Pathways for North American Outflow - Hindcast for ICART2 Qinbin Li, Daniel J. Jacob, Rokjin Park, Colette L. Heald, Yuxuan Wang, Rynda Hudman, Robert M. Yantosca Harvard University Mian Chin NASA/GSFC with support from NOAA Atmospheric Chemistry Program Hindcast for ICARTT, summer 2004. INTEX-NA, ITCT-2K4, ITOP etc.; the questions we ask: 1. what are the pathways for NA pollution outflow? 2. what chemical evolutions occur in the different outflow processes? 3. What can we learn from satellite observations on pollution outflow? 4. Any interannual variabilities in the outflow, for example, influence from El Nino on circulation? 5. Contributions from other continents to the NA outflow? ICART2 Planning Meeting, 1/21/2004 NOAA Aeronomy Lab, Boulder, CO

Model Simulations GEOS-CHEM Model Simulations Observations Global 3-D model of tropospheric chemistry-aerosols. Driven by GMAO GEOS-3 assimilated meteorology. Used in TRACE-P and ITCT-2K2 chemical hindcasts / forecasts and post-mission analyses. Model Simulations Time period: June-August of 1998, 2000, 2001, 2002 Tagged CO (all four years): 2°x2.5° (use 1998 FF and climatological BB emissions for all four years) Full-chemistry (2000 only): 1°x1° ‘nested’ over North America (use 2000 BB emissions) Observations MOPITT CO column MODIS aerosol optical depth AERONET aerosol optical depth Don’t want to bore you with details of the model; assimilated meteorology allows simulation of interannual variabilities and specific events; focus on summer; first general patterns of the outflow and any interannual variabilities; 1998-El Nino; 2004-latest observed SST trends and model forecasts indicate “neutral” to weak El Nino; focus on summer 2000, analysis of MOPITT CO column, MODIS and AERONET AOD.

Summer 2004: El Niño, La Niña, or Neutral? The most recent Niño 3.4 SST anomalies fall in the range of near-neutral conditions. Most of the statistical and dynamical model forecasts are indicating slightly above-average conditions over the coming several months. As we will show, El Nino could have impact on NA outflow. El Nino and La Niña episodes typically last approximately 9-12 months. They often begin to form during June-August, reach peak strength during December-April, and then decay during May-July of the next year.

GEOS-3 750 hPa Winds, 2000 H H Zonally-uniform flow pattern in June, while curve-like flow patterns in July and August. The circulation; a contrast between 2000 (close to “neutral”) v.s. 1998 (El Nino). Southward shift of jet stream in June 1998; H H

GEOS-3 750 hPa Winds, 1998 H H El Nino influence lasted into June; outflow in June at lower latitudes than other years. H H

GEOS-3 500 & 300 hPa Winds 300 hPa H 500 hPa H Recirculation in the middle and upper troposphere. 300 hPa H Recirculation in the middle to upper troposphere. 500 hPa H Recirculation in the middle to upper troposphere. We’ll come back to this.

North American Emissions Duncan et al. [2003] unit: 10-12 molec/cm2/s FF BB, June BB, July BB, August Climatology BB, July 2000 BB, August 2000: huge forest fires in NW (Montana, Idaho, Wyoming, etc.) Boreal forest fires v.s. unusually large forest fires in NW U.S. in July and particularly August 2000. Climatology: extensive boreal forest fires.

Horizontal N. American CO Flux, June 2000 Different latitudes in BB v.s. FF outflow. Lower latitudes outflow in June 1998. 1998 FF outflow at 35ºN-50ºN, BB outflow 45ºN-55ºN. Outflow at much lower latitudes in June 1998.

Horizontal N. American CO Flux, 2000 July Lower latitudes outflow in July than in June and August because of the subtropical troughs. August Outflow in July is at lower latitudes than in June. Outflow in August shows features in between June and July.

Vertical and Zonal N. American CO Flux, June 2000 1998 70ºW 300 hPa 70ºW 70ºW Lines – fluxes (vertical: 10-12 moles cm-2 s zonal: 10-9 moles cm-2 s) Color contours – concentrations (ppb) (1) BL and lower FT outflow. (2) Convective outflow in MT/UT.

Vertical and Zonal N. American CO Flux, July 70ºW 300 hPa 70ºW 70ºW Lines – fluxes (vertical: 10-12 moles cm-2 s zonal: 10-9 moles cm-2 s) Color contours – concentrations (ppb) Stronger convective transport than June and August.

Vertical and Zonal N. American CO Flux, August 70ºW 300 hPa 70ºW 70ºW Lines – fluxes (vertical: 10-12 moles cm-2 s zonal: 10-9 moles cm-2 s) Color contours – concentrations (ppb)

Event June 9-13: BL, WCB and Convective Outflow GOES IR AERONET

Event June 9-13: WCB, Convection from Midwest from southeast

Event July 2-7: Outflow at Low Latitude Mopitt only July 2-3, no data for July 4-14; what is the freq of MOPITT, MODIS? Ask wife GOES IR AERONET

Event July 2-7: Outflow at Low Latitude Enhanced CO. Enhanced ozone and aerosols.

Recirculation in the Upper Troposphere North American Fossil Fuel CO 270 hPa, July 6-23, 2000 Deep convection in the south-central U.S. followed by recirculation in the MT and UT; fairly aged air masses with high ozone but depleted NOy and aerosols upon leaving the continental U.S. (animation)

Event July 9-14: Recirculation AERONET GOES IR

Event July 9-14: Recirculation Enhanced CO in the upper troposphere. Enhanced ozone in the upper troposphere. Aerosols are depleted.

Asian and European Influences Detectable? Asian and European influences dispersed into the background. Asian plumes could be seen in strong transpacific transport. > 40 ppbv

N. American Biomass Burning CO, 500 hPa August 2000 Plumes from the huge fires in the northwest US are lifted to 5-8 km by convection and then exported (1) northeastward north of 50ºN (2) eastward by the westerly at 40-50ºN (3) southeastward at 30-45ºN and impacts much of the middle and east U.S. (animation)

N. American Fossil Fuel CO, 850 hPa July, 2000

N. American Fossil Fuel CO, 500 hPa July, 2000

N. American Fossil Fuel CO, 300 hPa July, 2000

Summary and Conclusions Main pathways: BL and lower FT outflow; Convective outflow in the MT and UT. Outflows occur at a rather large latitude range (30ºN-55ºN) along the east coast. Deep convections in the south-central U.S. are often followed by recirculation in the MT and UT over much of the U.S. Biomass burning outflows generally occur at higher latitudes (45ºN-55ºN) than anthropogenic outflows. Outflows occur at lower latitudes in July and August than in June due to more curve-like flow patterns in July and August. MOPITT CO columns and MODIS and AERONET aerosol optical depths provide useful insights in understanding N. American pollution outflow.