Effects of Urban-Influenced Thunderstorms on Atmospheric Chemistry Kenneth E. Pickering Department of Meteorology University of Maryland HEAT Planning Workshop March 15, 2004

Outline Background – chemical measurements, modeling for deep convection, urban plumes, lightning NO x HEAT – proposed objectives, measurements, modeling strategies Possible activities

Effects of Deep Convection - Venting of boundary layer pollution - Transport of NO x, NMHCs, CO, and HO x precursors to upper troposphere - Downward transport of cleaner air - Transported pollutants allow efficient ozone production in upper troposphere - Results in enhanced upper tropospheric ozone production over broad regions -Increased potential for intercontinental transport - Enhanced radiative forcing by ozone

Effects of Deep Convection - Lightning production of NO - Perturbation of photolysis rates - Effective wet scavenging of soluble species - Incorporation of pollution aerosols into precipitation processes - Nucleation of particles in convective outflow - In remote regions low values of O 3 and NO x are transported to upper troposphere - Larger values of these species tranported to PBL where they can more readily be destroyed

Aircraft Measurements of Trace Gas Redistribution in Oklahoma PRESTORM June 15, 1985 MCC CO O3O3 Dickerson et al., 1987, Science

Pickering et al., 1990

Kansas-Oklahoma Squall Line Cell Goddard Cumulus Ensemble (GCE) Model with offline tracer transport

June PRESTORM Initial Conditions AltitudeCO (ppbv) O 3 (ppbv) NO x (pptv) km150 (245)28 (64)900 (2950) trop Urban BL values in parenthesesPickering et al. (1992) Representative of ~45 km downwind of Oklahoma City

Vertically-averaged Ozone Production in Cloud Outflow June PRESTORM (4-15 km) Cloud- UndisturbedProcessed Rural air Urban plume Values in ppbv/day Pickering et al. (1992)

LW Radiative Forcing - CloudsLW Radiative Forcing - Clear

The effect of thunderstorms on local O 3 can be remarkable even at periphery of storm.

On the third day of a high O 3 episode (June ), a line of thunderstorms passed just north of the Fair Hill, MD monitor.

Production of NO by Lightning - Global production estimates range from 2 to 20 Tg N/yr due to uncertainty in global flash rate and in the production per flash -Global flash rate estimated from OTD satellite measurement ~44 flashes/s (Christian et al., 2003) -Production per flash estimated from analysis of NO spikes in aircraft measurements, cloud-scale chemical transport modeling, or mass flux techniques -Cloud-scale chemical transport models represent lightning either through explicit electrophysics or use of observed/parameterized flashes -Models addressing other important questions: production per CG flash vs. production per IC flash; vertical distribution of lightning NOx at storm dissipation

July 12, 1996 STERAO-A Storm – NE Colorado

Cloud-scale Chemical Model Results - July 12, 1996 Transport Only – No chemistry or NO from Lightning DeCaria et al., 2000

CG: 460 IC:46 CG: 460 IC: 460 CG: 460 IC: 345 CG: 460 IC: 690 Moles NO Per Flash Model-simulated vs. Measured NOx Profiles For Four Lightning NO Production Scenarios DeCaria et al. (2000) For a 30-km flash, 460 moles NO/flash ~ 1 x molec/m

Ozone Production for 24 hours Following Storm 42 x 42 km anvil regionEntire model domain

(Huntrieser et al., 2002). a. b. EULINOX - July 21, 1998

1630 UTC1653 UTC 1734 UTC 1803 UTC Original Cell Cell Splitting Supercell Multicellular (Höller et al., 2000).

P CG = P IC = 250 moles/flash gives best agreement with Falcon measurements at 8.5 km of mean NO x ~ 3 ppbv

With 3 ppbv NO x in UT, ozone production is less efficient than in STERAO-A case with ~1.2 ppbv Max. ΔP(O 3 ) ~4 ppbv versus ~10 ppbv in STERAO-A case

HEAT Objectives Characterize and quantify convective transport of urban pollution from BL to UT Quantify lightning production of NO x Examine effects on UT chemistry (e.g., O 3, HO x production)

Objective 1 – Convective Transport Study transport and fate of urban pollutants Examine relative importance of convective motions, scavenging, and chemistry Measurements required – vertical profiles of chemical mixing ratios before, during and after storm (CO, NO, NO x, NO y, O 3, SO 2, HO x, HC, peroxides, aldehydes, acetone, aerosols) Characterize inflow, outflow, and storm core (?) U. of WY King Air – low level inflow, outflow WMI Lear Jet – anvil outflow Chemical analysis of precip from mesonet CO, CO 2 as tracers of air motion in storm

Objective 2: Production of Lightning NO x Quantify amount of NO produced per flash, per meter of flash channel, per thunderstorm, by different storm types Quantify amount produced by an IC flash vs. that produced by a CG flash and by different components of a flash Measurements required – NO, NO x, NO y in low level inflow/outflow, in anvil outflow, and in storm core (?). Channel lengths and distributions from lightning mapping system, CG flashes from NLDN Analysis of flash and aircraft NO spike meas.; chemical transport modeling; mass flux analysis

Objective 3: Effects on UT Chemistry Examine effects of combination of pollution and lightning NO x on UT O 3 and HO x chemistry Quantify relative contributions of boundary layer and lightning NO x to UT NO x mixing ratios Chemical transport modeling required To verify these models, chemical measurements needed in convective outflow plumes hours to days downstream

Possible Post-Mission Analysis and Modeling Activities Analysis of relationships between flash data and observed NO spikes Cloud-resolving model simulations of chemical transport, wet scavenging, lightning NO production (parameterized, explicit); comparisons with measurements and between models Tests of convective transport and lightning parameterizations in regional models; calculation of downstream ozone production