| Summary: | 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.
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