# Presentation: 673867

## OMI Tropospheric NO2 from Lightning in Observed Convective Events

**Ken Pickering – NASA Goddard**
**Eric Bucsela – UMBC/GEST, NASA/GSFC**
**Tom Kucsera – UMBC/GEST, NASA/GSFC**
**Laura Pan - NCAR**
**Chris Davis - NCAR**
**James Gleason – NASA Goddard**
**Pieternel Levelt - KNMI**

## Introduction

**Lightning produces ~15% of total NOx emissions.**
**Most likely global LNOx production is 2 – 8 TgN/yr (Schumann and Huntrieser, 2007, *****ACP*****).**
**Most of lightning-produced NOx injected into middle and upper troposphere; important for UT ozone production, especially in tropics.**
**Previous satellite lightning NO2 (LNO2) analyses:  Events:  Richter and Burrows (2002); Thomas et al. (2003); Beirle et al. (2004; 2006)**
**	****Global:  Boersma et al. (2005), Martin et al. (2007)**
**This analysis uses OMI tropospheric NO2 to obtain estimates of LNOx production in specific convective events over the Central USA.**

## Procedure

**Cases of possible NO2 from lightning (LNO2) downstream of observed storms identified from NASA standard retrieval tropospheric NO2 data sets**
**OMI data screened for 100% cloud cover for days of interest**
**NO2 profile shapes from cloud-resolved modeling of midlatitude storms with lightning used in estimating appropriate AMFs**
**Background (pollution, soil NOx, lightning from other storms) is removed by subtracting monthly mean**
**	****LNO2 = (OMINO2****trop ****– OMINO2****tropMonthlyMean****) x (AMF****GEOS-Chem**** / AMF****lightning****)**
**Estimate LNOx by assuming that LNO2 is 30% of LNOx in 500 – 200 hPa layer.**

## Procedure (continued)

**Run set of back trajectories starting at 500, 300, and 200 hPa with 1 x 1 degree separation from region of enhanced OMI NO2 from time of OMI overpass, and count  upstream NLDN CG flashes in 1 x 1 degree grid boxes.  Assume decay rate equivalent to 3.5-day NOx lifetime in UT.**
**Obtain vertically weighted average number of upstream CG flashes using vertical profile of LNOx from prior cloud-resolved model simulations.**
**Adjust CG flash counts for NLDN detection efficiency of ~90%.**
**Scale up the CG flash counts to total flashes using the Boccippio et al. (2001) IC/CG ratio climatology.**
**Divide estimates of moles of LNOx in enhanced region by number of total upstream flashes to obtain average moles/flash**

## LNO2 profile from UMD

**Cloud Chemistry Model**
**averaged over simulations**
**for three midlatitude storms**
**Profile representative of**
**outflow 100 km downwind**
**of storm core**

**With 40% cloud cover:**
**AMF with GEOS-Chem**
**   ****NO2 profile ~ 0.9**
**AMF with anvil outflow**
**   ****NO2 profile ~ 2.0**

## Case 1:  June 3, 2005

**Case 1:  June 3, 2005**

**Cloud Cover**

**Level 2 OMI Tropospheric NO2**

**After removal of pixels with 100% cloud cover**

**LNO2 on 0.25 x 0.25 degree grid**

**1.64 +/- 0.617 x 10****6**** moles NO2**

**2.35 +/- 0.618 x 10****6**** moles NO2**

## Case 1:  June 3, 2005

**Case 1:  June 3, 2005**

**0000-0100 UT**

**0600-0700 UT**

**1200-1300 UT**

**1800-1900 UT**

## Slide 8

## Case 1:  Calculations

**Upstream CG Flashes:****	****	****Using LNOx mass profile from**
**500 hPa****	****	****1724****	****	****midlatitude cloud-resolved simulations:**
**300****	****	****3031**
**200****	****	****1750****	****	****Vertically mass-weighted ****	****	****	****	****	****upstream CG flashes = 2163**

**Boccippio et al., 2001**

**Scaling up to total flashes**
**using detection efficiency of**
**90% and mean IC/CG ratio = 6**
**for region of upstream flashes**
**yields ****16,827 flashes**

## Case 1:  Calculations

**Scaling up to NOx from NO2:**
**2.35 x 10****6**** moles NO2 x 1 mole NOx/0.3 moles NO2**
**	****= 5.47 x 10****6**** moles NOx**
**Estimating average moles NOx per flash:**
**7.83 x 10****6**** moles NOx / 16827 flashes**
**	****= ****465 +/- 122 moles NOx/flash**

**Effective Cloud Fraction **

**Large source of uncertainty**

## Case 2:  June 22, 2006 - Oklahoma

**Case 2:  June 22, 2006 - Oklahoma**

**Cloud Cover**

**Level 2 OMI Tropospheric NO2**

**After removal of pixels with 100% cloud cover**

**LNO2 on 0.25 x 0.25 degree grid**

**1.91 +/- 0.522 x 10****6**** moles NO2**

**1.33 +/- 0.519 x 10****6**** moles NO2**

## Slide 12

## Case 2:  Calculations

**Upstream CG flashes:**
**500 hPa****	****	****540**
**300****	****	****	****794**
**200****	****	****	****1610**

**Vertical mass weighting and detection efficiency**
**correction yields 868 CG flashes**

**Scaling up to total flashes using mean **
**IC/CG ratio of 4 for upstream region**
**yields 4339 total flashes**

**Scaling from NO2 to NOx:**
**1.33 x 10****6**** x 1 mole NOx/0.3 moles NO2**
**	****= 4.43 x 10****6**** moles NOx**
**Estimating moles LNOx per flash:**
**4.43 x 10****6**** moles NOx/4339 flashes =**
**	****997 +/- 389 moles NOx/flash**

**Cloud Cover**

##  Case 3:  June 22, 2006 Missouri

**       ****LNO2 on 0.25 x 0.25 degree grid****	**** ****	****                Effective Cloud Fraction**

** ****	****       ****AMF****GEOSChem****	**** ****	****	****                                 AMF****lightning**

**2.47 +/- 0.653 x 10****6**** moles NO2**

## Slide 15

## Case 3:  Calculations

**Upstream CG flashes:**
**500 hPa****	****	****1824**
**300****	****	****	****2145**
**200****	****	****	****3473**

**Vertical mass weighting and detection efficiency**
**correction yields 2413 CG flashes**

**Scaling up from CG to total flashes using**
**mean IC/CG ratio of 4 for upstream region**
**yields 12,066 flashes**
**Scaling up from NO2 to NOx:**
**2.47 x 10****6**** x 1 mole NOx/0.3 moles NO2**
**	****= 8.23 x 10****6**** moles NOx**
**Estimating average moles per flash:**
**8.23 x 10****6**** moles NOx/12066 flashes**
**	****= ****682 +/- 180 moles NOx/flash**

**Average over 3 cases:**
**715 +/- 215 moles NOx/flash**

## *

**Lightning NO Production Scenarios**

**Summary of Five Simulated Storms**

**Means:  500 moles/flash**
**               ****0.94 ratio**

- Orville et al., 2002

*****

**OMI:  3 US storms**

## Summary

**Cases of LNOx detected in OMI tropospheric NO2 data over Central U. S.**
**Employed AMFs appropriate for convective outflow regimes containing LNOx.  These AMFs are approximately a factor of 2 larger than those from GEOS-Chem used in the standard retrieval.**
**Estimates of LNOx production for 3 cases range from 465 to 997 moles/flash (mean = 715 moles/flash with 25-40% OMI retrieval uncertainty).  This is at the high end of other recent continental US estimates.**
**Main uncertainties:  radiative transfer in substantial cloud cover, magnitude of tropospheric background NO2 column, IC/CG ratio.**
**OMI-based estimates, cloud-resolved modeling, and GEOS-Chem simulations all suggest NO production/flash in US > global mean**

## Future

**Refine LNOx production estimates for these three cases:**
**	****	****Oklahoma case – likely can obtain actual IC/CG ratio ****	****	****from 3-D Lightning Mapping Array data**
**	****	****Run trajectories with higher-resolution data from WRF**
**Conduct similar analyses with OMI data for Northern Australia and Costa Rica regions:**
**	****	****Aircraft data available from SCOUT-O3/ACTIVE and ****	****	****NASA TC4 field experiments**
**	****	****Cloud-resolved modeling for specific events from**
**	****	****	****these experiments is underway or will be**
**	****	****	****conducted in the near future **
**	****	****Do tropical lightning flashes make less NOx per flash**
**	****	****	****than midlatitude flashes?**