# Presentation: 763319

## South Carolina Forestry Commission

- March 7, 2006
- 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 two prescribed burns (Molly’s Rock (713 acres) and Henderson Island (400 acres)) conducted by the South Carolina Forestry Commission. The burns were conducted on 7 March 2006. The model simulations run from 1600 EST 7 March through 0800 EST 8 March. This case was run with a 90 m grid. The site was located within the Piedmont of north-central South Carolina.
- Field personnel operated throughout the night beginning at 2245 EST 7 March through 0700 EST 8 March to observe smoke.

## Weather

- Weather during the burn and the post-burn smoke movement period was mostly clear. A weak low pressure trough extended from the lee of the mountains of North Carolina over the Piedmont of South Carolina. This system produced generally variable winds and weak synoptic forcing over the burn site. This pattern persisted throughout the analysis period. The geostrophic wind speed, a measure of the strength of the forcing by the large scale (synoptic) wind field was mostly less than 4.0 m/sec. This weak forcing would not oppose the formation of drainage flows in Piedmont terrain but would reinforce drainage flows running from the southwest to the northeast.

## Modeling Information

- PB-Piedmont Version 5.0-2006
- Grid spacing = 90 m
- Domain size = 492x480 -> 44.3x43.2 km
- Visual domain = 24.8x26.2 km
- Weather data: Hourly METAR
- Elevation data: USGS 30 m DEM
- Elevation contour interval = 11 meters
- Elevation range is 68-198 meters

## The full 44.3x43.2 km model domain captures most of the branched drainage system north of the Henderson Island burn site (white square). However, the main valley continues north off the grid. 

- The full 44.3x43.2 km model domain captures most of the branched drainage system north of the Henderson Island burn site (white square). However, the main valley continues north off the grid.

## The PB-Piedmont viewing domain and observation sites for 7 March 2006. The yellow polygons enclose the 400 acre Henderson Island burn site (Point 3) and the 713 acre Molly’s Rock burn site south of Point 17. Smoke observations were taken at several times during the night at some of these sites.

## The threaded plume structure typical of PB-Piedmont simulations when local winds caused by incipient drainage flows interact with the synoptic wind. Note that the wind blows from the north-northwest, directly down-valley from the Henderson Island site. The time is 1900 EST, 39 minutes after sunset.

## 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 analysis & observations 2300 EST (11 PM) 7 March 2006

- 15: Smoke smell (2245)

- 16: Light smoke (2250)

- 17: Thick smoke (2253)

- 18: Light smoke (2255)

- 19: Smoke smell (2257)

- 20: No smoke 2301)

- Click left mouse button to view observation points.

- 21: No smoke (2311)

- 22: No smoke (2316)

- 23: Smoke smell (2318)

- 24: Light smoke (2320)

- 26: Light smoke (2330)

- 27: No smoke (2333)

- 25: Light smoke (2325)

- 5: No smoke (2340)

## Summary: 2300 Observations

- Observations taken from 2245-2340 were compared with the 2300 PB-Piedmont simulation.
- PB-Piedmont correctly placed smoke or no smoke at 10 of the 14 observation sites.
- Smoke observed at Points 18 & 19 was from the daytime plume that had drifted SE then became entrapped after sunset.
- Red dots locate where fog and smoke could coexist.
- Model did not simulate smoke where it was observed at Points 25 & 26.

## 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 analysis & observations 0100 EST 8 March 2006 

- PB-Piedmont analysis & observations 0100 EST 8 March 2006

- 6: Smoke (0048)

- 7: No smoke (0051)

- 8: No smoke (0100)

- 9: No smoke (0000)

- 10: No smoke (0005)

- 11: No smoke (0007)

- Click left mouse button to view observation points.

- 12: No smoke (0015)

- 13: No smoke (0035)

- 14: No smoke (0115)

- 16: Slight smoke (0043)

- 18: Light smoke (0038)

- 19: Slight smoke (0037)

- 17: Thick smoke (0041)

## Summary: 0100 Observations

- Observations taken from 0037- 0115 EST were compared with the 0100 PB-Piedmont simulation.
- PB-Piedmont correctly placed smoke or no smoke at 9 of the 13 observation sites.
- Smoke was not observed at Points 9, 10, & 11 even though prevailing synoptic winds carried smoke down valley before sunset. No drainage flow carried smoke that far.
- Red dots locate where fog and smoke could coexist.

## 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 analysis & observations 0600 EST 8 March 2006 

- PB-Piedmont analysis & observations 0600 EST 8 March 2006

- 5: No smoke (0615)

- 6: Light smoke (0630)

- 7: Light smoke (0625)

- 8: Light smoke (0635)

- 9: No smoke (0540)

- 13: Smoke (0655)

- Click left mouse button to view observation points.

- 14: Light smoke (0702)

- 15: Light smoke (0635)

- 16: Light smoke (0631)

- 17: Thick smoke (0645)

- 19: Smoke (0510)

- 20: Light smoke (0500)

- 18: Smoke (0650)

## PB-Piedmont analysis & observations 0600 EST 8 March 2006 

- PB-Piedmont analysis & observations 0600 EST 8 March 2006

- 21: Smoke (0520)

- 22: Light smoke (0545)

- 23: Light smoke (0550)

- Click left mouse button to view observation points.

- 24: No smoke (0555)

- 25: No smoke (0600)

- 26: No smoke (0605)

- 27: No smoke (0610)

- 29: Light smoke (0658)

- 30: Light smoke (0700)

- 28: Light smoke (0640)

## Summary: 0600 Observations

- Observations taken from 0500- 0702 EST were compared with the 0600 PB-Piedmont simulation.
- PB-Piedmont correctly placed smoke or no smoke at 12 of the 23 observation sites.
- Observers reported smoke at Points 13, 14, 20, 29, 30 south and southeast of the southwestern burn site. Synoptic forcing did not favor smoke movement into this area. However, movement of smoke to Points 8 & 15 and departure of smoke from Points 24 & 25 does suggest that local circulations pushed the smoke southwest and south sometime between 0100 and 0600 EST. None of the observed hourly weather data supported this assertion.

## Summary:

- PB-Piedmont correctly placed smoke or no smoke at only 31 of the 50 observation sites.
- Observers reported that the Henderson Island site is burned every year and therefore there is not much fuel there. That could be a reason why no smoke was observed at any of the Points connected with the Henderson Island burn.
- Synoptic forcing never supported the observations of smoke south of the Molly’s Rock burn. An explanation is the transport of smoke from a distant burn to the south into the area.
- Another explanation is that local circulations not picked up in the hourly weather data carried smoke south of Molly’s Rock. Drainage forcing would have opposed smoke movement by such circulations.

## Smoke Matrix

- Smoke Prediction

- Yes                 No

- Smoke Observation

-   No                Yes

- 21

- 10

- 9

- 10