1. TOPSE: Tropospheric Ozone Production About the Spring Equinox Elliot Atlas & TOPSE Science Team

2. Primary Objective of TOPSE To investigate the chemical and dynamic evolution of tropospheric chemical composition over mid- to high-latitude continental North America during the winter/spring transition, with particular emphasis on the springtime ozone maximum in the troposphere.

3. MeasurementInvestigators Remote Ozone/AerosolsBrowell et al., NASA Acidic Trace Gases/7-BeTalbot, Dibb, et al. UNH NMHC, Halocarbons, RONO 2 Blake et al., UCI NO 2, PeroxynitratesCohen, Thornton et al., UCB Speciated PeroxidesHeikes, Snow, URI OH, H 2 SO 4 Eisele, Mauldin, NCAR HO 2, RO 2 Cantrell, Stephens, NCAR HNO 3 Zondlo, NCAR NO x, NO y, OzoneRidley, Walega, NCAR CH 2 O, H 2 O 2 Fried, NCAR J values Shetter, Lefer et al., NCAR PAN, PPNFlocke, Weinheimer, NCAR CO, N 2 OCoffey, Hannigan, NCAR Ultrafine AerosolsWeber, GIT Mission Scientists/P.I.sAtlas, Cantrell, Ridley, NCAR TOPSE Investigators: Measurements

4. Modeling/CollaborationInvestigators Regional/Forecast Model (HANK)Klonecki, Hess et al., NCAR Global Model AnalysisTie, Emmons et al., NCAR (MOZART)Brasseur et al., MPI Process and Radiation ModelsMadronich, Stroud et al., NCAR Global Model/Process StudiesJacob, Evans, Harvard U. Stratosphere/Troposphere Exch.Allen, Pickering, U. Md. Regional/other ModelsWang et al., Rutgers U. Meteorological Forecast/Moody, Cooper, Wimmers, U.Va. Remote Sensing Ozonesonde NetworkMerrill, URI; Fast, PNWL GOME BrORichter, Burrows, U. Bremen Met. Forecasts (UT/LS)Newman, NASA Polar Sunrise Expt., 2000Shepson, Purdue; Bottenheim, Can. Met. Serv. TOPSE Investigators: Modeling/Collaboration

5. TOPSE Flight Tracks

6. Seasonal variation in trace gases/aerosols Evolution strong function of altitude and latitude Decline in NMHC; Spring maximum in sulfate PAN most significant odd-nitrogen component of NO y Ozone evolution in the mid-troposphere Increase about 20 ppb from Feb-May Covariation in PANs, aerosols; no PV trend Photochemical/surface sources implicated Surface ozone depletion Observations in early spring-May Br-catalyzed ozone loss Long-range transport of depleted air suggested Transport processes Most sampled air masses representative of background mid-troposphere Distant pollution sources were encountered in layers Some TOPSE Highlights

7. In-situ photochemical processes Measured radicals consistent with constrained models Hydrogen peroxide 2 – 10 x lower than model Formaldehyde photolysis significant HO X source at high latitudes Calculated increase in in-situ ozone production in spring from increasing HO X sources and NO Stratosphere-troposphere exchange Remote sensing (satellite/lidar) indicate folds/streamers/STE(?) In-situ encounters with lower stratosphere during flights 7-Be measurements/models suggest significant fraction of tropospheric ozone is from stratosphere. Seasonal modulation by photochemistry with contribution by STE Some TOPSE Highlights (cont’d)

8. Seasonal evolution of NMHC vs. latitude and altitude during TOPSE (Blake et al., UCI)

9. (Fried et al. – NCAR) Formaldehyde vertical distributions vs. latitude: Feb – May, 2000

10. (Scheuer, Talbot, Dibb – UNH) Evolution of Sulfate Aerosol Vertical Distribution 1 – 7 = Deployment number (Feb – May)

11. (Ridley, Walega - NCAR) Ozone vertical profile: Evolution during winter-spring

12. Deployment 1 Deployment 3 Deployment 6Deployment 5 Deployment 4 Deployment 7 Average Ozone Distributions During TOPSE (Browell et al., NASA)

13. (Cohen, Thornton – UCB Flocke, Ridley – NCAR) PANs and ozone in the mid-troposphere

14. (Dibb et al., UNH) 7 Be measurements diagnose stratospheric O 3 7 Be/O 3 correlation during TOPSE Observations of stratospheric influence: 7 Be, HNO 3, O 3

15. Chemical Transport Models (Global and Regional) Significant Model Differences: MOZARTHANK Domain GlobalNorth of 20 o Hor. Resolution 2 o x 1.9 o 243 km (Mercator proj.) Vert. Resolution 60 layers to 0.1 hPa38 layers to 100 hPa Meteorology ECMWFMM5 (NCEP) Stratospheric O 3 ClimatologicalRelaxed to P.V. Model Similarities: Chemical Mechanisms, Emissions, Dry Deposition, Washout, Lightning (Emmons, Hess, et al. – NCAR)

16. Average of O 3 for all flights All TOPSE flights: 40-85N, 235-300E, Surface to 350 hPa Good agreement between models and data until May

17. O 3 Budget: 30 o -90 o North, Surface-350 hPa MOZART, HANK PRODUCTION: HO 2 +NO->NO 2 +OH RO 2 +NO->NO 2 +RO DESTRUCTION: HO 2 +O 3 ->OH+2O 2 OH+O 3 ->HO 2 +O 2 H 2 O+O( 1 D)->2OH

18. O 3 Production and Loss Rates: 40-60N Comparison with Steady-State Model constrained by TOPSE observations (Cantrell) MOZART HANK SS-Model Prod. Loss

19. ODE DIAL observations of surface ozone depletion over Hudson Bay (Browell et al. – NASA)

20. (Ridley-NCAR; Blake-UCI; Talbot-UNH) In-situ measurements over Hudson Bay: Observations of surface ozone depletion

21. Transport of ozone depleted surface air from Arctic to Hudson Bay: Evidence from measurements, models, satellite

22. Summary TOPSE characterized seasonal evolution of ozone and precursors over continental N.America Seasonal and altitude dependent transport Siberia/Europe vs. Asia Ozone background has strong stratospheric source, but growth in spring is primarily from in-situ chemistry in troposphere O 3 /aerosol/precursor relationships 7 Be analysis/models (Surface ozone depletion widespread in Arctic…transport significant) Models capture many features of seasonal change after improvements from measurement comparison, but questions remain. Hydrogen peroxide Formaldehyde in UT etc….

23. TOPSE Science Team Engineers, technicians, staff and pilots of NCAR Research Aviation Facility Ground support at Churchill Airport and Thule Air Base Financial support of the National Science Foundation Atmospheric Chemistry Polar Programs NCAR Directors Fund Administrative and logistical support of the Atmospheric Chemistry Division, Traffic Services Acknowledgments