1. Holle | NWA Annual Meeting | October 06 Cloud Lightning from the National Lightning Detection Network (NLDN) Ronald L. Holle, Nicholas Demetriades, and Martin Murphy Vaisala, Inc. Tucson, Arizona

2. Holle | NWA Annual Meeting | October 06 -- Value of LF cloud data -- Overview of LF cloud data -- Spatial representation of lightning activity -- Validation of LF cloud performance Outline

3. Holle | NWA Annual Meeting | October 06 Low frequency (LF) cloud data in the NLDN Low frequency (LF) cloud lightning is typically located near cloud-to-ground (CG) lightning Cloud lightning precedes CGs in ~70% of all thunderstorms Cloud lightning typically precedes CGs by several minutes, but can precede CGs by > 60 minutes in some severe thunderstorms Cloud flash rates are typically 3 times larger than CG flash rates, but may be >10 times larger in some severe thunderstorms

4. Holle | NWA Annual Meeting | October 06 -- Value of LF cloud data -- Overview of LF cloud data -- Spatial representation of lightning activity -- Validation of LF cloud performance Outline

5. Holle | NWA Annual Meeting | October 06 Low frequency (LF) cloud lightning data in the National Lightning Detection Network (NLDN) Activated April 2006 to all users Detection methods are based on independent validation studies Weak positive cloud-to-ground (CG) flashes less than +15kA are now identified as cloud flashes, not as CGs 1/3 of the NLDN datastream is now LF cloud A network configured for optimal detection of CGs on a national level will not detect most LF cloud flashes

6. Holle | NWA Annual Meeting | October 06 The main challenge for LF cloud lightning detection: Source signal strengths The median LF large cloud pulse amplitude is 5% as strong as for CGs A network configured for optimal detection of CGs on a national level will not detect most LF cloud flashes CG Large cloud All cloud

7. Holle | NWA Annual Meeting | October 06 LF cloud data - NLDN The vertical component of the cloud flash is located with a median accuracy of 500 meters Cloud data are available in both the CG flash and CG stroke datastreams A fraction of all cloud flashes that occur can be detected by the NLDN - the detection efficiency (DE) is typically 5-15% with the standard sensor spacing of the NLDN LF cloud does not provide mapping of cloud lightning

8. Holle | NWA Annual Meeting | October 06 -- Value of LF cloud data -- Overview of LF cloud data -- Spatial representation of lightning activity -- Validation of LF cloud performance Outline

9. Holle | NWA Annual Meeting | October 06 LF cloud lightning detection data - Flash level Blue: Total VHF lightning mapping (1190 sources) Red: LF cloud lightning (5 sources) Dallas- Fort Worth region

10. Holle | NWA Annual Meeting | October 06 Green: NLDN CG flashes - Sources at storm level Red: NLDN-based test network LF cloud sources LF cloud flashes are typically located near the flash initiation point Dallas- Fort Worth region 18-minute period

11. Holle | NWA Annual Meeting | October 06 VHF total lightning mapping Areal coverage of flashes at the storm level Dallas- Fort Worth region 18-minute period

12. Holle | NWA Annual Meeting | October 06 -- Value of LF cloud data -- Overview of LF cloud data -- Spatial representation of lightning activity -- Validation of LF cloud performance Outline

13. Holle | NWA Annual Meeting | October 06 The main challenge for LF cloud lightning detection: Source signal strengths The median LF large cloud pulse amplitude is 5% as strong as for CGs A network configured for optimal detection of CGs on a national level will not detect most LF cloud flashes CG Large cloud All cloud

14. Holle | NWA Annual Meeting | October 06 LF cloud validation with LDAR II VHF mapping network Isolated storms, Dallas/Fort Worth, close NLDN spacing DE = detection efficiency Date Storm LDAR NLDN LF RelativeModeled flashes cloud DE (%)DE (%) 01 May 04 A 431 72 17%15-25% 01 May 04 B 91 35 3825-30 01 May 04 C 275 101 3725-30 13 May 04 39 9 2325-30

15. Holle | NWA Annual Meeting | October 06 The end Photo by James Gluba, Bloomington, IL