Forest-Air Fluxes Of Carbon, Water And Energy Over Non-Flat Terrain

Authors: Lee X.¹; Hu X.²

Source: Boundary-Layer Meteorology, Volume 103, Number 2, May 2002 , pp. 277-301(25)

Publisher: Springer

Abstract:

A field study of surface-air exchange of carbon, water, and energy was conducted at a mid-latitude, mixed forest on non-flat terrain to investigate how to best interpret biological signals from the eddy flux data that may be subject to advective influences. It is shown that during periods of Southwest winds (sector with mild topography), the eddy fluxes are well-behaved in terms of energy balance closure, the existence of a constant flux layer, consistency with chamber observations and the expected abiotic controls on the fluxes. Advective influences are evident during periods with wind from a steep (15%) slope to the Northeast of the tower. These influences appear more severe on CO_2 flux, particularly in stable air, than on the energy fluxes. Large positive flux of CO_2 (> 23 mol m^-2 s^-1) occurs frequently at night. The annual sum of the carbon flux is positive, but the issue about whether the forest is a source of atmospheric carbon remains inconclusive.

Attempts are made to assess vertical advection using the data collected on a single tower. Over the Southwest sector, vertical advection makes a statistically significant but small contribution to the 30-min energy imbalance and CO_2 flux variations. Contributions by horizontal advection may be larger but cannot be verified directly by the current experimental method.

Keywords: Advection; Carbon cycle; Eddy covariance; Energy balance; Evaporation; Mixed forest; Rolling topography

Language: English

Document Type: Regular paper

Affiliations: 1: School of Forestry and Environmental Studies, Yale University, 370 Prospect Street, New Haven, Connecticut 06511, USA E-mail: xuhui.lee@yale.edu 2: School of Forestry and Environmental Studies, Yale University, 370 Prospect Street, New Haven, Connecticut 06511, USA

Publication date: 2002-05-01

• In this: publication
• By this: publisher
• In this Subject: Geophysics & Geomagnetism ,  Meteorology & Climatology ,  Hydraulic & Environmental Engineering
• By this author: Lee X. ;  Hu X.

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