Comparing Models of NOx Chemistry in Asia

Tracey Holloway, Columbia University

MICS-Asia Workshop 2001

Acknowledgements

•Hiram Levy II, NOAA GFDL

•Greg Carmichael, University of Iowa

•Markus Amann and TAP Project, IIASA

•Meredith Galanter, Larry Horowitz, Mahesh Phadnis

•Support from DoD, NASA, Princeton Univ., GFDL

Outline

• Model Overview• Comparing with Observations• Regional Lagrangian vs. Global Eulerian• ATMOS-N Results

ATMOS: Model Overview

• Lagrangian, forward• 1o x 1o resolution• NCEP winds (1990) • NCEP precipitation

• Vertical motion by “puff splitting”

• Linear chemistry only, non-interacting puffs

ATMOS-N Model Chemistry

Fossil Fuel, Biomass Burning, Biogenic

Fossil Fuel Emissions in Asia

kTon NO2/grid-yr (IIASA, Van Ardenne)

Model vs. Observations, I

Observations from Dentener and Crutzen, 1994

Annual Wet HNO3 Deposition (mg N/m2-yr)

Model vs. Observations, II

Annual Wet HNO3 Deposition (mg N/m2-yr)

Observations from Fujita et al., 2000

Model vs. Aircraft Obs

Sept

.-O

ct.

Feb.

-Mar

.

Tropical W. Pac. Mid-lat. W. Pac.

ATMOS

OBS

GFDL GCTM

GCTM: Model Overview

• Global, Eulerian• 11 vertical layers,

variable resolution ~2.5o x 2.5o at mid-latitutes

• GCM-generated winds/precipitation, “typical” year

• Off-line chemistry—same scheme as ATMOS

Deposition Budgets in 2 Models

(kTon N/yr) GCTM,

Asia FF

% Emission ATMOS, Asia FF

% Emission

Fossil Fuel Emissions

6209 4964

Wet HNO3 Dep 3209 52% 1775 36%Dry HNO3 Dep 1220 20% 1298 26%Dry NOx Dep 459 7% 278 6%Dry PAN Dep 146 2% 112 2%Total NOy Dep 5034 81% 3463 70%

GCTM vs. ATMOS-N

Annual Wet HNO3 Deposition (meq/m2-yr)

Global, Eulerian Regional, Lagrangian

ATMOS-N vs. GCTM, at sites

ATMOS

OBS

GFDL GCTMBoth models too low in wet HNO3 deposition, but ATMOS lower.

ATMOS-N vs. GCTM, [HNO3]

Surface

Free Trop.

(~685 mb)

Summary: Model Evaluation

• Overall correct “ballpark” but…

• Wet HNO3 deposition too low vs. obs

• Disagreement greatest at “downwind” sites

• Upper Trop. NOx too low in summer

• Although GCTM is also too low in wet HNO3 deposition, ATMOS-N is lower

• Not enough lateral spreading

• Too much dry deposition

… All trace back to the vertical transport in ATMOS-N…

China Impacts

Winter Summer

% wet HNO3 deposition due to fossil fuel emissions in China relative to all Asia fossil fuel emissions

India Impacts

Winter Summer

Japan Impacts

Winter Summer

Transfer Matrix for HNO3

TAIW JAPAN N KOR S KOR CHINA INDIA

TAIW 80% 2% 2%JAPAN 1% 65% 1% 4%N KOR 3% 34% 7% 1%S KOR 12% 20% 63%CHINA 18% 18% 46% 26% 90%INDIA 1% 6% 95%

FR

OM

…

TO…

Relative Nitrate Burden

Total= Total S + Total NO3

- (meq/m2/yr)

% NO3-

Summary: Regional Transfer of HNO3

• Significant Transfer within east Asia, and from India to west China

• China contributes 18% to total nitrate deposition (wet + dry) in Japan, 46% to North Korea, 26% to South Korea

• Most exchange in winter, when winds are stronger, precipitation less

• NOx much more localized due to shorter lifetime

• Nitrate contributes 30-50% of total acidification over much of Japan, but less than 20% over much of east China.