Upscaling Parameterization of Sensible Heat Flux under Different Atmospheric Stability Conditions across Various Land Surface Types

• Main Authors: Chao-Jung Fan, 范釗榮
• Other Authors: Jehn_Yih Juang
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/47850399742706646333

碩士 === 國立臺灣大學 === 地理環境資源學研究所 === 100 === Abstract Eddy-covariance (EC) system has been used to measure exchange of scalars, momentum and energy components between land surface and atmosphere in the past decades. But the limitations and assumptions of EC method such as being a point-measurement make EC method uncertain over complex terrain. To systematically quantify area-averaged energy fluxes, comparing between energy fluxes measured by EC method and surface-layer scintillometer (SLS) over hilly terrain and estuarial grass marsh is studied in this research. SLS system applied Monin-Obukhov Similarity Theory (MOST) to estimate sensible heat fluxes by linking variances and covariances of laser beam intensity within path-length between laser transmitter and receiver and SLS system was established at Xitou flux tower during summer and winter, and at Guandu Nature Park during winter. Owing to the measurement within path-length, SLS system provides better spatial representative than conventional tower-based EC results. In this study, surface parameters and properties such as friction velocity, Bowen ratio and surface roughness length are investigated to understand the features of turbulence formation in each site. Results suggest the under-estimated sensible heat flux by scintillometer and an explanation to the difference of measurement is established under various atmospheric conditions. In this study, it’s concluded that at Xitou, SLS measures about 0.35 times of sensible heat flux to that by EC under stable state and the correlations y=0.76x2-0.56x+1.76 and y=1.56x2-2.07x+1.81 could describe the relationship between logarithm of stability and H ratio under unstable state in winter and summer respectively. At Guandu, the H ratio is constantly 0.9 under stable state and in correlation y=3.25e-0.044x-2.14 between logarithm of stability and H ratio under unstable state. The relationship between results of EC and SLS could be a linkage among tower-based studies and high-scale methods such as remote sensing and be estimated to be a base to regional micrometeorological modeling.