Development of a Measuring System for Surface Energy and Water Vapor Fluxes at Large Scale

Based on the extension of the first-order perturbation theory of optical scintillation and Monin-Obukhov similarity theory,an apparatus YZ01 for measuring the refractive index structure constant C2n and for measuring surface fluxes,such as sensible heat flux and latent heat flux along a long line-of-sight path,was developed.This apparatus consists of a transmitter part,a receiver part,an optical alignment part and a signal processing part.Signal modulation and demodulation method is used to distinguish the EM signal from background radiation.Filter and feedback circuitry is used to increase signal to noise ratio.The power of YZ01 transmitter is 3W average,and the receiver only 1.8W.The feature and accuracy of YZ01 was tested by comparing with Kipp Zonen LAS and Scintec BLS450 over Miyun site,Beijing and Arou site,Qinghai.The results showed: ①The modulate signal of YZ01 is about 14% stronger than KippZonen LAS over Miyun site.②The slope of linear regression and the correlation coefficient of C2n between YZ01 and LAS is 0.98 and 0.7 over Miyun site.③The slope of linear regression and the correlation coefficient of H between YZ01 and LAS is 0.90 and 0.93 over Miyun site.④The slope of linear regression and the correlation coefficient of LE between YZ01 and LAS is 1.07 and 0.78 over Miyun site.⑤The slope of linear regression and the correlation coefficient of C2n between YZ01 and BLS450 is 1.25 and 0.93 over Arou site.⑥The slope of linear regression and the correlation coefficient of H between YZ01 and BLS450 is 1.17 and 0.99 over Arou site.⑦The slope of linear regression and the correlation coefficient of LE between YZ01 and BLS450 is 1.03 and 0.84 over Arou site.