1. TEMIS user workshop, Frascati, 8-9 October 2007 Long range transport of air pollution service: Part 1: Trajectories Bart Dils, M. De Mazière, J. van Geffen, M. Van Roozendael

2. TEMIS user workshop, Frascati, 8-9 October 2007 Introduction Air pollution is not only a local problem: highlights Stohl et al. 2003 –During favourable conditions intercontinental transport can occur on a very small timescale (~1 day!) –This allows transport of short-lived species such as NO 2 Li et al. (JGR 2002) using GEOS-CHEM model –O 3 : average 5 ppbv, up to 20 ppbv during transport events. –In 1997 20% of O 3 EU threshold violations (55 ppbv, 8-hour average) would not occur without transport! –86% = direct O 3 transport, 14% due to precursors (NOx and PAN)

3. TEMIS user workshop, Frascati, 8-9 October 2007 Introduction:monitoring Transport can occur over small timescales –High temporal resolution NO2 lifetime is short => concentration are low –sharp detection limit –High signal to noise ratio Transport simulations can fill in the gaps & add value to the observations FLEXPART developed by Andreas Stohl

4. TEMIS user workshop, Frascati, 8-9 October 2007 Trajectories: FLEXPART FLEXPART is a Lagrangian particle dispersion model which computes the trajectories of a large number of infinitesimally small air parcels to describe the transport and diffusion of tracers in the atmosphere relatively fast computation times FLEXPART simulates transport, turbulence, dry and wet deposition, and radioactive (or other) decay Freely available on: http://zardoz.nilu.no/~andreas/flextra+flexpart.html

5. TEMIS user workshop, Frascati, 8-9 October 2007 FLEXPART:: Input Windfield data from ECMWF –1°x1°, 3hourly NOx emission data from EDGAR 3.2 FT2000 –Yearly mean 1°x1°, 500 highest emission grids within 110°E to 50°E & 15°N to 65°N –No emissions from Europe included! FLEXPART control parameters –Atmospheric half-lifetime is set to 2 days

6. TEMIS user workshop, Frascati, 8-9 October 2007 FLEXPART:: Output 1°x1° lat-lon grid, 10 vertical levels (1km resolution) 3h averages every 3 hours (15:00UT is plotted as it corresponds with the transatlantic overpass-time of OMI) Plot1: Total columns (molec/cm 2 ) in Lon-Lat domain Plot2: Lon-Altitude plot, highest concentration (molec/cm 3 ) along each Longitudinal band

7. TEMIS user workshop, Frascati, 8-9 October 2007 FLEXPART:: Example 1 Plot1: Total columns (molec/cm 2 ) in Lon-Lat domain

8. TEMIS user workshop, Frascati, 8-9 October 2007 FLEXPART:: Example 2 Plot2: Maximal concentration (molec/cm 3 ) along the Longitudinal band

9. TEMIS user workshop, Frascati, 8-9 October 2007 Trajectories: Limits Yearly averaged NOx emission as a representative for time dep. NO 2 emissions Uniform NOx half-lifetime over entire domain –No chemistry or Temperature/Altitude dependence! Wind field errors & limited resolution Interpolation errors –wind data are only available at discrete locations in time and space Truncation errors

10. TEMIS user workshop, Frascati, 8-9 October 2007 Trajectories: Future Improvements Better NOx emission climatology Better NOx half-lifetime parameter –Detailed OMI FLEXPART intercomparison Forecasting abilities using either ECMWF or GFS windfield data Seasonality and Receptor-region analysis

11. TEMIS user workshop, Frascati, 8-9 October 2007 Trajectories: Summary FLEXPART output generates a useful tool to visualise and (eventually) predict LRT events One should keep in mind the inherent limitations of this product The real strength of these simulations lie in their synergic use with OMI (or other satellites) data products –(More on this during Bas’ presentation)