# Presentation: 788383

## Piedmont National Wildlife Refuge

- January 22, 2004
- Smoke Simulation Analysis
- Gary L. Achtemeier
- USDA Forest Service
- Athens, GA

## Task Description

- The following set of slides summarize a PB-Piedmont post-burn analysis of smoke movement in the aftermath of a 908 acre prescribed burn conducted by the Piedmont National Wildlife Refuge. The burn was conducted on 22 January 2004. The model simulations run from 1700 EST 22 January through 0800 EST 23 January.

## Synopsis

- The case of 22 January 2004 is instructive as it violates a basic assumption made in the development of PB-Piedmont – namely that the drainage layer decouples from the air above it. This assumption is violated under strong winds when turbulent mixing breaks up the drainage layer and mixes out the smoke. PB-Piedmont does not allow for mix-out of smoke and thus predicts smoke where smoke does not occur.

## Weather

- Weather during the burn and the post-burn smoke movement period was clear and dry. A high pressure system to the west of the burn site in combination with a strong low well to the northeast favored winds blowing from the northwest during the whole period of the simulation. The geostrophic wind, a measure of the intensity of the synoptic pressure driving the winds, was the strongest yet calculated for the PB-Piedmont validation studies. It ranged from 14.3 to 18.7 m/sec, meaning that wind gusts in excess of 40 mph were possible on this night.

## Modeling Information

- PB-Piedmont Version 3.0-2003
- Grid spacing = 60m
- Domain size = 303x299 -> 18.2x17.9 km
- Visual domain = 13.3x10.1 km
- Weather data: Hourly METAR
- Elevation data: USGS 30 m DEM

## Modeling Information

- The next slide shows the PB-Piedmont viewing domain for the 22 January 2004 smoke simulation. The model burn area is shown by the blue square. The actual burn area is outlined by the white polygon. Smoke observations taken from 0600 –0700 LST by Fish & Wildlife Service personnel are located by the blue circles. The model smoke plume at 1800 LST for the 10 m surface layer is shown by the yellow dots.

## PB-Piedmont domain, roads, observation points 1800 LST 22 January 2004

## Smoke Location Evaluation:Interpreting the Observations Shown in the Next Slide

- Red symbol means smoke observed
- Green symbol means smoke not observed
- Circle means model matched observation
- Triangle means model unsuccessful

## PB-Piedmont observation points 0700 LST 22 January 2004

- 5: No smoke (0612)

- 6: No smoke (0620)

- 7: No smoke (0626)

- 8: No smoke (0631)

- 9: No smoke (0637)

- 10: Light smoke (0641)

- 11: Light Smoke (0648)

- 12: No smoke (0708)

- Click left mouse button to view observation points.

## Summary:

- Green triangles – Strong mixing due to high winds is believed to have removed smoke in any significant concentrations from these locations.
- Red triangle – The western edge of the actual burn site was located west of the square used by PB-Piedmont. Thus no smoke was produced at this location by the model.
- This case of strong synoptic forcing (strong winds) violated the drainage layer entrapment assumption of PB-Piedmont. This kind of event causes the model to produce a “false alarm” – meaning, predicting smoke on the ground when smoke is not observed.