Many experiments have been performed in forests to improve estimations of net ecosystem exchange(NEE) of CO2. A thorough knowledge of the exchange of CO2 between forests and the atmosphere is essential in order to understand the role of forest ecosystems in the global atmospheric CO2 budget. Because ideal homogeneous surface is rarely seen at the earth’s surface, neglect of advection due to surface inhomogeneity can lead to systematic errors in NEE measurements.

An intensive experiment was carried out in a 65 m tall, 400-600 year old coniferous temperate rain forest in Southern Washington, a long-term AmeriFlux measurement site, to determine the micrometeorological components contributing to NEE. An 83 m high tower-crane facilitates the collection of micrometeorological data along a vertical profile, with air temperature, wind speed and direction, and photosynthetically active radiation. Mean concentrations of water vapor and carbon dioxide were measured at eight heights in the vertical, and in nine horizontal locations at the 2 m and 30 m heights, to assist in estimation of the mean advection and storage terms in the NEE equation. Eddy-covariance of vertical water vapor and CO2 fluxes are measured at 3 m and 70 m using 3-D sonic anemometers and fast- response gas analyzer(IRGA) at frequency of 10 Hz. The data are averaged in every 30 minutes for year 1999-2001. The advection relative to eddy-covariance is examined for daytime, nighttime, and seasons, respectively. Our results imply that mean advection components can be major contributors to the carbon budget estimates within and above forest ecosystems.