Lightning The LDAR II Network Nicholas W. S. Demetriades, Ronald L. Holle and Martin J. Murphy Vaisala, Inc., Tucson, Arizona HEAT Project - First Planning Workshop Boulder, CO March 2004

Presentation Outline - 1 Brief description of the NLDN Description of LDAR II Mapping lightning flashes in 3 dimensions Spatial extent of LDAR II, NLDN and radar reflectivity data Total lightning uses for thunderstorm growth, decay and organization

Presentation Outline - 2 LDAR II source density images (an alternative way of representing the data) 3-dimensional lightning structure in MCSs LDAR II flash initiation points for cell tracking Conclusions

NALDN - CG Flash Detection Efficiency

24-hour NALDN Map

LDAR II - What Does it Detect? LDAR II detects pulses of radiation produced by the electrical breakdown processes of lightning in a 5 MHz band within a subset of the VHF ( MHz) band VHF pulses of radiation can then be used to reconstruct the path (map) of CG and Cloud lightning discharges in 2D or 3D

3D/2D Lightning Mapping - LDAR II 3-Dimensional Mapping within Network Perimeter meter location accuracy Greater than 95% expected flash detection efficiency Reduces to 2-Dimensional Mapping well outside of the Network (~150 km) 2 km or better location accuracy Greater than 90% expected flash detection efficiency out to 120 km

LDAR II sensor: DFW Airport

Dallas-Fort Worth LDAR II Network

3D Cloud Discharge Mapping A Bi-level Cloud Flash detected by the DFW LDAR II Network on 11 April 2001 Initial upward breakdown, followed by charge re- organization on both the upper positive and lower negative charge regions Upper positive charge region is shown by higher density sources between 7 and 10 km and lower negative charge layer is shown by lower density sources between 4 and 6 km Initial Upward Breakdown

Spider Lightning Flash Detected by the DFW LDAR II Network 13 October 2001 Produced 2 Isolated CG Discharges (White Lightning Symbols) along its Total Path Length of ~190 km

DFW LDAR II Sources (red) and NLDN CG Flashes (black) detected between UTC 13 October 2001 Fort Worth WSR-88D Radar Base Reflectivity Image 13 October 2001 at 0105 UTC Area covered by WSR-88D Reflectivity, LDAR II Total Lightning and CG Lightning

MCS Lightning as shown by LDAR II and the NLDN LDAR II Sources (Red) and NLDN Flashes (Black) detected between 0312:30 and 0317:30 UTC 15 June 2001 Fort Worth WSR-88D Base Reflectivity Image from 0315 UTC 15 June 2001

Thunderstorm Growth and Decay: Cloud Lightning Flash Rates

Total lightning sources detected by the DFW LDAR II Network within an isolated thunderstorm between 0345 and 0615 UTC 25 May 2002 White arrow identifies height rise during thunderstorm growth phase and the purple arrows identify height descent during thunderstorm decay phase Thunderstorm Growth and Decay: LDAR II Altitude Information

Thunderstorm Organization: Total and Horizontally Extensive Lightning Flash Rates

LDAR II Source Density Images: Lightning Holes - Lightning Holes (white arrows) detected in two supercell storms between 0304 and 0307 UTC 6 April These storms were producing baseball to grapefruit sized hail at this time - Lightning Holes are caused by very strong updrafts - Very strong updrafts are not easily identified with radar reflectivity

LDAR II Source Density Images: Lightning Notches - Lightning Notch (white arrow) detected in a supercell storm between 0030 and 0032 UTC 11 October Lightning Notches are probably caused by either strong rear inflow or a highly sheared lightning hole - These signatures have only appeared in severe storms

UTC UTC UTC LDAR II Source Density Images: Bow Echo Evolution 13 October 2001

3-dimensional MCS Lightning Structure LDAR II Sources detected between 0205 and 0207 UTC 13 October 2001 Fort Worth WSR-88D Base Reflectivity Image from 0204 UTC 13 October 2001

3-dimensional MCS Lightning Structure: Radar reflectivity and lightning source density

DFW LDAR II sources (red) and flash initiation points (black) detected between 0110 and 0112 UTC 13 October 2001 DFW LDAR II sources detected between 0110 and 0112 UTC 13 October 2001 Flash Initiation Points for Cell Identification

Conclusions The Houston, TX LDAR II network will give a complete representation of total (cloud plus CG) lightning activity in and around the Houston area Lightning flash initiation points will help identify important cloud microphysical and kinematic relationships for lightning generation The structure of lightning flashes in 3 dimensions will help identify important cloud microphysical and kinematic relationships for lightning propagation in thunderstorms