Date of Award

2019

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Civil and Environmental Engineering

Supervisor

Xiaohong Xu

Rights

info:eu-repo/semantics/openAccess

Abstract

This study compared two bidirectional atmosphere-surface exchange models by Wang et al. (2014) and Wright & Zhang (2015) for one monitoring site in the state of Georgia in the United States of evergreen needleleaf forest and deciduous broadleaf forest in summer and winter. Input data includes observed GEM concentrations and simulated meteorological data from June 2010 to September 2010 and from December 2010 to March 2011. For evergreen needleleaf forest in summer, the net emission flux estimated by Wang’s model was greater than that by Wright & Zhang’s (0.5 pg m-2s-1 vs. 0.18 pg m-2s-1). For deciduous broadleaf forest in summer, the net emission flux predicted by Wang’s model was smaller than that by Wright & Zhang’s (0.1 pg m-2s-1 vs. 0.29 pg m-2s-1). However, regardless of land cover in winter, the net flux produced by Wang’s model was emission flux (0.21 pg m-2s-1 for evergreen needleleaf forest and 0.18 pg m-2s-1 for deciduous broadleaf forest) while that simulated by Wright & Zhang’s model was deposition flux (0.59 pg m-2s-1 for evergreen needleleaf forest and 0.49 pg m-2s-1 for deciduous broadleaf forest). Additionally, stomata resistance, in-canopy aerodynamic resistance, stomata emission velocity, GEM compensation point concentration in stomata, GEM compensation point concentration in soil, stomata emission flux, soil emission flux, and net flux had large differences (≥100%) between the two models. The dominant factors resulting in these differences were identified. Wright & Zhang’s model is more appropriate for simulating GEM exchange flux in winter when a net deposition flux is expected.

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