1. FACTORS CONTROLLING TROPOSPHERIC OZONE AND ITS COUPLING FROM REGIONAL TO GLOBAL SCALES
Daniel J. Jacob
Harvard University
with support from NASA, NOAA, EPA, EPRI

2. GLOBAL BUDGET OF TROPOSPHERIC OZONE
Global sources and sinks, Tg O3 yr-1 (GEOS-CHEM)
Chem prod in troposphere
4900
Chem loss in troposphere
4200
Transport from stratosphere
500
Deposition
1200 O2 hn O3
STRATOSPHERE
8-18 km
TROPOSPHERE hn
NO2 NO O3
hn, H2O OH
HO2
H2O2
Deposition
CO, VOC

3. TREND IN TROPOSPHERIC OZONE BACKGROUND AT NORTHERN MIDLATITUDES
Observations from European mountain sites [Marenco et al., 1994]

4. THIS OZONE BACKGROUND IS A LARGE INCREMENT TOWARDS VIOLATION OF AIR QUALITY STANDARDS
Europe
(8-h avg.)
Europe
(seasonal)
U.S.
(8-h avg.)
U.S.
(1-h avg.)
ppbv
preindustrial
present
background

5. GLOBAL TRANSPORT OF TROPOSPHERIC OZONE AROUND THE NORTHERN MIDLATITUDES POLLUTION BELT
Ozonesonde and MOZAIC observations at 400 hPa, July 1997
Li et al. [2001]
How does this intercontinental transport of ozone contribute to regional air quality issues?

6. SUMMER 1995 MEAN AFTERNOON OZONE IN SURFACE AIR
Fiore et al. [2002a]
AIRS observations
GEOS-CHEM model
(r2 = 0.4, bias=3 ppbv)
“Background ozone” produced outside the North American boundary layer
contributes ppbv to mean surface air concentrations in the model

7. SURFACE OZONE ENHANCEMENTS OVER U. S
SURFACE OZONE ENHANCEMENTS OVER U.S. IN SUMMER DUE TO ASIAN & EUROPEAN ANTHROPOGENIC EMISSIONS Global 3-D model results (GEOS-CHEM) sampled for ensemble of summer days over the U.S.
tropical
air
Subsidence of Asian pollution
+ local production
stagnation
U.S. standard
European standards
Fiore et al. [2002a]

8. NORTH AMERICAN OZONE OUTFLOW IN SURFACE AIR (GEOS-CHEM model results for 1997)
APRIL H L
JULY H
Li et al. [2002a]

9. TRANSPORT OF U.S. OZONE POLLUTION TO BERMUDA IN SPRING
Observations
(S. Oltmans)
GEOS-CHEM
model
(S. Oltmans)
Most of surface ozone over Bermuda in spring originates from the U.S.; stratosphere contributes less than 5 ppbv
Li et al. [2002b]

10. OZONE AT MACE HEAD, IRELAND (Mar-Aug ’97)
North American pollution events enhance ozone by 5-15 ppbv
Observed
[Simmonds]
GEOS-CHEM
model
N.America pollution
events in model
Li et al. [2002b]

11. TRANSPORT OF U.S. POLLUTION TO EUROPE: CORRELATION WITH THE NAO INDEX
NAO index = normalized surface P anomaly between Iceland and Azores
North Atlantic Oscillation (NAO) Index
North American ozone pollution enhancement
At Mace Head, Ireland (GEOS-CHEM model)
r = 0.57
Li et al.
[2002a]
Greenhouse warming a NAO index shift a change in transatlantic
transport of pollution

12. SPRINGTIME ENHANCEMENT OF OZONE OVER ASIA DUE TO EUROPEAN ANTHROPOGENIC EMISSIONS
GEOS-CHEM model results at 900 hPa, March-May 1996
Liu et al.
[2002]

13. Fossil fuel NOx emissions Methane concentration
Combined effects of future anthropogenic emission trends on U.S. ozone air quality and on global climate
Ozone pollution
50% NMVOC
1995 (base)
50% CH4
50% NOx
2030 A1
2030 B1
IPCC scenario
Fossil fuel NOx emissions
(2020 vs. present)
Global U.S.
Methane concentration A1
+80%
-30%
+35% B1
+10%
-60%
+20%
Fiore et al.
[2002b]

14. NOx EMISSIONS (Tg N yr-1) TO TROPOSPHERE
STRATOSPHERE
0.2
LIGHTNING
5.8
FOSSIL FUEL
23.1
SOILS
5.1
BIOMASS
BURNING
5.2
BIOFUEL
2.2
AIRCRAFT
0.5

15. OZONE POLLUTION IN THE UNITED STATES
90th percentiles of summer afternoon (1-5 pm)
surface ozone concentrations (ppbv),
Fiore et al. [1998]