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M a t u s M a r t i n i Dale Allen, Kenneth Pickering, Amanda Hansen, Barry Baker

Impact of lightning-NO and radiatively -interactive ozone on air quality over CONUS, and their relative importance in WRF- Chem. M a t u s M a r t i n i Dale Allen, Kenneth Pickering, Amanda Hansen, Barry Baker. Atmospheric and Oceanic Science

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M a t u s M a r t i n i Dale Allen, Kenneth Pickering, Amanda Hansen, Barry Baker

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  1. Impact of lightning-NO and radiatively-interactive ozone on air quality over CONUS, and their relative importance in WRF-Chem Matus M artini Dale Allen, Kenneth Pickering, Amanda Hansen, Barry Baker Atmospheric and Oceanic Science University of Maryland, College Park, MD WRF Users’ Workshop, Boulder, CO June 28,2012

  2. Why is lightning NOx important Indirectly affects our local air quality and global climate NOx = NO + NO2 • primary pollutant found in photochemical smog • precursor for tropospheric O3 formation O3 • is the third most important greenhouse gas • impacts the Earth’s radiation budget • (can cause changes in atmospheric circulation patterns) • is toxic to humans, plants and animals

  3. Recently EPA has proposed tighteningthe air quality standard even further, current NAAQS for ozone is 75 ppbv. What is the lightning contribution to policy relevant background ozone? Increase in 8-hr O3 due to LNOx Impact of lightning-NO on Colorado air quality is large (sunny conditions, good mixing). Mean contribution of LNOx to surface layer ozone during July 2007 was 9 ppbvas diagnosed by WRF-Chem. 8-hr ozone [ppbv] at surface

  4. New approaches • WRF-Chem simulations are driven by NASA’s MERRA reanalysis. • Initial and boundary conditions for chemical species are taken from NASA’s global chemical transport model GMI with combined stratospheric and tropospheric chemistry (two separate GMI simulations, also driven by MERRA, with and without lightning-NO emissions). • The most recent segment altitude distributions of VHF sources from the Northern Alabama Lightning Mapping Array to best represent the vertical distribution of lightning-NO (with “N-region” peak at height of -15°C isotherm which averages 7.3 km AGL for the eastern U.S. and 5.5 km AGL for mountains). • A look up table that utilizes convective precipitation and mixed phase depth (indicative of lapse rate) to estimate total flash rates over the CONUS. • Interactive ozone in longwave and shortwave radiation schemes.

  5. Assumed O3 profiles in longwave and shortwave schemes Goddard SW: 5 profiles(tropical, midlatitude summer/winter, polar summer/winter) RRTM schemes: 1 profile prescribed CAM schemes: 12 monthly profiles Longwave scheme (RRTM) uses the average of midlatitude summer and midlatitude winter profiles (WRF default RRTM). Shortwave scheme (Goddard) uses midlatitude summer for latitudes 30–60°N andtropicalO3profile south of 30°N.

  6. Assumed O3 profiles in radiation schemesvs. WRF-Chem calculated profiles O3 generated from LNOx emissions (blue shaded area) Enhancement of 22 ppbv between 5–12 km Longwave scheme (RRTM) uses the average of midlatitude summer and midlatitude winter profiles (WRF default RRTM). Shortwave scheme (Goddard) uses midlatitude summer for latitudes 30–60°N andtropicalO3profile south of 30°N.

  7. Single column experiments with offlineRRTM longwave scheme for clear-sky conditions Integrated LW Ozone band Midlatitudesummer profile Tropical profile

  8. Single column experiments with offlineRRTM longwave scheme for clear-sky conditions Midlatitude summer profile Tropical profile

  9. Single column experiments with offlineRRTM longwave scheme for clear-sky conditions Midlatitude summer profile Tropical profile Vertical sensitivity of heating rate due to changes in vertical ozone distribution. Adding ozone at an atmospheric layer causes an increase of the heating rate at that level. 40-ppbv ozone increments were added to each atmospheric layer. The peak increases of heating rate are normalized to 1 Dobson unit ozone increment. The most sensitive is the upper troposphere at ~12 km (20% increase if 1 DU ozone added).

  10. WRF-Chemtests Version 3.2.1 Ten 4-day simulations, reinitialized every 3rd day for July 2007 36 km horizontal resolution, 40 vertical levels up to 50 hPa Four sensitivity simulations: • Standard (no LNOx) • With LNOx • No LNOx, interactive ozone • With LNOx, interactive ozone Interactive ozone simulations pass ozone from the chemistry array to both the longwave and shortwave radiation schemes at each radiation time-step. Non-interactive ozone uses one prescribed ozone profile for each grid point. No data assimilation Ten cases = one month

  11. WRF-Chem configuration

  12. Impact of different meteorological IC/BC(July 8, 2007 snapshots) Stage IV NCEP WRFNARRWRFMERRA T = 54 hour T = 42 hour 6 hour Accum [mm] Precipitation: 6 hour accumulation [mm]

  13. Time series of daily flash rate over CONUS Flash rate based on Hansen et al. [2011] look up table Look-up table (Hansen et al. 2011) that uses mixed phase depth (measure of lapse rate) and convective precipitation is prone to model biases (precipitation and temperature) and vertical resolution. Advantage: no need to scale the modeled flash rate to observed. We use combination of look-up table and scaling – slightly better day-to-day variation (correlation of 0.51 vs. 0.49) compared to approach of Allen and Pickering [2002]. Overestimation with respect to OMI NO2colums (DOMINO). IC/CG ratio likely overestimated.

  14. Ozone enhancements from LNOx(Difference between two simulationswith LNOx and without LNOx emissions) WRF-Chem GMI CTM –> WRF-Chem Pressure [hPa] O3 [ppbv] at 300 hPa 2° x 2.5° –> 36 km Both driven by MERRA reanalysis.

  15. Impact of interactive ozone on OLR (Difference between interactive O3 simulation and climatological O3 simulation) No LNOx LNOx Need to compare to observed OLR. Fast et al. [2006] showed that simulated SW radiation was 30–40 Wm-2 closer to observations when aerosols were coupled, a factor of 10 smaller effect of ozone.

  16. Outgoing longwave radiation due to LNOx(Difference between two simulations with LNOx and without LNOx emissions) Ozone generated from LNOxreduces the OLR by 0.22 Wm-2during the month of July 2007 on average, 0.43 Wm-2 for clear sky in a fully coupled framework. Martini et al. [2011] showed values of 0.20–0.50 Wm-2 for summer 2004 in offline calculations for clearsky.

  17. Impact of interactive ozone(Difference between interactive O3 simulation and climatological O3simulation) Temperature at 200 hPa Ozone at 200 hPa We see temperatures cooler by 0.1°C, because there is much less modeled O3 (tropopause at higher altitude) than assumed climatology in longwave scheme.

  18. Ozone Temperature Temp Bias Observations with s bars When LNOx emissions are in place interactive O3improves temperatures above 200 hPa.

  19. Ozone Temperature Temp Bias Observations with s bars When LNOx emissions are in place interactive O3 has improves temperature above 200 and below 600 hPa.

  20. Summary • The heating rates are most sensitive the upper troposphere around 12 km, with no impact below 5 km. • Back of envelope calculation: Impact on O3 can be 1 ppbv. Climate penalty factor ~2.2 ppbv/K [Bloomer et al. 2009] and temperature response, determined from climate simulations, of 0.3 K per 18-ppbv O3 enhancement [Mickley et al. 2004]. • Impact of using modeled O3 in LW scheme on OLR: 3.2 Wm-2on average with 4.0 Wm-2 for clear sky. Fast et al. [2006] showed that simulated SW radiation was 30–40 Wm-2 closer to observations when aerosols were coupled, a factor of 10 smaller effect of ozone. • Ozone generated from LNOxreduces the OLR by 0.22 Wm-2on average, 0.43 Wm-2 for clear sky in a fully coupled framework. Martini et al. [2011] showed values of 0.20–0.50 Wm-2 in offline calculations for clear sky. Compared to aerosols, a factor of 100 smaller effect of ozone from LNOx. • Need realistic ozone in radiation schemes for longer simulations.

  21. Summary 2 • Mean O3 enhancement from LNOx is 22 ppbv, but more important is where the tropopause is located. Impact on UT temperatures is immediate (0.1 K). • Comparison with Beltsville ozonesonde is encouraging (good agreement with LNOx simulation), temperature biases are slightly decreased when interactive ozone is used. • Initial and boundary conditions are important. Convection was better represented in simulation driven by MERRA reanalysis than in simulation driven by NARR. Moreover, convective system entering WRF domain is captured only by the simulation driven by MERRA. • Hansen [2011] look-up table that uses mixed phase depth (measure of lapse rate) and convective precipitation is prone to model precipitation biases and vertical resolution. Advantage: no need to scale the modeled flash rate to observed flash rate. Day-to-day variations are slightly improved (correlation of 0.51 vs. 0.49) compared to approach of Allen and Pickering [2002].

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