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A Summary of the NASA Lightning Nitrogen Oxides Model (LNOM) And Recent Results

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

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A Summary of the NASA Lightning Nitrogen Oxides Model (LNOM) And Recent Results

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  1. A Summary of the NASA Lightning Nitrogen Oxides Model (LNOM) And Recent Results 10th 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).

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

  3. Channel Length Computation Upgrade • Spatial averaging of VHF sources changed from (1 km)3 to (100 m)3 • Better accounts for channel tortuosity  increases channel length estimates • 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

  4. N-Region Height Upgrade • Using lower max in SAD involves manual labor, is slow, & can be inaccurate • 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 Segment Altitude Distribution (SAD) + + + + + + + + -15C • - - - -- - • - ---- - - OLD NEW

  5. Leader Current Value Upgrades • More recent literature suggests better values

  6. Flash-Typing Upgrade • 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. • 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” .

  7. Continuing Current Upgrades • 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. • Also: 75% of +CGs now get CC, whereas 30% of –CGs get CC. • (Previously, 30% of all CGs got CC.) NEW OLD

  8. Summary Statistics for Lightning NOx

  9. Thank You!

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