1. A Summary of the NASA Lightning Nitrogen Oxides Model (LNOM) And Recent Results 10 th Annual CMAS Conference, Chapel Hill, NC October 24-26, 2011 William Koshak* Earth Science Office, NASA Marshall Space Flight Center, Huntsville, AL, USA Harold Peterson National Space Science & Technology Center, Huntsville, AL, USA Acknowledgements: This work supported under ROSES NRA NNH08ZDA001N (A.18 Decisions; PI Arastoo Biazar of the University of Alabama in Huntsville), ROSES NRA NNH09ZDA001N-ACMA (A.15 Atmospheric Composition Modeling and Analysis; PI Yuhang Wang of the Georgia Institute of Technology), and the NASA Post-doctoral Program (NPP).

3. Recent LNOM Upgrades  Channel Length Computation Upgrade  Negative Charge Layer (“N-region”) Height Upgrade  Leader Current Value Upgrades  Flash-Typing Upgrade  Continuing Current Upgrades

4. Channel Length Computation Upgrade o Spatial averaging of VHF sources changed from (1 km) 3 to (100 m) 3 o Better accounts for channel tortuosity  increases channel length estimates o Other changes in LNOM affect channel length as well, but to lesser degree Aug 2006 Ave Length = 10.7 km Aug 2006 Ave Length = 51.4 km OLD NEW

5. N-Region Height Upgrade o Using lower max in SAD involves manual labor, is slow, & can be inaccurate o Using -15C isotherm height (where charging occurs) is automatic/quick & accurate Mean sea-level temp for the month analyzed is found + use assumed atmo lapse rate OLD NEW + + + + + + + + -- - - -- - - - ---- - - -15C Segment Altitude Distribution (SAD)

6. Leader Current Value Upgrades o More recent literature suggests better values Leader TypeOLDNEW Stepped Leader (Ground Flash) 100A1.3kA Dart Leader (Ground Flash) 1kA1.7kA Hot Core Leader (Cloud Flash) 100A130A

7. Flash-Typing Upgrade o According to Cummins & Murphy (2009), NLDN-detected flashes with positive peak currents between 10-20kA are in reality a mixture of ground and cloud flashes so the flash-type is ambiguous. o So LNOM no longer attempts to force a know type (ground or cloud) for such a flash, but instead the flash is removed from any LNOM analysis … “when in doubt throw out”.

8. Continuing Current Upgrades o Old parameterization: employed complicated “wave propagation model” to estimate CC duration, but duration probably doesn’t decrease when approaching the ground New parameterization: simply employs a 100 ms duration all along the RS channel. o Also: 75% of +CGs now get CC, whereas 30% of –CGs get CC. (Previously, 30% of all CGs got CC.) OLD NEW

12. TypeVariable2005200620072005-2007 GROUND FLASHES Number 59355254414115330 Average NOx per ground flash (moles) 696.7581.9526.4611.3 CLOUD FLASHES Number 457743543428526109734 Average NOx per cloud flash (moles) 55.755.047.153.2 ALL FLASHES Number 517094068832667125064 Average NOx per flash (moles) 129.2123.1107.9121.6 Summary Statistics for Lightning NOx

13. Thank You!