Private Landowner Smoke

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Private Landowner Smoke

• 25 January 2003
• PB-Piedmont Version 3.0
• Smoke Simulation Analysis
• Gary L. Achtemeier
• USDA Forest Service
• Athens, GA

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Event Description
On 25 January 2003, a private landowner burned 20
acres of timberland in central Georgia. The fire
was ignited at 1100 and firing ended at 1440 EST.
Smoke blew to the east during the burn. At 1900
(700 PM), one hour after sunset, the landowner
walked the perimeter of his burn site and found
no smoke coming off the west, south, or east
edges. He found smoke coming off the entire
length of the north edge. The problem for
PB-Piedmont is to simulate smoke moving east
during the afternoon and smoke moving north after
sunset.
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Terrain and Weather
The burn site is located on a ridge with slopes
to the west, east and north. This was a
synoptic-driven event for two reasons. First,
the synoptic scale pressure forcing remained
strong for the period. Surface geostrophic wind
speeds, a measure of the strength of synoptic
scale forcing, ranged from 7.5 10.0 m/sec.
Geostrophic winds usually must drop below 5.0
m/sec for drainage winds to have much effect.
Second, clouds moved in shortly after sunset.
Surface weather data showed rapid transition from
scattered clouds before sunset to broken/overcast
conditions one hour after sunset. Cloud cover
impedes outgoing radiation and weakens drainage
forcing.
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Modeling Information

• PB-Piedmont Version 3.0-2003
• Grid spacing 60m
• Domain size 204x202 -gt 12.2x12.2 km
• Visual domain 1.6x1.6 km
• Weather data Hourly METAR
• Elevation data USGS 30 m DEM

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25 January 2003, 1800 EST Private Landowner
Burn 20 Acres
The burn site sits on the tip of a northward
protruding ridge. In the color scheme, dark green
represents low valleys and whites represent
highest ground. The elevation difference between
valley and ridge is 50 m. 20 acre burn area
outlined by blue square. Smoke, indicated by
yellow squares drifts to the east.
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25 January 2003, 1900 EST Private Landowner Burn
20 Acres
PB-Piedmont smoke simulated for 1900 EST (7PM)
when landowner reported smoke moving across
northern boundary of plot only.
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25 January 2003, 2100 EST Private Landowner Burn
20 Acres
PB-Piedmont smoke simulated for 2100 EST (9PM), 2
hours after landowner reported smoke moving north
off burn site.
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Simulation Summary
The landowner reported winds blowing from the
west during his burn but shifting rapidly to blow
from the south by one hour after sunset (7PM).
PB-Piedmont was slower in simulating the wind
shift, having turned the winds to blow almost
from the south by 9PM.