# Presentation: 785672

## Piedmont National Wildlife Refuge

- January 21, 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 886 acre prescribed burn conducted by the Piedmont National Wildlife Refuge. The burn was conducted on 21 January 2004. The model simulations run from 1600 EST 21 January through 0800 EST 22 January.

## 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 day of the 21st. The high remained to the west and the low intensified thus increasing the pressure gradient over central Georgia. The geostrophic wind, a measure of the intensity of the synoptic pressure driving the winds, increased from 4.1 m/sec at the beginning of the period to 14.4 m/sec at the end of the period. Observed winds blew from the WNW all night at speeds of approximately 3 m/sec. This case is one of steady, dominant synoptic forcing opposing drainage flow formation throughout the duration of the study period.

## Modeling Information

- PB-Piedmont Version 3.0-2003
- Grid spacing = 60m
- Domain size = 337x407 -> 20.2x24.4 km
- Visual domain = 16.7x15.2 km
- Weather data: Hourly METAR
- Elevation data: USGS 30 m DEM

## Modeling Information

- The next slide shows the PB-Piedmont viewing domain for the 21 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 21 January 2004

## Modeling Information

- The next slide shows the PB-Piedmont viewing domain for 2300 LST 21 January 2004. The period from sunset to midnight is when synoptic forcing from the west is weakest. Synoptic forcing opposes drainage forcing on valleys lying on a general east-west axis and draining to the west. The original smoke plume settles into the basins and is entrapped. Meanwhile drainage flows in valleys oriented generally north-south are unopposed by synoptic forcing. Drainage flows along the north-south fork of Falling Creek carry smoke southward to where the valley turns west (arrow).

## PB-Piedmont observation points 2300 LST 21 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 (0615)

- 6: Light smoke (0622)

- 7: Light smoke (0625)

- 8: No smoke (0628)

- 9: Light smoke (0633)

- 10: Light smoke (0636)

- 11: Smoke (0638)

- 12: Light smoke (0644)

- 13: Light smoke (0648)

- 14: No smoke (0655)

- 15: No smoke (0703)

- Click left mouse button to view observation points.

- 16. No smoke (0708)

- 17. No smoke (0711)

## Summary:

- Points 6 and 7 were located on a ridge above the west fork of Falling Creek. The observer reported light smoke. Given the strength and direction of the synoptic forcing, PB-Piedmont never placed smoke at these locations. Further, one is inclined to look for smoke from some other source located to the west of these sites.
- Point 8 was located where a road crossed Falling Creek drainage where it turned west. The observer reported no smoke. PB-Piedmont brought smoke into this area early. Later, stronger synoptic forcing dispersed smoke from this area. A few points remained in the area of the stream by 0600 LST. Point 8 could have been called either way – a model success or a model failure.

## Summary:

- Point 14 was located at a road junction on a high elevation peak. The observer reported no smoke here. On close inspection, PB-Piedmont produced no smoke at that location. PB-Piedmont is successful at flowing smoke through gaps in ridges. The model did place smoke on both sides of the ridge and crossing the roads surrounding this location. Given the model’s record at guiding smoke around high points, I accorded the model a success at Point 14.
- Point 15 was located at a road junction along a long flat ridge east of the burn site. Point 15 was directly downwind from the burn site – at least as simulated by PB-Piedmont. The model placed smoke in the surrounding drainages, an inference that smoke was being or had been transported over Point 15 albeit in very low particle concentrations. No smoke was observed at Point 15

## Summary:

- Points 6 and 7 were the greatest puzzle as regarding the presence of smoke. If the smoke at these locations originated from the burn site, then no explanation can be offered for the failure of PB-Piedmont to place smoke there given the strength of the synoptic forcing.
- Smoke presence or absence at several other locations was problematic.