Fire P lume K inematic S tructure O bserved U sing Doppler W ind L idar

1. Fire Weather Research Laboratory San José State University 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

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

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

4. Fire Weather Research Laboratory San José State University 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

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

6. Fire Weather Research Laboratory San José State University 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

7. Fire Weather Research Laboratory San José State University Instrumentation • MiniSoDAR • Atmospheric Systems Corporation (ASC) • 10 min, 20-200 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: 0.1-30 s • Profiling Radiometer • Radiometrics, Inc., MP-3000A Neal Waters Photography

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. Fire Weather Research Laboratory San José State University Lidar Scanning Techniques 30o • 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 70o 95o

10. Fire Weather Research Laboratory San José State University Weather Conditions • 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 2011 0900 PST 13 July 2011 1149 PST

11. Fire Weather Research Laboratory San José State University 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.

12. Tower Measurements Fire Weather Research Laboratory San José State University • 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.

13. Thermodynamic Plume Properties: Ridge Top Soundings Fire Weather Research Laboratory San José State University 13 July 2011 1237 PST 13 July 2011 1644 PST (gkg-1) (gkg-1) • Warming near the surface through the fire plume ~4 K. • Enhanced moisture in the plume of 1 gkg-1.

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 Fire Weather Research Laboratory San José State University • 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 1701-1830 PST. 95o z x 1804 PST

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

18. Lidar: PPI Scans 1755 PST Fire Weather Research Laboratory San José State University 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.

19. Fire Weather Research Laboratory San José State University 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.

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

21. Fire Weather Research Laboratory San José State University Acknowledgements • CalFire • Battalion Chief Dave McLean • NSF Grant #0960300 • USDA #07-JV-11242300-073 Neal Waters Photography