corn’s ET is higher in the later period.The number of corn’s ET is mainly affected by net radiation and temperature;（2）In sunny daylight,when Rn-G is greater than 200W·m-2,the difference between EF is little and the energy is well distributed.The energy consumption is mainly for latent heat flux,followed by sensible heat flux.Canopy resistance plays an important role in energy distribution.（3）Coupling the canopy resistance model with the soil resistance model,three new coupled resistance models were created:critical canopy resistance model,climate resistance model and Jarvis multifactor factorial model.Then compared the measured values with the simulated values.The results show that the Jarvis multi-factorial factorial model is the most suitable for estimating the local corn evapotranspiration,followed by the critical canopy resistance model.If the measurement parameters are limited,we can use the canopy resistance model.Comparing the the simulated values of Penman-Monteith method with the simulated values of Shuttleworth-Wallace method,the result shows that the difference between the two method is not obvious when vegetation is more dense,but when the vegetation is sparse,the accuracy of SW estimation method is higher than PM estimation method.The simulated values of SW method is closer to the measured value. |
