Study On Similarity Theory Applicability In Large Aperture Scintillometer Observation

As the growing concerning about the global climate change issues, and the development trend of researching scale for surface water flux and heat flux gradually shifting from point or patch scale to regional or global scale, Large Aperture Scintillometer (LAS) with the advantage of regional scale measurement has broad application prospects. However, there are still many problems, such as the applicability of similar theory (MOST), the stability of the universal function selection in LAS observations, which may affect the reliability of observational data. This study analyzed on the problem of the applicability of similarity theory based on the observational data in Guantao station and A’rou station, and proposed the operable methods to judge the applicability of similarity theory; obtained the most suitable stability universal function by Guyuan station observational data; discussed the uncertainties of LAS observation in the suburban non-uniform surface, and compared the results between Eddy-Covariance system (EC) and LAS observation. The main findings are as follows:(1) It was found that the applicability of MOST could be significantly affected by the large-eddy movement and the atmospheric turbulence development which based on the observational data in Guantao station2009and A’rou station2009(from January to July, from October to November). The applicability of MOST was worse when the large-eddy movement was more active (rwT is smaller), otherwise was better. The applicability of MOST is better under the unstable condition when the thermal turbulence was stronger (TT is larger), otherwise was worse. The temperature structure parameter method and the factor analysis method was developped to judge the applicability of MOST in LAS data processing. The former one was considered more suitable for conventional LAS data processing. The latter one was considered more suitable for basic theoretical research. Both two methods were confirmed to a certain improve the quality of LAS data.(2) It was found that atmospheric temperature structure parameter obtained by eddy correlation original data was consistent with obtained by large aperture scintillometer which based on the observational data in Guyuan station in June to September2011. The temperature structure parameter calculated by eddy correlation data was considered more suitable for fixing the stability universal function, the best stability universal function fT_Guyuan was also fixed. The function fT_Guyuan was proved to be reasonable and reliable by comparing different calculation methods for sensible heat flux. It was also found that the difference between fT_Guyuan and De Bruin (1993) was smallest, the difference between fT_Guyuan and Thiermann&Grassl (1992) was maximum, and the differences between them could be changed with the valiation of stability.(3) It was found that the effective height of Large Aperture Scintillometer (ZLAS) can significantly affected the estimated result of sensible heat fluxes which based on the observational data in Miyun station in2009. However, the influence of zero-plane displacement and surface roughness was small. It was also found that the sensible heat flux diurnal variation obtained by LAS in Miyun Station was smoother and with greater spatial representation when it compared to EC measurements. It was considered that the quality of observational data could be improved through raising the observation height, using similar theories judgment methods and suitable stability universal function.