Dye slides

On the extension of lightning into anvils of Florida thunderstorms : 

On the extension of lightning into anvils of Florida thunderstorms James E. Dye National Center for Atmospheric Research Boulder Colorado Presentation for LIS International Workshop Huntsville Alabama Sept. 10 – 13, 2006

AIRBORNE FIELD MILL PROJECT II : 

AIRBORNE FIELD MILL PROJECT II Primary Goals: Investigate electric fields in relationship to microphysics and reflectivity in anvil and debris clouds. Investigate the decay of electric field in anvils. Use the findings to help develop new Lightning Launch Commit Criteria rules for launch of space vehicles. Conducted near Kennedy Space Center June 2000 & 2001. In-situ electric field and microphysics observations in anvils and other clouds with the U. of No. Dakota Citation. Coordinated with PAFB 5 cm radar and Melborne NEXRAD. Lightning detection with LDAR and CGLSS systems at KSC. Many participants from many organizations.

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J.E. Dye, M.G. Bateman, H.J. Christian, E. Defer, C.A. Grainger, W.D. Hall, E.P. Krider, S.A. Lewis, D.M. Mach, F.J. Merceret, J.C. Willett, P.T. Willis With Thanks to my many co-authors Submitted to J. of Geophysical Research May 23, 2006 The ABFM project was funded primarily by NASA Kennedy Space Center with a significant contribution from the U.S. National Reconnaissance Office. NCAR is sponsored by the National Science Foundation. Electric Field, Cloud Microphysics, and Reflectivity in Anvils of Florida Thunderstorms [ An overview of results from the Airborne Field Mill Project II ]

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CAPPIs at 4, 7 & 10 km msl with a 9 min segment of A/C track overlaid. Red triangles = CG flashes + = VHF sources from LDAR 4 km 7 km 10 km Flight level Start of A/C track

Slide5: 

MER Plot 2100 to 2100 (Microphysics, Electric Field, and Reflectivity) Particle Concentrations (# per liter) Electric Field (kV/m) Total Field == bold line Vertical E == light line Note: The abrupt increase of electric field at ~10 dBZ, but particle concentrations increase smoothly. Reflectivity curtain along A/C track. Total 2D Conc. 2D >1mm

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Number Distributions Area Distributions FSSP 2D-C, 1D-C HVPS Estimated time to decay from 50 to ~ 0 kV/m from John Willett’s anvil model

Slide7: 

30 sec averages; Black – points with E >10 kV/m Results from 14 flights in 29 different anvils

Avg. Reflectivity in Cube of 3 km  centered on A/C position: 

Avg. Reflectivity in Cube of 3 km centered on A/C position Particles > 1mm Particles > 3mm Particles 100-200 µm Particles 0.2 – 1 mm vs. Particle Concentrations at different sizes

Slide9: 

Total Electric Field (kV/m) Total Electric Field (kV/m) Electric Field as a function of Particle Concentration for ALL anvil cases observed in ABFM 30 sec averages (~3 km distance); 14 cases; 2189 total points Includes measurements near convective cores and lightning Total Concentration from 2DC Concent. of Particles > 1 mm from 2DC

Slide10: 

Electric Field Strength vs. Average Reflectivity in 3 km Cube centered on A/C position

Slide11: 

10 sec averages (~1 km distance); from 14 anvil cases. EXCLUDES measurements near convective cores and lightning Possible Reflectivity Parameters for New LLCC Anvil Rule Reflectivity Averages of 11x11 km Columns Volume Avg. Height Integrated Radar Reflect. = (11 x11 km dBZ Avg) X (Avg. Anvil Thick.) No Hazard ZONE No Hazard ZONE Total Electric Field (kV/m) Total Electric Field (kV/m) No Hazard Zone VAHIRR

Slide12: 

~7 min of A/C track

Slide13: 

LDAR Central Sensor

Slide15: 

LDAR Central Sensor

Slide20: 

from STEPS in Kansas/Colorado June 29,2000 tornado case

from STEPS in Kansas/Colorado June 29,2000 tornado case: 

from STEPS in Kansas/Colorado June 29,2000 tornado case

from STEPS in Kansas/Colorado June 29,2000 tornado case: 

from STEPS in Kansas/Colorado June 29,2000 tornado case

Concluding Remarks: 

Concluding Remarks ABFM results of measurements in anvils show that E fields are < 3 kV/m when average reflectivity is <5 dBZ (No possibility of triggering lightning.) Some evidence from ABFM for Natural Lightning not extending into anvil regions with reflectivity <15 – 20 dBZ. This statement does not apply near storm cores. Needs to be examined more carefully and in different geographical regions.

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