# Presentation: 679048

## The Smoke Plume of 06 March 2002. A Possible Test Case

- Gary L. Achtemeier
- USDA Forest Service
- Athens, GA

## Case Description

- On March 6, 2002, the Oconee National Forest and the Piedmont National Wildlife Refuge conducted prescribed burns in central Georgia. It is estimated that the total acreage was 1500 acres burned. Records are available regarding exact acres burned, fuel type, and possibly fuel loadings.
- As part of the SRS Smoke Project, a fixed wing aircraft on loan from the Georgia Forestry Commission was outfitted with an ensemble of thermocouples and flown in close proximity to the burns from shortly after ignition until about 1700 LST. Four vertical ascents yielding eight temperature soundings were obtained along with 30 digital images of the plume.

## The next slide gives information on the temperature sensors used for the study. Then the following two slides show the aircraft used and the location of the sensors on the landing gear strut.

## Thermocouple Sensor Description

- Copper – Constantan
- Duplex insulated
- Coarse wire – 24 gauge, diameter=0.02” (0.05 cm)
- Fine wire – 36 gauge, diameter =0.005” (0.013 cm)

## GFC aircraft used for the Smoke Project. Instruments will be attached to the footpad on the strut and cables run into luggage door. 

- GFC aircraft used for the Smoke Project. Instruments will be attached to the footpad on the strut and cables run into luggage door.

## Thermocouple sensors. Two coarse wires are visible extending from straw. Two fine wires are adjacent.

## 06 March 2002 Smoke Flight

- Location: Oconee National Forest and Piedmont National Wildlife Refuge – 2 sites
- Acres burned: Approximately 1,000 – 1,500 acres combined.
- Weather – clear, winds from south steady all day
- The next slide shows the flight tracks and photo sites overlain on an elevation map of the area as obtained from the GIS module of the smoke model PB-Piedmont.

- To Athens

- Milledgeville

- The three flight legs for the 06 March 2002 smoke plume recon flight. White (first leg), red (second leg) and blue (third leg). Yellow square identifies burn site; plume by dashed yellow lines. Photos located and numbered.

- 100 km

- 80 km

## Details of flight paths and photo locations in the immediate vicinity of the burn site. 06 March 2002

## Burn A is in the foreground. Burn B is in the background. Arrows show probable backfire lines for Burn B. Clock time at the lower right is in GMT. Local time is 1145AM. Note that this burn could be represented by several individual plumes.

## Burn A is in the foreground; Burn B is in the background. This is a “mass-ignition” burn designed to develop a warm convective plume that will carry the bulk of the smoke above the ground.

## Burn A develops a strong convective plume

## The next slide shows the altitude track for the first flight track. The vertical ascent and descent to develop vertical temperature profiles was done just southwest of the plumes. The dots identify where along the altitude track digital images of the plume were taken.

## and altitudes of photographs

- 1145               1200                 1215                1230

## Burn B in foreground and Burn A in background. Aircraft descending to line up plume top with horizon to determine height of plume.

## Convective plume of Burn B overshoots into stable air above the mixing layer.

## The next slide shows the vertical temperature profile for both ascent and descent for Flight Leg 1. The dashed orange line identifies the slope of a dry adiabat – the temperature profile for neutral stability and an identifier for the well-mixed boundary layer. The aircraft is flying within the boundary layer at all altitudes where the slope of the measured temperature profiles is approximately equal to the slope of the dry adiabat.

## Complete sounding for Flight Leg 1. Orange dashed line is “dry adiabat” temperature profile for neutral mixing. Top of the smoke plume is identified by the dashed line at 2000 m. Grey area identifies error bounds in the altitude of the top of the smoke plume as measured by sighting the plume top with the horizon. Dashed line box identifies depth of the atmosphere above the mixed layer that contains smoke.

## The next slide shows the altitude track for the second flight track. Two ascents were made giving four vertical temperature profiles near the smoke plume. These soundings were taken about 30km downwind (northeast) of the burns. The dots identify where along the altitude track digital images of the plume were taken.

## and altitudes of photographs

- 1400     1415     1430     1445      1500      1515

## The leading edge of the plume at 1416 EST. Faint streamers may be precipitation of larger particles or erosion of plume by deepening convective mixing layer.

## Looking West at 1417 EST. Elevated dense smoke appears as a dark band.

## Looking Southwest at 1419 EST toward Burn A. The top of the plume is lined with the horizon to estimate plume top height for Sounding 1 of Flight Leg 2. Note how the plume is in transition from strongly convective to lying near the ground.

## The first sounding for Flight Leg 2. Dashed line at 2220 m identifies measured plume height. The gray area identifies probable error bounds in the measurement. The depth of the plume contained in the atmospheric layer above the mixed layer is approximately 700 m.

## Same as previous slide except for Sounding 2. The height of the top of the plume is the same but note that the depth of the mixed layer extends to 1900 m 

- Same as previous slide except for Sounding 2. The height of the top of the plume is the same but note that the depth of the mixed layer extends to 1900 m

## Apparent vigorous mixing near the leading edge of the plume at 1445 EST.

## and altitudes of photographs

- 1630              1645              1700           1715

## The temperature sounding for Flight Leg 3. Plume top was found near 2400 m. Ascent continued to 2909 m as aircraft flew over top of plume for photo-documentation of edge structures. The following slides show the eastern and western edges of the plume.

## The eastern edge of the plume from 2900 m. Note the well-defined boundary.

## The western edge of the plume

## Summary

- Approximately 30 percent of the plume is contained in the atmosphere above the mixing layer.
- A sizeable fraction of the plume mass may be contained in the higher layer.
- There was apparent erosion of the plume base by a deepening mixing layer and/or precipitation of larger particles from the plume.
- Plume boundaries are observable thus making it possible to estimate horizontal spread.

## The final slide shows a photograph taken from the ground looking to the southeast. The time is near sunset (1800 LST). The photograph shows the smoke plume approaching the Athens, GA, area, approximately 100 km northeast of the burn site. 

## Slide 33