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David Hirdman J.F. Burkhart, S. Eckhardt, H. Sodemann, A. Stohl Norwegian Institute for Air Research.

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Presentation on theme: "David Hirdman J.F. Burkhart, S. Eckhardt, H. Sodemann, A. Stohl Norwegian Institute for Air Research."— Presentation transcript:

1 David Hirdman J.F. Burkhart, S. Eckhardt, H. Sodemann, A. Stohl Norwegian Institute for Air Research

2 General motivation Deriving an improved method to identify potential source regions. General for different short-lived pollutants. Seasonal variability and evolvement over years/decades. Superior performance of LPDM’s compared with back-trajectories.

3 Methodology Back-trajectories PES-field (FLEXPART) Sources & sinks Anthropogenic & natural

4 New approach: 3-hourly backward simulations reaching 20 days back with the Lagrangian particle dispersion model (LPDM) FLEXPART. Output of FLEXPART: potential emission sensitivity fields indicate where emissions could have influenced a measurement. Measurement data from 4 Arctic stations. Statistical analyses of time periods up to 17 years long. Different species, e.g. tropospheric ozone, CO, EBC, sulphate.

5 Statistical analysis: Sort all the measurement data and consider either the highest or lowest 10%. Look at emissions sensitivity fields for the bottom 10% (“clean”) or top 10% (“dirty”) of the data.

6 Normalization with emission sensitivity fields for all measurement data. Values > 10% indicate that surface contact is enhanced, values < 10% indicate surface contact is less likely, relative to the entire data set. Statistical significance assured through bootstrap resampling and a 9-point smoothing function.

7 Results: Sulphate measured at Zeppelin 1991-2007 ”DIRTY” Top 10% ”CLEAN” Bottom 10%

8 Tropospheric ozone at Zeppelin, 1991-2007: ”HIGH” top 10%”LOW” bottom 10% WINTER (DJF)

9 Tropospheric ozone at Zeppelin, 1991-2007: ”LOW” bottom 10% SPRING (MAM) ”HIGH” top 10%

10 Tropospheric ozone at Zeppelin, 1991-2007: ”LOW” bottom 10% SUMMER (JJA) ”HIGH” top 10%

11 Tropospheric ozone at Zeppelin, 1991-2007: ”LOW” bottom 10% AUTUMN (SON) ”HIGH” top 10%

12 Common patterns between the different stations: Episodes of low ozone concentration during the Arctic spring. Alert SummitBarrow Zeppelin

13 Seasonal variation of EBC at Barrow: ”HIGH” Top 10% Spring WinterSummer Autumn

14 Conclusions: We make use of a new improved approach to pinpoint potential source regions for Arctic air pollution on a climatological basis. Strong seasonal variation in the potential source regions for tropospheric ozone at Alert, Barrow and Zeppelin. During high ozone episodes do we observe a decoupling from the boundary layer for all seasons but summer when Northern Eurasia gives a strong signal. Low ozone events show strong resemblance with the expected springtime depletion events, while nitrate titration plays a major role when no photochemical processes occur. Northern Eurasia is confirmed to be the dominating source region for EBC during the all seasons but summer when local sources dominate at Barrow.

15 Thank you!


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