台灣山區扁柏林地可感熱、潛熱及二氧化碳通量特性之研究

Abstract

Second-order turbulence moments of wind velocities, temperature, water vapor, and CO2 observed with an eddy covariance system over a mountainous cypress forest are used to investigate the transportation of momentum and scalars between the atmosphere and the ecosystem. In this site, vertical wind velocity was found to follow the Monin-Obukhov similarity functions after separating the measurements with the uphill and downhill flow directions. We also found that temperature similarity characteristic constant consists with previous studies with a near unity value, while water vapor and CO2 require a Bowen ratio filtering procedure to get more reasonable values. The characteristic constants found were checked over with the flux-variance method, and fair to good results were noticed. For sensible heat flux, the general flux-variance equation works well. And For water vapor and CO2 fluxes, the representative relative transport efficiencies are preferred, while the characteristic constants found with Bowen ratio filtering method can also provide a fair estimation. Methods for the relation between relative transport efficiency and its correlation coefficient are also explored for water vapor and CO2 against temperature. A blurred relation is found for water vapor due to the complicated humidity field over the site, and a -0.5 power relation is introduced for CO2 when Bowen ratio is higher than unity.