Study On Water And Heat Exchange Characteristics And Evapotranspiration Model In The Red Hilly Region Of Southern China

The characteristics of water and heat fluxes at different time scales in red soil area,their influencing factors,evapotranspiration changes and the applicability of evapotranspiration models are of great significance for fully grasping the water and heat resources and regional water consumption laws in the study area,as well as for effective irrigation and improved water use Rate to provide a scientific basis.In this paper,the farmland in the low-lying red soil area of Yujiang County,Yingtan City,Jiangxi Province is taken as the research object,and the data of large-aperture scintillometer,automatic weather station data and soil heat flux data are used as the research data to analyze the test area from 2017 to 2019.The variation characteristics and dominant factors of each component of the energy balance day by day and month by month are compared to analyze the regional applicability of the four models to provide a reference for the regulation of water and heat resources and drought prevention and drought resistance in the study area.The main findings are as follows:(1)The components of the energy balance generally change in a single-peak type under typical weather conditions.The law of change is high in the day and low in the night,and is obviously affected by weather conditions.The latent heat flux and the net radiation change at the tenth and monthly scales are more synchronous,and are closely related to the weather conditions.They generally decrease with the month,and the sensible heat flux is the opposite.The maximum value occurs in September and October.In general,the net radiation flux is the largest in 2019,and the latent heat flux is the largest in 2018.The main form of energy exchange in the study area in different years and at different time scales is latent heat exchange,followed by sensible heat exchange.(2)There are differences in meteorological conditions in different years,but the trend of change is more consistent.The average daily total net radiation flux in 2017-2019 is 9.96,10.82,11.41,and the average temperature is 26.7 ℃,26.2 ℃,28.0 ℃.The order of average wind speed in different years is 2017> 2018> 2019,and the order of how much water vapor content in different years is 2017> 2019> 2018.(3)Rn(net radiant flux)is the main decision factor of latent heat flux on a daily and hourly time scale,which directly affects the main part.At the daily scale,T(air temperature)has only the second largest influence on latent heat flux,and the indirect influence occupiesthe main part.The influence path is mainly interacted with Rn.RH(relative humidity)has an inhibitory effect on latent heat flux,mainly through indirect effects through interaction with Rn.At the time scale,the correlation coefficients of Rn,T,WS(2m wind speed)and latent heat flux all decreased in 2017,and the correlation coefficients of RH and latent heat flux increased significantly.After the downscaling,T is no longer a decision factor in 2018 and2019.The correlation coefficient of Rn and latent heat flux has increased in 2018,and the absolute values of the correlation coefficients of other factors have declined.The direct effect of Rn on latent heat flux in 2019 Has been enhanced.(4)The simulation results of the four models show that the FAO98 Penman-Monteith model has the best simulation effect and is closest to the reference value,with an overestimation of about 0.75%,followed by the Priestley-Taylor model,with an underestimation of 15% The evapotranspiration of Irmark-Allen model is obviously overestimated,which can only explain 89% of the evapotranspiration,and the simulation effect on the peak and valley values of evapotranspiration is poor,and the simulation effect of Makkink model is the worst,which is very different from the reference value,not very Good reflection of regional evapotranspiration.