1 / 20

S.Rast(1), M.G.Schultz(2)

A modelling study on trends and variability of the tropospheric chemical composition over the last 40 years. S.Rast(1), M.G.Schultz(2) (1) Max Planck Institute for Meteorology, Bundesstr. 53, D-20146 Hamburg, Germany (2) ICG-II, Forschungszentrum J ülich, D-52425 Jülich, Germany.

laasya
Download Presentation

S.Rast(1), M.G.Schultz(2)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. A modelling study on trends and variability of the tropospheric chemical composition over the last 40 years S.Rast(1), M.G.Schultz(2) (1) Max Planck Institute for Meteorology, Bundesstr. 53, D-20146 Hamburg, Germany (2) ICG-II, Forschungszentrum Jülich, D-52425 Jülich, Germany

  2. The RETRO project Primary objective: understand, detect and assess long-term changes and interannual variability of the tropospheric chemical composition over the last 40 years (1960-2000).

  3. The Global Circulation Chemistry Transport Model ECHAM5-MOZ • Based on global circulation model ECHAM5 • Tropospheric chemistry comprises 63 transported species and 168 reactions (chemistry of MOZART2.4) • ERA40 analysis is used for driving the atmosphere dynamics • Spectral resolution: T42L31 (about 2.8ºx2.8º, upper limit 10 hPa) • Tracers undergo: advection, vertical diffusion, dry deposition, chemical reactions, wetdeposition, emissions

  4. RETRO Emissions - Other Anthropogenic Emissions • Anthropogenic emissions increase • CO and NOx emissions are quantitatively the most • important anthropogenic emissions

  5. Natural Emissions from Vegetation (MEGAN) I Isoprene Terpene f(T, ) f(T) • Large interannual variability in the tropics (Latin America) • High values of emissions in warm years (1998)

  6. Lightning Emissions • Lightning emissions do not show a tendency for the GCM-chemistry models MOZECH and LMDz • Strong increase in lightning emissions for CTM TM4

  7. ECHAM5 – water budget ERA40

  8. Lightning Emissions - Correlation • Correlation is generally low: R=0.1 (MOZECH-LMDZ) • R=0.2 (MOZECH-TM4)

  9. Mass of troposphere Mass of troposphere using the meteorological tropopause is slightly increasing by +0.7% (global warming leads to higher tropopause) • Mass of troposphere using the chemical tropopause (150ppbv O3) is slightly decreasing by -0.5% (ozone concentration is in general increasing) • Chemical tropopause is below the meteorological tropopause in contrast to literature (Wu et al.)

  10. Mass weighted OH concentration in troposphere • OH is mainly located in lower and middle troposphere  no difference between chemical and meteorological tropopause • Mean concentration (12.9±0.1)105 molec/cm3 (Spivakovsky et al. (2000): 11.6 105 molec/cm3, Poisson et al. (2000): 12.4 105 molec/cm3) • No longterm tendency

  11. Lifetime of Methane • Lifetime of methane using model methane concentration and meteorological tropopause • Total lifetime includes a constant soil sink of 30Tg/yr and stratospheric sink of 40Tg/yr. • Trend in total lifetime:  0 • Stevenson found a total lifetime of (8.67±1.32) yr (2006).

  12. The Ozone budget Ozone budget is calculated by P+L+S+D=Δ P (0): Ozone production rate L (0): Ozone loss rate S ( 0): Inferred stratospheric influx D (0): Dry deposition rate Δ: Rate of change in ozone burden Δ (1.2 to 1.6) Tg/yr  can be neglected S P L D

  13. Ozone burden Ozone burden: about 10% difference between chemical and meteorological tropopause Correlation R=0.987 Warm years have extra hight ozone burden (1998), increase about 20% over 41 years Δ=1.6Tg/yr met. tropopause Δ=1.2Tg/yr Ozone chem. tropopause Δ=0.9Tg/yr Δ=0.5Tg/yr Ozone from stratosphere

  14. Time series analysis Seasonal trend decomposition based on Loess time series analysis: • Decompose time series in a trend, a seasonal component and a remainder • Trend: long term trend over several years • Seasonal component: Seasonal variation and its changes over the years • „white noise“ remainder • (R.B.Cleveland et al., 1990)

  15. Time series decomposition for ozone production and loss Monthly O3 production Tg/month Seasonal component Trend component Remainder (Negative) monthly O3 loss Tg/month Seasonal component Trend component Remainder

  16. Ozone production and loss • Trend in ozone production: (26.3±6.4)Tg/yr2 • Trend in ozone loss: -(24.6±6.4)Tg/yr2 • Warm years (1998) show higher chemical activity • No significant trend in seasonality

  17. Time series of dry deposition of ozone Monthly O3 dry deposition Tg/month Seasonal component Trend component Remainder • Ozone dry deposition trend: (3.13±0.73)Tg/yr2 • Correlation with ozone burden: R=0.96

  18. 2000 Summary of variability patterns

  19. Comparison with other models Short comparison with values given by Stevenson (2006). Mean values of 25 models which are representative for the year 2000 Stev. MOZ

  20. Conclusion • Natural emissions are rather constant (climate variability more important than climate change) • Global mass weighted OH concentration has no trend • Methane lifetime has a trend with respect to OH. Must be due to tempereature change and/or changes in OH distribution • Ozone burden increase about 20% over 41 years, decoupled from OH?

More Related