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

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University of North Carolina ... Air Sciences - Emissions Inventory ... Since emissions occur during the day time when the boundary layer tends to be ... – PowerPoint PPT presentation

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


1
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
2
Fire Plume Rise Modeling Project Status
  • Todays Presentation
  • Project Objectives
  • Plume Rise Modeling Methods
  • Fire Events Modeled
  • Results
  • Summary

3
Acknowledgments
  • Tom Moore and FEJF project design
  • Air Sciences - Emissions Inventory

4
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

5
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

6
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).

7
  • 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.

8
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.

9
Fire Events
10
FEJF fire CharacteristicsOregon Prescribed Fire
PBOT Plume BottomPTOP Plume TopLAY1F
Emissions fraction in Layer 1
11
FEJF fire CharacteristicsOregon Wild Fire
12
Hourly Emissions per Layer Colorado Wild Fire
13
Hourly Emissions Distribution Colorado Wild Fire
14
Hourly Emissions per Layer Arizona Prescribed
Fire
15
Hourly Emissions Distribution Arizona Prescribed
Fire
16
Hourly Emissions per Layer Arizona Wild Fire
17
Hourly Emissions Distribution Arizona Wild Fire
18
Hourly Emissions per Layer Oregon Prescribed
Fire
19
Hourly Emissions Distribution Oregon Prescribed
Fire
20
Hourly Emissions per Layer Oregon Wild Fire
21
Hourly Emissions Distribution Oregon Wild Fire
22
Daily Emissions Fractions per Layer
CO FEJF 45 in surface layer, 45 above 2462
m. CO SB most emission between 200 - 1000 m.
23
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.

24
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.

25
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.
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