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TR AZOMOZA IC Comparison in the UTLS. Andreas Volz-Thomas and Martin G. Schultz. Uncertainties in the Global Tropospheric Ozone Budget. Objectives. Analyse observed and simulated trace gas concentrations relative to the tropopause

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Tr azomoza ic comparison in the utls

TRAZOMOZAICComparison in the UTLS

Andreas Volz-Thomas

and Martin G. Schultz

Uncertainties in the global tropospheric ozone budget
Uncertainties in the GlobalTropospheric Ozone Budget


  • Analyse observed and simulated trace gas concentrations relative to the tropopause

  • Analyse observed and simulated variability: seasonal pattern and interannual variability

  • Focus on Northern Mid-latitudes


  • identify model errors and the underlying cause (transport or chemistry?)

  • identify the bias in the MOZAIC data

Data selection for mozart
Data selection for MOZART

  • Simulations 1993-1998, 6-hourly „instantaneous“ values (20min time step)

  • European MOZAIC airports and surrounding columns (1.8° resolution); duplicate boxes removed

  • Latitude range 43°N-60°N (ozone similar within ±5 ppb)

  • Model results selected on model levels relative totropopause (dT/dz<2k/km)

Data selection for mozaic
Data selection for MOZAIC

O3: 8/94–6/03 (five A-340),

NOy and CO since 2001.

TP selection: 2 pvu

Level thickness from MOZART

TP: (p(PV=2) - 15 hPa) > p > (p(PV=2) - 15 hPa)

T+1 (LS): (p(PV=2) - 15 hPa) > p > (p(PV=2) - 45 hPa)

T-1 (UT): (p(PV=2) + 45 hPa) > p > (p(PV=2) + 15 hPa)

Results ozone
Results: Ozone



Sesonal variation of ozone

LS: ca. 100 ppb

TP: ca. 100 ppb

UT: ca. 50 ppb

Sesonal Variation of Ozone



Results noy
Results: NOy



Mozart with sampling bias of mozaic
MOZART with Sampling Bias of MOZAIC:

UT: 6+-6 ppb

TP: 19+-10 ppb

LS: 32+-14 ppb


  • MOZART reproduces the seasonal pattern of ozone well.

  • Some features of interannual variability are captured, but several features are missing: emissions (e.g. 1998), varying stratospheric ozone as main explanation.

  • It has a bias of about +50 ppb in UT and +100 ppb in LS

  • The sampling bias in MOZAIC (6 ppb in UT and 32 ppb in LS) explains about 20-30 % of the discrepancy.

  • The seasonal cycle of NOy in LS is anticorrelated with observations (erroneous strat. climatology!) and has a weaker seasonal amplitude. Wrong NOy/O3 ratio in LS.

  • Hypothesis: STE too weak(!) in MOZART 2, balanced by LS ozone bias. Chemistry also too weak?


  • Tests with "better" NOy climatology and lower O3 in LS

  • Test for TP selection (use PV for MOZART as well)

  • Look at MOZAIC CO as well

  • Same analysis for other areas

  • ...