1. Lu Hu lu.hu@umontana.edu
Global budget of tropospheric ozone: long-term trend and recent model advances
Lu Hu
With
Loretta Mickley, Daniel Jacob, Xiong Liu, Patrick Kim, Yi Zhang, Lin Zhang, Bob Yantosca, Melissa Sulprizio
Acknowledgement: WOUDC, NOAA-GMD, MOZAIC-IAGOS, NASA GMAO, ACMAP, and Aura Science Team

2. GEOS-Chem updates in past decade have led to more active tropospheric ozone chemistry
Global tropospheric ozone budget in GEOS-Chem benchmark outputs
Model release date
Changes mainly reflect model advances, not the actual atmosphere
Hu et al. Atmos. Environ., in review

3. GEOS-Chem updates in past decade have led to more active tropospheric ozone chemistry
Global tropospheric ozone budget in GEOS-Chem benchmark outputs
Same met and emis year
10 years later
Model release date
Changes mainly reflect model advances, not the actual atmosphere
Hu et al. Atmos. Environ., in review

4. GEOS-Chem v10-01 provides the best simulation of global tropospheric ozone over the history of the GEOS-Chem model versions
Mean 500 hPa ozone in JJA 2013
OMI satellite data, X. Liu, SAO
Model
Hu et al. Atmos. Environ., in review

5. GEOS-Chem v10-01 provides the best simulation of global tropospheric ozone over the history of the GEOS-Chem model versions
Mean 500 hPa ozone in JJA 2013
OMI satellite data, X. Liu, SAO
Model
But, GEOS-Chem shows a negative bias relative to ozonesondes at high northern latitudes, also a large sensitivity to meteorological fields
Ozonesonde GEOS-5 (0.25° aka GEOS-FP) GEOS-5 (0.5°) GEOS-4 (1°)
Pressure (hPa)
Ozone (ppbv)
Hu et al. Atmos. Environ., in review

6. Tropospheric ozone budget in current models
Burden (Tg)
Chemical production (Tg/y)
Stratosphere-troposphere exchange (Tg/y)
Pre 2000
Post 2010
Hu et al. Atmos. Environ., in review

7. Tropospheric ozone budget in current models
GEOS-Chem
Burden (Tg)
Chemical production (Tg/y)
Stratosphere-troposphere exchange (Tg/y)
Pre 2000
Post 2010
Hu et al. Atmos. Environ., in review

8. Tropospheric ozone budget in current models
GEOS-Chem
Burden (Tg)
Chemical production (Tg/y)
Stratosphere-troposphere exchange (Tg/y)
Pre 2000
Post 2010
Hu et al. Atmos. Environ., in review

9. Models can reproduce present-day levels, but not multi-decadal trends
Increasingly active tropospheric chemistry in models would affect the computed sensitivity to perturbations
GEOS-Chem simulation with MERRA+MACCity
Climate models
Model
O3 (ppbv)
Observations
Observations
Parrish et al., 2014
Hu et al. in prep
Models can reproduce present-day levels, but not multi-decadal trends

10. A widespread model ozone overprediction in 1980s
O3 (ppbv)
WE also have looked at the ozonesonde data in 1980s, and it generally shows the same thing.
Lack of information on emission over time
Hu et al. in prep

11. Model estimates of natural background ozone is way too high, not only in 1920s, but also 1980s …
Observations
If no anthropogenic emissions in the model
Hu et al. in prep

13. Nature sources Climate models Model O3 (ppbv) Observations
GEOS-Chem simulation with MERRA+MACCity
Climate models
Model
O3 (ppbv)
Observations
Observations
If no anthropogenic emissions in the model
Parrish et al., 2014
Need to reduce global NOx emission in 1980s by half?
Hu et al. in prep