Research On Variation Law Of Sensible Heat Flux In Typical Farmland Based On Large Aperture Scintillometer

Based on the field data of typical croplands of winter wheat-summer maize in Daxing District of Beijing in September 2013 to September 2016,the sensible heat flux was analyzed by the large-aperture scintillator and the vorticity-related system.The main results are as follows:1.Based on the analysis of LAS footprint model,the representative of the flux space of bare land,winter wheat and summer maize in the whole growth period were analyzed.The contribution of the source region P?contribution rate?= 80% of winter wheat mature was the largest and the summer maize tassel period was the smallest.2.In the case of other parameters were not changed,The contribution of the source region P?contribution rate?= 80% of different erection height and erection distance of were different.Three erection height were simulated in the experiment which were 29.6m,19.6m,9.6m and the contribution of the source region P?contribution rate?= 80% of them were 127491m²,103352m²,83959m².Three erection distance were simulated in the experiment which were 620 m,1240m,2480 m and the contribution of the source region P?contribution rate?= 80% of them were 532451m²,130323m²,107551m².3.It is different in sensible heat flux between bare land,winter wheat and summer maize in the whole growth period.The mean value of sensible heat flux of bare land was the largest.The mean value of sensible heat flux of filling period of winter wheat was the largest,and the smallest was heading date of winter wheat.The mean value of sensible heat flux of mature period of summer maize was the largest.The smallest was filling period of summer maize.The maximum of sensible heat flux was occurred in 12¹4 o'clock around and the minimum at night.With the increase of soil moisture content,the sensible heat flux decreases.The higher the canopy height the greater the daily average of sensible heat flux.4.The correlation between the sensible heat flux and the solar radiation?Rn?in the bare land,winter wheat and summer maize were positively correlated,the average correlation coefficient was about 0.4811.The average correlation coefficient between sensible heat flux and T was only 0.1368,the correlation was not obvious.The average correlation coefficient between sensible heat flux and Ws was 0.9076,the correlation was particular obvious.5.The range of atmospheric refraction?C_n²?fluctuates of bare land,jointing period,tasseling period,filling period of summer maize was big,which was 4 × 10^-14 to 5.17 × 10^-14,and the atmosphere was in a relatively unstable state,turbulence effect was relatively strong,the heat flux was big.But the range of C_n² fluctuation of winter wheat in the whole growth period and mature period of summer maize was small,which was 2.60 × 10^-14 m^-2/3 to 4.02 × 10^-14 m^-2/3,and the atmosphere was in a stable state,turbulence effect was weak and the sensible heat flux was small.The range of bowenratio in bare land was big,the range was-79.29 to106.39,and the range of bowenratio in winter wheat and summer maize in the whole growth period was small,the ratio of sensible heat flux and latent heat flux varies was weak.The atmosphere was in a relatively unstable state in bare land jointing period,heading of winter wheat and mature of summer maize,turbulence effect was relatively strong,the heat flux was big.and other periods was in a stable state,turbulence effect was weak and the sensible heat flux was small.