# Presentation: 743625

## Piedmont National Wildlife Refuge

- March 24, 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 569 acre prescribed burn conducted by the Piedmont National Wildlife Refuge. The burn was conducted on 24 March 2004. The model simulations run from 1600 LST 24 March through 0700 LST 25 March.

## Weather

- Weather during the burn and the post-burn smoke movement period was clear and dry. A strong high pressure system located east of the area maintained a strong pressure gradient that directed winds to blow from the east on 24 March and then more from the northeast on the morning of 25 March. This high gradually built westward during the night and the pressure gradient decreased somewhat. Geostrophic winds, a measure of the strength of the synoptic scale pressure field, decreased from 10 m/sec at 1600 LST 24 March to 6 m/sec at 0500 LST 25 March. Thus weather conditions became more favorable for drainage flow formation later in the period.

## Modeling Information

- PB-Piedmont Version 3.0-2003
- Grid spacing = 60m
- Domain size = 325x430 ->19.5x25.8 km
- Visual domain = 14.8x11.6 km
- Weather data: Hourly METAR
- Elevation data: USGS 30 m DEM

- Smoke Behavior
- The points numbered 5-11 identify locations along roads (blue lines) where smoke was observed by PNWR personnel between 0612 – 0644 LST 25 March 2004. The actual burn area is outlined by the orange polygon. PB-Piedmont uses the white square. Streams of yellow dots at 1800 LST identify the 10 m deep surface layer smoke plume.

- Smoke Behavior
- By 2000 LST, drainage forcing is entrapping the remnants of the daytime plume in the valleys. Drainage forcing and synoptic forcing reinforce along the west-east oriented valley between points 8 and 10.

- Smoke Behavior
- By midnight (0000 25 March 2004), remnants of the daytime plume remain scattered over basins west of the burn site. Meanwhile, drainage flows have carried smoke from the burn site down the length of the the Falling Creek valley.

## 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
- Light Smoke – smoke visible but no concern for drivers
- Moderate Smoke – smoke dense enough to slow traffic but not stop it

## Smoke observation points 0700 EST 25 March 2004

- 5: No smoke (0612)

- 6: Moderate smoke to 7: (0619-0623)

- 8: Very light smoke from 7 to here (0628)

- 9: Smoke boundary (0637)

- 10: No smoke (0644)

- 11: Light smoke (time unknown)

- Click left mouse button to view smoke observation points.

## Summary

- Point 5 was located at the top of a high point on the ridge. The model placed dense smoke around Point 5 and light smoke at Point 5. Thus the model placed smoke where smoke was not observed.
- Points 6-7 straddle Point 5 on the same ridge. The observer reported moderate smoke all along the road with greatest amounts in ridge gaps. Point 6 was the easternmost point of the burn unit as shown in slide 5. It is noteworthy that the observer reported no smoke at Point 5 at 0612 yet no mention of the lack of smoke there is made during the period of smoke observation along the road from Points 6-7 (0619-0623). Furthermore, there was no smoke at Point 5 at 0600 LST.

## Summary

- Point 8: The observer reported very light but visible smoke continuously from Point 7 to Point 8. The model shows a few smoke intrusions to the road with most continuous smoke in the vicinity of Point 8. There were no reports (yes or no) of smoke beyond Point 8.
- Point 11 is the location of the home of a Refuge employee. He reported smoke at his house “in the morning”. The model moved residual smoke from the old daytime plume into that area by morning thus giving the “inference” that smoke was correctly predicted there. However, the coverage of points was too thin to warrant a call of smoke. Thus the model failed to predict smoke at Point 11 where smoke was observed.

## Summary

- This study gives another example of the successes and limitations of PB-Piedmont. Two limitations are apparent. First, the model places the burn unit boundaries as a square whereas the burn unit was highly irregular with part extending up the road to Point 6. Second, this version of the model does not include land use. Note that the road was oriented generally along a NE-SW axis. Once smoke from the burn site got on the road near Point 6, it was possible for synoptic forcing to push it down the road to Point 8. PB-Piedmont currently does not provide for flow down road cuts.