Ecosystem Science Reports

Atmospheric Sciences

Project Title: A Comparison of Techniques to Estimate the Mixing Height

Completion Date: March 31, 2004

Investigators: Brad Snyder and Timothy Ashman, Aquatic and Atmospheric Sciences Division, Environment Canada, Pacific and Yukon Region

Study Overview

The mixing height is the height of the atmospheric layer adjacent to the ground over which pollutants or any constituents emitted within this layer or entrained into it, become vertically dispersed by turbulence. The deeper the layer, the more readily dispersed the pollutants will be. The objective of this investigation was to determine whether there were better methods than currently used in the Pacific Region of Environment Canada that could be employed to estimate the mixing height. Selected techniques for estimating the mixing height were compared, with the goal of finding the optimum for use in air quality forecast guidance.

Key Points for Decision-Makers

Key Scientific Findings

Key Points for Decision-Makers

• Improved methods for preparing the smoke management information forecast by Environment Canada's Pacific & Yukon Region have been found and recommended for implementation.

Key Scientific Findings

• The ‘true' mixing height was derived from Pacific 2001 Field Study ground-based lidar data. Various objective methods of estimating the mixing height from radiosonde measurements were used to compare against the lidar data. The technique currently used in forecast operations for estimating the mixing height was found to be deficient when compared with other methods. Improved techniques have been recommended for implementation in the smoke management guidance program in Environment Canada's Pacific & Yukon Region.

References

This report may be obtained directly from the author at brad.snyder@ec.gc.ca.

The correct citation of the paper is:

Snyder, B. and T. Ashman. 2004. A comparison of techniques to estimate the mixing height. Environment Canada, Pacific and Yukon Region, Vancouver, BC. eReport #2004-003. 2 April 2004.