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CLIMATE AND METEOROLOGY I: ATMOSPHERIC TRANSPORT

CLIMATE AND METEOROLOGY I: ATMOSPHERIC TRANSPORT . TOPICS FOR TODAY. How are changing transport patterns important for atmospheric composition? Some robust transport changes Changes in mid-latitude cyclones Changes in the storm track (NAO) El Nino and atmospheric transport.

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CLIMATE AND METEOROLOGY I: ATMOSPHERIC TRANSPORT

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  1. CLIMATE AND METEOROLOGY I:ATMOSPHERIC TRANSPORT

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

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

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

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

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

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

  8. NORTH ATLANTIC OSCILLATION (NAO) 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 Many other modes of variability… Pacific Decadal Variability, Southern Annular Mode, Atlantic Multi-Decadal Oscillation… Can all impact relevant transport

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

  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/ T Correlation 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 Strength of monsoonal circulation is diagnosed by upper-level divergence (dotted line) Observed some diminished monsoonal circulations over the period of record, but little recent trend (uncertain record) [Chase et al., 2003]

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

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

  14. EVOLUTION OF OZONE CONCENTRATIONS AS CYCLONE PASSES 85-104 ppb 105-124 ppb 3 days later Cold front pushes smog poleward and aloft on a warm conveyor belt. cyclone EPA ozone levels • Stalled high pressure system increases ozone due to: • increased biogenic emissions • clear skies • weak winds • high temperatures. cold front L cold front L Loretta Mickley (Harvard)

  15. CORRELATIONS AND TRENDS OF POLLUTION EPISODES AND CYCLONES IN THE NORTHEAST # pollution episode days (O3>80 ppb) and # cyclones tracking across SE Canada in summer 1980-2006 observations # cyclones # episodes 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]

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

  17. WINTER-TIME OZONE IN EU LINKED TO NAO UK Unified Model simulation (shown to correspond well to TOMS O3) Correlation between O3 and the NAO O3 (high-low NAO) 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 North America Europe MAM (sondes) JFM 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 • How are changing transport patterns important for atmospheric composition? • Some robust transport changes • Changes in mid-latitude cyclones • Changes in the storm track (NAO) • El Nino and atmospheric transport

  20. ENSO AND OZONE INTERANNUAL VARIABILITY OVER EU Ozone mass fluxes La Nina years Southern Oscillation Index (SON) R=-0.65 Tropospheric Ozone Column over EU (JFM) El Nino years R=-0.50 Surface Ozone over EU (JFM) Positive anomalies in tropospheric O3 column and in surface O3 are found over Europe in the spring following an El Nino year – linked to pollution transport from Asia and enhanced biomass burning. [Koumoutsaris et al., 2008]

  21. EL NINO (NEGATIVE PHASE ENSO) MAY ALSO LEAD TO ENHANCED STE “ENSO affects global total tropospheric O3 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]

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