Fire Plume Rise WRAP FEJF Method vs' SMOKE Briggs SB Method

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Fire Plume RiseWRAP (FEJF) Method vs. SMOKE
Briggs (SB) Method

• Mohammad Omary, Gail Tonnesen
• WRAP Regional Modeling Center
• University of California Riverside
• Zac Adelman
• Carolina Environmental Program
• University of North Carolina

Fire Emissions Joint Forum Meeting, October
17-18, 2006, Spokane, WA
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Fire Plume Rise Modeling Project Status

• Todays Presentation
• Project Objectives
• Plume Rise Modeling Methods
• Fire Events Modeled
• Results
• Summary

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Acknowledgments

• Tom Moore and FEJF project design
• Air Sciences - Emissions Inventory

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Fire Plume Rise Modeling Project Objectives

• Compare the plume rise and the vertical emissions
  distribution for fires, using to methods
• The FEJF Approach
• The SMOKE-Briggs Approach

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Model vertical layer structure

• CMAQ has 19 vertical layers
• Layer 1 0 - 36 m
• Layer 2-5 36 - 220 m
• Layer 6-10 220 - 753 m
• Layer 11-14 753 - 1828 m
• Layer 15-16 1828 - 3448 m
• Layer 17-19 3448 - 14,662 m

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Plume Rise Modeling Methods

• FEJF Approach

• Plume Tophour (BEhour)2 (BEsize)2
  Ptopmax
• Plume Bottomhour (BEhour)2 (BEsize)2
  Pbotmax
• Layer1 Fractionhour 1 (BEhour BEsize)
• BEsize fire size-dependent buoyancy
  efficiency
• Behour hourly buoyancy efficiency
• Pbotmax maximum height of the plume bottom
• Ptopmax maximum height of the plume top
• BEsize, Ptopmax Pbotmax, and BEhour are provided
  in the FEJF Phase II fire report (Air Sciences,
  Inc., 2006).

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• SMOKE-Briggs Approach (SB)

• Plume Buoyancy Efficiency, F (m4/s3), as follows.
• F Q 0.00000258
• Q Heat Flux (btu/day),
• Buoyant Efficiency (BEsize)
• BEsize 0.0703 ln(acres) 0.03
• Smoldering Fraction (Sfract)
• Sfract 1 BE size
• NOTE possible bug in implementing smoldering
  fraction in SMOKE. We expect a larger fraction of
  emissions in layer 1 in SB.

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Heat Flux from FEPS

• Fire Emissions Productions Simulator (FEPS) was
  used to determine heat flux
• FEPS was developed by Anderson et al.
  http//www.fs.fed.us/pnw/fera/feps/
• User specifies the fire name, location, start
  date, end date, size, fuel type and other
  properties.
• FEPS calculates the hourly emissions and heat
  release.
• Uncertainty in specifying fire variables in FEPS
  might affect heat release estimate.
• Not available in batch mode so difficult to use
  FEPS in SB.

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Fire Events
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FEJF fire CharacteristicsOregon Prescribed Fire
PBOT Plume BottomPTOP Plume TopLAY1F
Emissions fraction in Layer 1
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FEJF fire CharacteristicsOregon Wild Fire
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Hourly Emissions per Layer Colorado Wild Fire
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Hourly Emissions Distribution Colorado Wild Fire
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Hourly Emissions per Layer Arizona Prescribed
Fire
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Hourly Emissions Distribution Arizona Prescribed
Fire
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Hourly Emissions per Layer Arizona Wild Fire
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Hourly Emissions Distribution Arizona Wild Fire
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Hourly Emissions per Layer Oregon Prescribed
Fire
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Hourly Emissions Distribution Oregon Prescribed
Fire
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Hourly Emissions per Layer Oregon Wild Fire
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Hourly Emissions Distribution Oregon Wild Fire
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Daily Emissions Fractions per Layer
CO FEJF 45 in surface layer, 45 above 2462
m. CO SB most emission between 200 - 1000 m.
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Results

• The FEJF approach places a large fraction of the
  emissions in the surface layer, and the plume
  with the remaining emissions are consistently
  located at higher layers compared to the SB
  approach.
• The plume bottom in FEJF depend on the fire size.
  It can be as high as several thousand meters
  above the first layer. In SB the plume bottom is
  always above the first layer.
• On daily basis, most of the emissions are in the
  first layer in FEJF, while in SB most of the
  emissions in the mid to upper layers.

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Conclusions

• The SB approach seems unrealistic since
  smoldering emissions should be located in the
  first layer.
• Since emissions occur during the day time when
  the boundary layer tends to be well mixed, model
  results might be insensitive to the vertical
  location of emissions within the boundary layer.
• To the extent that the FEJF approach locates
  emissions above the boundary layer, it might have
  smaller near field impact and greater long range
  transport.
• If fires occur at times when the boundary is
  shallow or poorly mixed, the FEJF approach might
  have a greater near field impact and less long
  range transport.

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Conclusions (2)

• Air quality modeling using CMAQ or CAMx is needed
  to determine of the two approaches would have
  significantly different air quality impacts,
  however, the current approach using FEPS is not
  feasible to model a large number of events.
• Because the differences in near field versus long
  range transport might depend on the meteorology
  conditions, it would be necessary to model a
  large variety of conditions to determine if the
  choice of FEPS or SB results in consistently
  different visibility impacts.
• SB approach would have greater near field impacts
  than FEJF if SMOKE is modified to locate a larger
  smoldering fraction in layer 1.