| Summary: | 碩士 === 國立臺灣大學 === 環境工程學研究所 === 101 === The determination of atmospheric stability in the air quality models is considered to be one of the key issues to ensure the model performance. Sensible heat flux is an important parameter to quantity the atmospheric stability, which is usually obtained by point-based measurements, and used to quantity the air quality in specific region. However, the gap in spatial scales between the conventional station-measured data and the area-averaged estimation in the larger region makes the upscaling process of the sensible heat flux to be crucial in model simulation. Sensible heat flux measurements by different scale approaches might be distinct because of footprint areas and calculation process. This study measures sensible heat flux by using two different scale approaches: point-based eddy-covariance (EC) method and path-averaged surface layer scintillometer (SLS). SLS was established in winter at Guandu plant, a grassland surface with high moist. The results suggest that the under-estimated sensible heat flux and friction velocity by SLS and might cause by inactive turbulence. By investigating the relationship between sensible heat flux and meteorology parameters such as friction velocity and Bowen ratio would offer a good way to understand the influence of different spatial scale. Surface characteristics parameters such as Bowen ratio, albedo, and roughness length are used to determine sensible heat flux in AERMET, thus, it is important to determine surface parameters for simulations. Averaged Bowen ratio in the daytime are 0.55 and 0.42 which are determined by EC-measurements and SLS-measurements respectively which are different to default suggested from AERMET user’s guide. This study suggests that AERMET does not consider energy balance closure, it results in over-estimating sensible heat flux and then over-estimating ability of convection. For the future works, the calculation process for friction velocity in AERMET should be corrected and energy balance closure should be considered.
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