1. Diagnosing the sensitivity of O 3 air quality to climate change over the United States Moeko Yoshitomi (moeko@fas.harvard.edu), Daniel J. Jacob, Loretta J. Mickley, Philippe Le Sager, Julia M. Sygiel, Shiliang Wu Department of Earth & Planetary Sciences Harvard University presented at GCAP Phase 2 Science Team Meeting Harvard University, MA, US October 12 th, 2007

2. [2] CMU CTM Projecting Future O 3 Air Quality in the US [1] Harvard CTM [Wu et al., 2007] Δ(2050s － present) in simulated summer daily 8-hr max O 3 levels [Racherla and Adams, 2006] O 3 [ppb] ・ Many regions show substantial future O 3 increases (1-5 ppb) due to climate change ・ Spatial patterns of climate-induced increases in O 3 is different - where the highest O 3 is predicted - how much O 3 increases at a maximum

3. [2] CMU CTM Projecting Future O 3 Air Quality in the US [1] Harvard CTM [Wu et al., 2007] Δ(2050s － present) in simulated summer daily 8-hr max O 3 levels [Racherla and Adams, 2006] O 3 [ppb] Key issue: modeling of the fate of isoprene emissions over the SE isoprene emission Higher isoprene emissions in SE ⇒ O 3 ↑ or ↓??? [10e-8 g C/m 2 /s] [g/s]

4. Isoprene k 298 =1.3x10 -17 RONO 2 (isoprene nitrate) OH RO 2 NO Isoprene NO 2 k 298 =1.0x10 -10 O 3 ↑ O3O3 Products O 3 ↓ Deposition Uncertain NOx-Isoprene-O 3 Chemistry NO O 3 ↓ There is a controversial competition on isoprene effects on O 3 branch ratio?? NOx recycled ??

5. Hourly surface O 3 concentrations from AIRS/EPA and daily maximum temperatures from NCDC, for JJA 1980-1998, which is gridded at 4x5 Observations [1] GCAP run at 4x5 resolution = GEOS-Chem + calculated GISS GCM meteorology (JJA 1999-2001) [2] GEOS-4 run at 2x2.5 resolution = GEOS-Chem + assimilated GEOS4/GMAO meteorology (JJA 1999-2001) Model Simulations Major Questions from Previous GCAP Research 1. Can we apply observed O 3 -temperature relationship to validate chemical models used to investigate the sensitivity of surface O 3 to climate change? 2. Is the O 3 -temperature relationship sensitive to assumptions about the fate of isoprene nitrate? Understanding the Relationship of Surface O 3 and Temperature

6. Reduced-major-axis (RMA) linear regression: to allow for errors in both x and y coordinates Data Sets ・ Daily maximum of 8-hr running average O 3 concentrations (MDA8) ・ Daily maximum temperature Regression Analysis on O 3 and T Approach [For Question 1 & 2] Analyze the relationship in a gridbox-scale [For Question 2] Analyze the relationship in a regional scale (Northeast: 7 boxes, Southeast: 9 boxes, Midwest, Northwest, Southwest, Central, Mid-Atlantic)

7. From RMA linear regression ・ Sensitivity of O 3 to temperature varies across the US ・ The NE shows stronger O 3 /T correlation than the SE Observed Correlation between O 3 and T -10 5 0 5 10 Correlation Coefficient Slope dO 3 /dT -1 -.5 0.5 1

8. From RMA linear regression ・ Sensitivity of O 3 to temperature varies across the US ・ The NE shows stronger O 3 /T correlation than the SE Observed Correlation between O 3 and T -10 5 0 5 10 Correlation Coefficient Slope dO 3 /dT -1 -.5 0.5 1 SE NE

9. O 3 and Temperature Observed by AIRS Temperature has an inter-annual variability - 19-yr mean/1988 mean/1992 mean; NE: 300.53/302.14/298.79 [K], SE: 305.92/306.10/305.26 [K] 280 300 320 T max [K] 280 300 320 T max [K] 150 100 50 0 150 100 50 0 150 100 50 0 MDA8 [ppb] 150 100 50 0

10. O 3 and Temperature Simulated by GCAP 280 300 320 150 100 50 0 MDA8 [ppb] 280 300 320 T max [K] 150 100 50 0 280 300 320 150 100 50 0 280 300 320 150 100 50 0 MDA8 [ppb] NE has stronger O 3 /T correlation than SE - GCAP O 3 /T correlations are slightly stronger in both NE and SE than observed O 3 /T correlations The GCAP results do not vary too much year-to-year

11. GCAP Model Captures Correlation Trends -1 -.5 0.5 1 1980-1998 obs 1999-2001 GCAP 1999-2001 GEOS4 ・ GEOS4 does not show the difference between NE and SE that obs. and GCAP model show ・ Sensitivity of O 3 to temperature varies across the US in both obs. and models ・ Both the observations and GCAP show stronger correlation in the NE than the SE

12. GCAP Captures the Variation in dO 3 /dT Slope Slope of dO 3 /dT from RMA linear regression -10 5 0 5 10 1980-1998 obs 1999-2001 GCAP 1999-2001 GEOS4 ・ Cool Gulf of Mexico air with low-level O 3 gives higher slopes in the SE; nothing to do with local chemistry ・ GEOS4 does not show the difference between NE and SE that GCAP shows

13. [Short-term work] ・ Explore reasons for the differences in O 3 -T correlation between obs. and models - meteorology issue (e.g., difference between GCAP and GEOS4) - missing chemistry (e.g., isoprene sensitivity analysis) ・ Interpret whether the NE-SE contrast reflects transport or chemistry [Long-term work] ・ Estimate the sensitivity of ozone pollution to future global change with our GCAP model for each SRES scenario ・ Investigate effects of 2000-2050 changes in global anthropogenic emissions and in general circulation to the intercontinental transport of air pollutants to the US My Future Work

14. GCAP Phase 2 Science Team meeting at Maxwell Dworkin 223

15. GCAP Phase 2 Science Team meeting at Maxwell Dworkin 223

16. GCAP Phase 2 Science Team meeting at Maxwell Dworkin 223

17. GCAP Phase 2 Science Team meeting at Maxwell Dworkin 223