application of a portable doppler wind lidar for wildfire plume measurements allison charland and...
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Application of a Portable Doppler Wind Lidar Application of a Portable Doppler Wind Lidar for Wildfire Plume Measurementsfor Wildfire Plume Measurements
Allison Charland and Craig ClementsDepartment of Meteorology and Climate Science
San José State UniversitySan José, CA
American Meteorological Society16th Symposium on Meteorological Observation and Instrumentation
25 January 2012
San José State UniversityFire Weather Research Laboratory
Introduction
• Doppler wind lidar deployed on a prescribed burn was conducted in complex terrain on 13 July 2011
San José State UniversityFire Weather Research Laboratory
Goals
• To observe structure of the velocity field in the vicinity of a wildland fire
• To test the performance of the Doppler wind lidar for wildland fire applications:
- Determine the plume boundaries- Estimate fire spread rate- Identify maximum height of the plume
San José State UniversityFire Weather Research Laboratory
CSU-MAPS InstrumentationCalifornia State University-Mobile Atmospheric Profiling System
•Portable 32-m Micromet Tower•Vaisala, Inc. Digicora MW31 radiosonde sounding system•Radiometrics, Inc., MP-3000A profiling radiometer•Halo Photonics, Ltd. Stream Line 75 Doppler Wind Lidar
San José State UniversityFire Weather Research Laboratory
Instrumentation
• 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: 0.1-30 s•Measurements:
• Backscatter Intensity • Doppler Radial Velocity
San José State UniversityFire Weather Research Laboratory
Experimental Site
San Jose
San Francisco
Diablo RangeSanta Cruz M
ountains
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
RAWS
Weather Conditions• Slight drizzle in the morning before the burn.• Wind speeds from surface stations of 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.
-10 -5 0 5 10 15
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950
Temperature (oC)
Pre
ssur
e (h
Pa)
-15 -10 -5 0 5 10 15 20
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950
Temperature (oC)
Pre
ssur
e (h
Pa)
13 July 2011 0900 PST 13 July 2011 1149 PST
Background Soundings
San José State UniversityFire Weather Research Laboratory
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
San José State UniversityFire Weather Research Laboratory
95o
30o
70o
San José State UniversityFire Weather Research Laboratory
Lidar Processing Techniques
500 1000 1500 2000 2500 3000 3500-10
0
10Radial velocity Component (ms-1)
500 1000 1500 2000 2500 3000 3500-10
0
10Radial velocity Component (ms-1)--After Filter
500 1000 1500 2000 2500 3000 3500
1
1.5
2Backscatter Intensity
500 1000 1500 2000 2500 3000 3500
1
1.5
2
Range Gate
Backscatter Intensity--After Filter
Lidar: PPI ScansMaps 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.
San José State UniversityFire Weather Research Laboratory
30o
70o
San José State UniversityFire Weather Research Laboratory
Finding Plume Edge Boundaries• An algorithm for determining plume
edge boundaries was implemented following Kovalev et al. 2005
• The plume edge boundary can be determined by the location of the maximum of
• Similar algorithm was applied to determine the edge behind the plume.
0 5 10 15 20 25 30 35 40 45 501
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Range Gate
B
0 5 10 15 20 25 30 35 40 45 500
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4
6x 10
-3
Range Gate
D
Front
End
Velocity Field Around PlumeBackscatter Intensity Doppler Radial Velocity (ms-1)
1750 PST 1750 PST
1752 PST1752 PST
Velocity Field Around PlumeBackscatter Intensity Doppler Radial Velocity (ms-1)
1755 PST 1755 PST
1757 PST1757 PST
Estimated fire spread rate
Two methods were used to determine average spread rate of the plume derived from 90 minutes of scans.
San José State UniversityFire Weather Research Laboratory
2.4 ms-1
0.67 ms-1
Convection Core Tracking
Plume Tracking
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.
95o
San José State UniversityFire Weather Research Laboratory
1804 PST
x
z
Estimating Plume HeightBackscatter Intensity
1830 PST
1746 PST
• For each range gate, the ratio F as a function of elevation angle ø can be computed by:
• By finding the maximum value of F throughout the scan, the maximum height of the plume can be found.
Estimating Plume HeightBackscatter Intensity
1830 PST
1746 PST
Doppler Radial Velocity (ms-1)
1746 PST
1830 PST
Summary•Scanning Doppler lidar performed well, able to penetrate main convection core of the plume.•Determination of the plume boundaries allowed for easier analysis of the velocity field around the plume.•Reduced velocities observed downwind of the plume indicating ambient wind modification.•Convection-core tracking may be a useful surrogate for estimating fire spread rate.•Algorithm was able to identify the maximum height of the plume.•Strong radial velocities beneath and within the plume.
San José State UniversityFire Weather Research Laboratory
Future Work
•Develop faster scanning strategies.•Lidar will be truck-mounted for an experiment in May.•Test Lidar performance on more intense fires.
San José State UniversityFire Weather Research Laboratory
Acknowledgements
• CalFire– Battalion Chief Dave McLean
• NSF Grant #0960300
• USDA #07-JV-11242300-073
San José State UniversityFire Weather Research Laboratory
Neal Waters Photography