Study Of Field Evapotranspiration Model And The Characteristics Of Underlying Surface Parameter Of The North China Plain (NCP)

The North China PIain(NCP)is one of the most important agricultural regions in China. But the scarcity of water resources in this area had hold back the agricultural production significantly. In order to resolve this question thoroughly, it is necessary to developing High-efficiency and Water-saving Agriculture and implementing accurate determination of irrigation water supply and irrigation time. The consumption of agricultural water resources in this area is primarily the field evapotranspiration. Therefore, the more accurate measurement and assessment of Field Evapotraspiration is especially for monitory crop and soil water condition.The field studies were conducted at Luancheng Agro-Ecological Experimental Station Located in the farmland of Taihang Piedmont from October 2002 to June 2004. With the advanced eddy correlation technique, a series of factors effecting Field Evaportranspiration, such as latent heat, sensible heat, net radiation and soil heat fluxes were measured. Further, together with the data of canopy temperature, the variance pattern of the canopy temperature and the canopy-air temperature differences, which are the important surface characteristic parameter effecting Field Evaportranspiration ,were analyzed. In so far, a model of Field Evaportranspiration and canopy-air temperature differences was construted. The results are as follows:The water heat fluxes resulted by the eddy correlation technique showed good accuracy and stability; During the growing stages of winter wheat, the canopy-air temperature differences and the Field Evaportranspiration between 13:40-13:50 on fine days were significantly related, and were described as an exponent model. The variance of LAI at different growing stages of winter wheat resulted in the discrepancy of the surface temperature and dir temperature. The key factors affecting the canopy temperature are the net radiation fluxes and the latent heat fluxes. There were dignigicant correlation between the air temperature differences and the relative soil moisture of 0~50cm soil layer.