Minutes of the January 24, 2005 Meeting
Smoky Mountain AMS Chapter
Thirteen folks attended last night's meeting. We ate at the Tennessee Grill and afterward had a very interesting presentation by Dr. Bai Yang of ORNL titled "Turbulent Flow Across a Forest Edge: An Application of Large Eddy Simulation". Bai did a great job of helping us non-specialists understand the basic dynamics of this micrometeorological scenario, which is very interesting in a theoretical sense, but also has important applications in the area of determining the placement of meteorological towers for measuring various things such as fluxes of CO2 within the forest canopy. This relates to an important national global change project called Ameriflux, whose home page is on the CDIAC site at ORNL: http://public.ornl.gov/ameriflux/
A few notes from Dr. Bai Yang are as follows:
"Large eddy simulation (LES) has been a powerful numerical tool in studying turbulent flow for a few decades. It was initially used by engineers and later adopted by meteorologists in the 1970s. Within the last 20 years or so, its application on micro-scale processes in the atmospheric boundary layer has bloomed; for example, turbulent flow in the planetary boundary layer, low level clouds over marine surfaces, turbulent flow within tall vegetation layers (forests) and over complex terrain (hills), and pollutant dispersion in urban areas.
In this talk I will present my PhD research with a focus on some interesting results from LES data, rather than the theoretical details of the model. In my case, LES was used to simulate turbulent flow across a forest edge. As the first step, the model was validated by comparing statistics from the simulated flow to field and wind tunnel measurements (but I may skip many figures in this part). Secondly, LES data with high resolution in both time and space, allowed me to look into the momentum and turbulent kinetic energy (TKE) budgets in detail. Such a detailed analysis would normally be difficult from field measurements due to infeasibility of setting up an intensive network and difficulty in achieving some terms (for example, dynamic pressure). Thirdly, bending moments at the base of the trees were estimated and analyzed to address the issue of tree damage. The last, but most interesting part of my work was to identify coherent structures in the turbulent flow. A coherent structure consists of a micro-front, a sweep and an ejection motion, and is mainly responsible for momentum and mass transportation in canopy flow. A micro-front shares many similarities to the synoptic scale fronts we see everyday on weather maps. (I may spend a little more time on this last part.)"
Thanks again to Bai for volunteering to speak to us. Thanks also to Ed Dumas who brought his camera with him to capture some shots of the meeting and presentation for website/poster use.
One other note from last night's meeting. Since our chapter books are in really great shape (but hey, don't think you don't need to pay your $10 dues at the March meeting! - kudos to Forrest and perhaps others who settled up right away last night), a motion was made and approved by voice vote that would allow our judges (T.J. Blasing and Ray Hosker) at this April's Southern Appalachian Science and Engineering Fair to, at their discretion, award not just one, but two awards to outstanding projects relating to meteorology. Each award is a $100 U.S. Savings Bond (cost of $50 per bond).
Also, Joanne Logan brought up the possibility of getting the word out to East Tennessee school systems (for the 2006 science fair season and beyond) that our chapter would be willing to provide modest financial support to students who may have a meteorologically-oriented project in mind, but may find it difficult to afford buying materials for the project. We had in mind students that may have some real enthusiasm for a an ambitious project but would nonetheless have trouble coming up with the $20, $30, or $40 they might need for materials. There are certainly plenty of kids in East TN where that would be a financial burden. We need to stay on top of this idea through using the listserver and discussion at our meetings so that we can come up with an effective way to get the word out on this. Please share any knowledge of how we can accomplish this communication and be giving thought to the basic criteria we will need to formulate pertaining to giving such assistance (e.g., what to require from the student as far as project idea information or other information).
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