1. CLIMATE AND METEOROLOGY I: ATMOSPHERIC TRANSPORT

2. TOPICS FOR TODAY 1.How are changing transport patterns important for atmospheric composition? 2.Some robust transport changes 3.Changes in mid-latitude cyclones 4.Changes in the storm track (NAO) 5.El Nino and atmospheric transport

3. HOW ARE CHANGING TRANSPORT PATTERNS IMPORTANT FOR ATMOSPHERIC COMPOSITION? 1.Changing lifetimes of pollutants (longer at higher altitudes) 2.Changing vertical mixing, ventilation 3.Changing transport efficiency 4.Changing locations of down-wind impact 5.Changing winds affecting emission (dust, sea salt) ? ? Can impact tropospheric background and local pollution events

4. TOPICS FOR TODAY 1.How are changing transport patterns important for atmospheric composition? 2.Some robust transport changes 3.Changes in mid-latitude cyclones 4.Changes in the storm track (NAO) 5.El Nino and atmospheric transport

5. DISPLACEMENT AND INTENSIFICATION OF STORM TRACKS The JFM changes over the North Atlantic are associated with the mean position of the storm track shifting about 181 km northward Winter-time cyclone counts [Wang et al., 2006]

6. IMPORTANCE OF MID-LATITUDES CYCLONES IN AIR POLLUTION METEOROLOGY Clean air sweeps behind cold front Cold fronts from mid-latitude cyclones are the principal ventilation process for U.S. Midwest/Northeast, western Europe, China IPCC shows decrease in frequency, increase in intensity and a poleward shift of cyclones in 1950-2000 climatological data

7. TRENDS IN BLOCKING Blocking: persistent high-latitude ridging and displacement of mid-latitude westerly winds NH: “a significant trend toward weaker and less persistent events” Atlantic Europe W PacificE Pacific [Barriopedro et al., 2006]

8. NORTH ATLANTIC OSCILLATION (NAO) Many other modes of variability… Pacific Decadal Variability, Southern Annular Mode, Atlantic Multi-Decadal Oscillation… Can all impact relevant transport Dominant pattern of near-surface atmospheric circulation variability in N Atlantic, present throughout the year. Positive NAO index (MSLP Lisbon-Iceland) = enhanced westerly flow in winter (warmer maritime air over EU, dry conditions over S EU and N. Afr, also associated with a northeastward shift in Atlantic storm activity http://www.giub.unibe.ch/klimet/wanner/nao.html

9. WINDS & WAVES Trend in wave height (1950-2002) [IPCC, 2007] Affecting MBL chemistry, ocean emissions (DMS, sea salt…)?

10. EL NINO – SOUTHERN OSCILLATION (ENSO) Starts with the warming of tropical Pacific surface waters  global impact on T & precipitation (eg. 1997 ENSO  1998 highest global mean T on record, until 2005) Southern Oscillation Index: MSLP (Tahiti-Darwin) Correlation of SOI w/ TCorrelation of SOI w/ precip Links to drought and temperature…. [IPCC, 2007]

11. MONSOONS Monsoon: seasonal on-shore prevailing winds (generally bringing moisture) due to land-ocean T contrasts  Like a large sea-breeze effect Observed some diminished monsoonal circulations over the period of record, but little recent trend (uncertain record) Strength of monsoonal circulation is diagnosed by upper-level divergence (dotted line) [Chase et al., 2003]

12. TOPICS FOR TODAY 1.How are changing transport patterns important for atmospheric composition? 2.Some robust transport changes 3.Changes in mid-latitude cyclones 4.Changes in the storm track (NAO) 5.El Nino and atmospheric transport

13. EFFECT OF CLIMATE CHANGE ON REGIONAL STAGNATION Pollution episodes double in duration in 2050 due to decreasing frequency of cyclones ventilating the eastern U.S; expected result of greenhouse warming. 2045-2052 1995-2002 GISS GCM simulations for 2050 vs. present-day climate using pollution tracers with constant emissions Mickley et al. [2004] summer weather map illustrating cyclonic ventilation of the eastern U.S.

14. Stalled high pressure system increases ozone due to: increased biogenic emissions clear skies weak winds high temperatures. cold front EPA ozone levels 3 days later Cold front pushes smog poleward and aloft on a warm conveyor belt. cold front L L 85-104 ppb105-124 ppb cyclone Loretta Mickley (Harvard) EVOLUTION OF OZONE CONCENTRATIONS AS CYCLONE PASSES

15. CORRELATIONS AND TRENDS OF POLLUTION EPISODES AND CYCLONES IN THE NORTHEAST # pollution episode days (O 3 >80 ppb) and # cyclones tracking across SE Canada in summer 1980-2006 observations Cyclone frequency is predictor of pollution episode frequency. 1980-2006 decrease in cyclone frequency would imply a corresponding degradation of air quality if emissions had remained constant [Leibensperger et al. 2008] # cyclones # episodes

16. TOPICS FOR TODAY 1.How are changing transport patterns important for atmospheric composition? 2.Some robust transport changes 3.Changes in mid-latitude cyclones 4.Changes in the storm track (NAO) 5.El Nino and atmospheric transport

17. WINTER-TIME OZONE IN EU LINKED TO NAO Correlation between O 3 and the NAO  O 3 (high-low NAO) UK Unified Model simulation (shown to correspond well to TOMS O 3 ) Given observations [Hurrell et al., 1995] and predictions [Shindell et al., 1999] that there may be a positive trend in the NAO, we may expect ozone over parts of central and northern Europe to decrease, possibly enhancing an already existing negative trend (due to emission reductions. [Braesicke et al., 2003]

18. SPRING-TIME OZONE AT HIGH LATITUDE SITES IN EU AND NA CONTROLLED BY NAO (OR AO) Arctic Oscillation (AO) and North Atlantic Oscillation (NAO) are related MAM (sondes) JFM North America Europe In the NH spring, much of the year-to-year variability in tropospheric ozone is dynamically driven is not dominated by variations in ozone precursors emissions. Air quality improvements (associated with + NAO) extending to North America? [Lamarque and Hess, 2004]

19. TOPICS FOR TODAY 1.How are changing transport patterns important for atmospheric composition? 2.Some robust transport changes 3.Changes in mid-latitude cyclones 4.Changes in the storm track (NAO) 5.El Nino and atmospheric transport

20. ENSO AND OZONE INTERANNUAL VARIABILITY OVER EU Positive anomalies in tropospheric O 3 column and in surface O 3 are found over Europe in the spring following an El Nino year – linked to pollution transport from Asia and enhanced biomass burning. La Nina years El Nino years Ozone mass fluxes Southern Oscillation Index (SON) Tropospheric Ozone Column over EU (JFM) Surface Ozone over EU (JFM) [Koumoutsaris et al., 2008] R=-0.65 R=-0.50

21. EL NINO (NEGATIVE PHASE ENSO) MAY ALSO LEAD TO ENHANCED STE “ENSO affects global total tropospheric O 3 not only via its effects on chemical processes (temperature-dependent chemistry, water vapour concentrations, emissions, etc.) but also via its profound effect on STE in the extratropics.” [Zeng and Pyle, 2005]

22. EL NINO INFLUENCING NATURAL EMISSIONS [Stevenson et al., 2005]