1. Fire Plume Kinematic Structure Observed Using Doppler Wind Lidar
Allison Charland, Craig Clements, Daisuke Seto
Department of Meteorology and Climate Science
San José State University
San José, CA
American Meteorological Society
Ninth Symposium on Fire and Forest Meteorology
19 October 2011
San José State University
Fire Weather Research Laboratory

2. Overview Introduction Experimental Design Observations
Preliminary Results
San José State University
Fire Weather Research Laboratory

3. Introduction
A prescribed burn was conducted in complex terrain on 13 July 2011
The burn unit included ~660 total acres
Oak woodland
San José State University
Fire Weather Research Laboratory

4. Goals
To observe structure of the velocity field in the vicinity of a fire
Test the performance of the Doppler wind lidar for wildland fire applications
San José State University
Fire Weather Research Laboratory

5. Diablo Range Santa Cruz Mountains San Francisco Experimental Site
San Jose

6. Instrumentation 2 Remote Automated Weather Stations (RAWS)
T, RH, WS, WD, P
6.7-m In situ Tower
3D winds at 6.5 m
Turbulence
Sensible and Radiant Heat flux
2 Radiosonde Sounding Systems
GRAW GS-E
Vaisala, Inc., DigiCora MW31
Neal Waters Photography
San José State University
Fire Weather Research Laboratory

7. Instrumentation MiniSoDAR Doppler wind lidar Profiling Radiometer
Atmospheric Systems Corporation (ASC)
10 min, m AGL
Doppler wind lidar
Halo Photonics, Ltd. Stream Line 75
1.5 micron
Eye-safe
75 mm aperture all-sky optical scanner
Min Range: 80 m
Max Range: 10km
550 user defined range gates (24 m)
Temporal resolution: s
Profiling Radiometer
Radiometrics, Inc., MP-3000A
Neal Waters Photography
San José State University
Fire Weather Research Laboratory

8. Experimental Design Total of ~ 660 acres in the burn unit
Prevailing wind from the northwest
Ignited at the Northeast corner of the burn unit at 11:43 PST
Lidar placed upwind of burn area
Sodar placed downwind
Tower within the burn unit
RAWS near the lidar and the other higher on the ridge
Radiosondes launched at different times from along the ridge near the sodar and from near the lidar
Radiosonde
RAWS
Radiosonde

9. Lidar Scanning Techniques
Multiple elevation and azimuth angles were adjusted throughout the experiment to obtain the best scan through the fire plume.
Stare: Vertically pointing beam
Wind Profile
RHI (Range Height Indicator):
Fixed azimuth angle with varying elevation angles
PPI (Plan Position Indicator):
Fixed elevation angle with varying azimuth angles
30o
70o
95o
San José State University
Fire Weather Research Laboratory

10. Weather Conditions Background Soundings
Slight drizzle in the morning before the burn.
Morning soundings show a moist layer extending to 900 hPa drying out by noon.
Background Soundings
13 July PST
13 July PST
San José State University
Fire Weather Research Laboratory

11. Surface Conditions
Relative humidity between 50-70% during the time of the burn.
Wind speeds from 1-4 ms-1
With moisture in the morning and light wind speeds throughout the day, the fire intensity was fairly low for this particular burn.
San José State University
Fire Weather Research Laboratory

12. Tower Measurements
Increased heat flux to 4 kWm-2 as the fire passes the tower.
No signature in the vertical velocity as normally seen, due to lower intensity of the fire.
San José State University
Fire Weather Research Laboratory

13. Thermodynamic Plume Properties: Ridge Top Soundings
13 July PST
13 July PST
(gkg-1)
(gkg-1)
Warming near the surface through the fire plume ~4 K.
Enhanced moisture in the plume of 1 gkg-1.
San José State University
Fire Weather Research Laboratory

14. Kinematic Plume Properties: SoDAR
Time-height contours of vertical velocity and TKE
Downward motion shortly after ignition
Vertical motion above 100 m at 12:20
Increased turbulence within the plume
Ignition

15. Lidar: RHI Scans
Backscatter intensity and radial velocity vertical cross sections
7.5-45o elevation angle with increments of 2.5o and at a 95o azimuth angle for the time period of PST.
95o x z
1804 PST
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Fire Weather Research Laboratory

16. Lidar: RHI Scans Lidar was able to penetrate through the plume
Backscatter Intensity (dB)
Doppler Radial Velocity (ms-1)
1746 PST
1746 PST
Strong radial velocity underneath and within the plume
Weaker velocity aloft
1751 PST
1751 PST
Entrainment of the plume

17. Weaker radial velocity with dispersion
Lidar: RHI Scans
Backscatter Intensity (dB)
Doppler Radial Velocity (ms-1)
1759 PST
1759 PST
Weaker radial velocity with dispersion
of the plume
1805 PST
1805 PST

18. Lidar: PPI Scans 1755 PST
Maps at 30-70o azimuth angle with increments of 1.0o at a 10o elevation angle.
Lidar penetrates through the most intense part of the plume but is attenuated at times.
Increased velocity in the intense part of the plume.
Plume blocking the ambient wind.
San José State University
Fire Weather Research Laboratory

19. Summary
Moisture in the morning combined with low wind speeds throughout the day kept the fire intensity low for the prescribed burn.
LIDAR performed well, able to penetrate main convection core of the plume.
Increased turbulence within the plume.
Strong radial velocities beneath and within the plume.
Reduced velocities observed downwind of the plume indicating ambient wind modification.
San José State University
Fire Weather Research Laboratory

20. Future Work Further processing of Lidar data
Comparisons of Lidar measurements and in situ measurements
Collect Lidar data on more fires
San José State University
Fire Weather Research Laboratory

21. Acknowledgements CalFire Battalion Chief Dave McLean
NSF Grant #
USDA #07-JV
Neal Waters Photography
San José State University
Fire Weather Research Laboratory