1. A Chemical Characterization of North American Pollution Plumes over Europe 2. A 15-Year Climatology of Global Warm Conveyor Belt (WCB) Transport A. Stohl 1, H. Huntrieser 2, O. Cooper 3, S. Eckhardt 1, C. Forster 1, P. James 1, J. Heland 2, H. Mannstein 2, H. Schlager 2, B. Rappenglück 4, W. Junkermann 4, F. Arnold 5, H. Aufmhoff 5, S. Wilhelm 5 1 Technical University of Munich, Germany 2 DLR, Oberpfaffenhofen, Germany 3 NOAA Aeronomy Laboratory, Boulder, USA 4 Research Center Karlsruhe, Germany 5 Max-Planck Institute for Nuclear Physics, Heidelberg, Germany

Part 1: Aircraft measurements during CONTRACE Stohl et al., submitted to J. Geophys. Res. Aim of the first campaign in November 2001: To study the role of WCBs for intercontinental pollution transport Due to successful model forecasts, 3 North American plumes were encountered 3 cases were quite similar, only 1 case presented here

Tracer simulations using FLEXPART FLEXPART is a Lagrangian particle dispersion model no chemistry, only transport 3 carbon monoxide emission tracers (EDGAR) Asia Europe North America Stratospheric ozone tracer

Transport of North American CO tracer 13 November 2001: Accumulation of pollution in high-pressure system over North America FLEXPART total column of CO tracer GOES-East IR satellite image

Transport of North American CO tracer 15 November 2001: A low forms and opens an export pathway to the east in its warm sector: transport over high-emission regions FLEXPART total column of CO tracer GOES-East IR satellite image

Transport of North American CO tracer 17 November 2001: Cold front pushes pollution to the Atlantic Tracer plume and clouds are aligned in WCB Lifting to free troposphere FLEXPART total column of CO tracer GOES-East IR satellite image

Transport of North American CO tracer 18 November 2001: Pollution plume in the WCB outflow in the upper troposphere FLEXPART total column of CO tracer METEOSAT + GOES-East 5-day trajectories that ascend more than 5000 m during last 4 days

Transport of North American CO tracer 19 November 2001: Pollution plume arrives over Europe FLEXPART total column of CO tracer METEOSAT + GOES-East Falcon flight track

Meridional section through North America CO tracer along the flight track Northbound flight Southbound flight Munich to Stockholm Stockhom to Munich

Model tracers interpolated to the flight track Stratospheric O3 tracer + measured O3 + measured humidity +altitude (black) Asia CO tracer + measured NO y (black) +measured NO Europe CO tracer + measured CO 2 (black) North America CO tracer + measured CO (black)

Backward reconstruction of North American CO and NO y along flight track About 600 individual FLEXPART simulations every 200 m vertically every 0.1° along the track Advect unit mixing ratio backwards from aircraft position and calculate „residence times“ on a grid Multiply with emissions from EDGAR and obtain concentration at flight track

North American CO and NO y along flight track from 600 backward simulations EDGAR NO x + measured NO y (black) + measured NO EDGAR CO + measured CO (black) + aircraft altitude

FLEXPART backward simulation for peak at 11:53 UTC 27 second interval Residence time in whole atmospheric column Residence time in footprint

FLEXPART backward simulations for peak at 11:53 UTC Source contribution (ppb per grid cell)

Conclusions from Part 1 WCB transport is the key mechanism for fast intercontinental pollution transport Many chemical species were enhanced in the observed plumes CO CO 2 NO y (but 90% were removed due to washout) Ozone (even in November!) Acetone SO 2 Numerous hydrocarbons Lagrangian backward modeling allows quantitative determination of source contribution and resolves very small-scale features Don´t use „cheap“ trajectories to interpret „expensive“ aircraft measurements ! Stohl, A., S. Eckhardt, C. Forster, P. James, N. Spichtinger, and P. Seibert (2002): A replacement for simple back trajectory calculations in the interpretation of atmospheric trace substance measurements. Atmos. Environ. 36, (October issue)

Part 2: A 15-Year WCB Climatology Eckhardt et al., in preparation for J. Climate Basis: 360 million 6-day trajectories starting daily on a 1° x 1° global grid ECMWF ERA-15 re-analysis data WCB diagnosis by identifying trajectories that –ascend strongly and –travel northeastward during the first 48 hours

Frequency of WCB inflow: Strong contrasts between Northern and Southern Hemisphere: NH: maxima downwind of North America and Asia, winter maximum SH: less zonal variability, spring maximum

WCB transport 15-year climatology of WCB occurrence DAY 0

WCB transport 15-year climatology of WCB occurrence DAY 1

WCB transport 15-year climatology of WCB occurrence DAY 2

WCB transport 15-year climatology of WCB occurrence DAY 3

WCB transport 15-year climatology of WCB occurrence DAY 4

WCB transport 15-year climatology of WCB occurrence DAY 5

Climate variability and intercontinental transport Example: Influence of the North Atlantic Oscillation on WCBs NAO +NAO – At day 0 At day 2