Diagnosing the sensitivity ofO3 air quality

to climate changeover 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 SciencesHarvard University

presented at GCAP Phase 2 Science Team MeetingHarvard University, MA, US

October 12th, 2007

[2] CMU CTM

Projecting Future O3 Air Quality in the US

[1] Harvard CTM[Wu et al., 2007]

Δ(2050s － present) in simulated summer daily 8-hr max O3 　 levels

[Racherla and Adams, 2006]

O3 [ppb]

・ Many regions show substantial future O3 increases (1-5 ppb) due to climate change・ Spatial patterns of climate-induced increases in O3 is different

- where the highest O3 is predicted - how much O3 increases at a maximum

[2] CMU CTM

Projecting Future O3 Air Quality in the US

[1] Harvard CTM[Wu et al., 2007]

Δ(2050s － present) in simulated summer daily 8-hr max O3 　 levels

[Racherla and Adams, 2006]

O3 [ppb]

Key issue: modeling of the fate of isoprene emissions over the SE

isopreneemission

Higher isoprene emissions in SE ⇒ O3 ↑ or ↓???

[10e-8 g C/m2/s] [g/s]

Isoprenek298=1.3x10-17

RONO2

(isoprene nitrate)

OH RO2

NO

Isoprene

NO2

k298=1.0x10-10

O3 ↑

O3 Products O3 ↓

Deposition

Uncertain NOx-Isoprene-O3 Chemistry

NO

O3 ↓

There is a controversial competition on isoprene effects on O3

branch ratio??branch ratio??

NOx recycled ??NOx recycled ??

Hourly surface O3 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 O3-temperature relationship to validate chemical models used to investigate the sensitivity of surface O3 to climate change?2. Is the O3-temperature relationship sensitive to assumptions about the fate of isoprene nitrate?

Understanding the Relationship of Surface O3 and Temperature

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 O3 concentrations (MDA8)・ Daily maximum temperature

Regression Analysis on O3 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)

From RMA linear regression

・ Sensitivity of O3 to temperature varies across the US・ The NE shows stronger O3/T correlation than the SE

Observed Correlation between O3 and T

-10 5 0 5 10

Correlation CoefficientSlope dO3/dT

-1 -.5 0 .5 1

From RMA linear regression

・ Sensitivity of O3 to temperature varies across the US・ The NE shows stronger O3/T correlation than the SE

Observed Correlation between O3 and T

-10 5 0 5 10

Correlation CoefficientSlope dO3/dT

-1 -.5 0 .5 1

SE NE

O3 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]

280 300 320 280 300 320

280 300 320 T max [K]

280 300 320 T max [K]

150

100

50

0

150

100

50

0

150

100

50

0

MD

A8

[ppb

]

150

100

50

0

O3 and Temperature Simulated by GCAP

280 300 320

150

100

50

0

MD

A8

[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

MD

A8

[ppb

]

NE has stronger O3/T correlation than SE - GCAP O3/T correlations are slightly stronger in both NE and SE than

observed O3/T correlations

The GCAP results do not vary too much year-to-year

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 O3 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

GCAP Captures the Variation in dO3/dT SlopeSlope of dO3/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 O3 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

[Short-term work]・ Explore reasons for the differences in O3-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

GCAP Phase 2 Science Team meetingat Maxwell Dworkin 223

GCAP Phase 2 Science Team meetingat Maxwell Dworkin 223

GCAP Phase 2 Science Team meetingat Maxwell Dworkin 223

GCAP Phase 2 Science Team meetingat Maxwell Dworkin 223