ADVANCES IN THE STUDY OF AREAL SURFACE FLUXES WITH LARGE APERTURE SCINTILLOMETER

It is very important to determine land surface fluxes, including sensible heat fluxes and latent heat fluxes, for the issues involving many aspects of climate, agriculture, hydrology, and water resources management. However, it is still very difficult to observe and study areal fluxes in the scale of several to tens kilometers, especially on heterogeneous land surface. The Large Aperture Scintillometer (LAS), which is becoming popular in recent years, offers a new perspective to solve this problem. Based on light scintillation in the turbulent atmosphere,it can measure sensible heat fluxes by emitting a beam of light over a horizontal path. Then, latent heat fluxes can be derived according to surface energy balance equation. The LAS is adapted to different kinds of land surface, homogeneous or heterogeneous. Test comparisons of LAS flux measurement with the measurements by eddy correlation system show good agreement. There are some key factors, which influence the precision of areal evapotranspiration determined by LAS, such as beam height, wind speed, roughness length, zero plane displacement, Bowen ratio, and net radiation, etc. Basic principle and some algorithms are introduced. A prosperous utilization of LAS in recent years is in the validation of areal surface fluxes retrieved from remote sensing models, such as the SEBAL and SEBS. Finally, this paper discusses the development trend of applying the large aperture scintillometer in the future.