GEOS-CHEM Activities at NIA

Hongyu Liu

​

National Institute of Aerospace (NIA)

at NASA LaRC

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​

June 2, 2003

²¹⁰Pb-⁷Be-O₃ relationships

²¹⁰Pb-⁷Be-O₃ relationships during PEM-West A (Sept-Oct 1991)

Near Asia

Remote Pacific

Remote Pacific

Near Asia

²¹⁰Pb-O₃

⁷Be-O₃

UT

MT

LT

OBSERVATION vs. MODEL

²¹⁰Pb-⁷Be-O₃ relationships during PEM-West B

²¹⁰Pb-O₃

⁷Be-O₃

UT

LT

MT

OBSERVATION vs. MODEL

Near Asia

Remote Pacific

Near Asia

Remote Pacific

²¹⁰Pb-⁷Be-O₃ relationships during TRACE-P

< 30^oN

> 30^oN

< 30^oN

> 30^oN

²¹⁰Pb-O₃

⁷Be-O₃

UT

LT

MT

OBSERVATION vs. MODEL

• RAQMS (regional) & GEOS-CHEM (global);
• LaRC/UW Regional Air Quality Modeling System

(RAQMS) jointly developed by NASA Langley and Univ

Wisconsin [Pierce et al., 2003];

• Fast-J2 scheme recently implemented in RAQMS
• Cloud and trace gas distributions
• Cloud optical depth (model vs. satellite)
• ……

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The effect of clouds on Asian pollution outflow

during TRACE-P

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(with Brad Pierce, Jim Crawford, et al.)

Intercontinental transport, Continental outflow, and Chemical processing of aerosols with GEOS-CHEM

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Duncan Fairlie*

Rokjin Park

Daniel Jacob

​

Dept. Earth and Planetary Sciences

Harvard University

*Also NASA Langley Research Center, Hampton, VA

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2 June 2003

Project Goals:

1. Assess the impact of intercontinental transport of mineral dust on aerosol concentrations in North America

(2) Assess the global impact of heterogeneous uptake on mineral dust on SO₄⁼ production and NO_y partitioning

(3) Quantify export of aerosols and precursors from the North America, and relate to sources.

Aerosol Module in GEOS-CHEM

Aerosol Module: Based on GOCART (Chin et al., 2002):

SO₄, sea salt, dust, OC, EC.

• Added NH₃ (Adams et al., 1999), H₂SO₄-HNO₃-NH₃-H₂O thermodynamics (Nenes et al., 1998). Rokjin Park

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• Dust module:
• Mobilization: Ginoux et al. (2001)
• Dry deposition: Zhang et al. (2000)
• Wet deposition: Liu et al. (2001)
• Dust size bins: 0.1-1.0, 1.0-1.8, 1.8-3.0, 3.0-6.0 μm

radius.

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Full coupling with oxidant-aerosol chemistry: gas-aqueous sulfur oxidation; HNO₃/nitrate partitioning; heterogeneous uptake of N₂O₅, NO₂, NO₃, HO₂; impact on photolysis rates.

1. How much does Asian dust contribute to concentrations over North America?

• Use GEOS-CHEM to quantify intercontinental transport

of dust to the U.S.

• Evaluate the model with data from the IMPROVE network, AERONET observations, TRACE-P and ACE-Asia data, and MODIS AOD.
• Assess the model against the constraints of observations.

Simulated dust

April, 2001

2001 annual dust simulation

Total Emission: 2500Tg/yr

DRYD: 1400Tg/yr

WETD: 1100Tg/yr

Avg. Burden: 37Tg

200

500

50

2000

mg/m²

Tons/km²/yr

Tons/km²/yr

Tons/km²/yr

IMPROVE sites: extreme Asian dust event in April 2001

0

4

8 μg/m³

16 April, 2001

22 April 2001

IMPROVE

Dust PM2.5

Discrepancies between model and data suggest local sources too strong

IMPROVE

PM2.5 dust

MODEL

w/ all sources

Model

w/o NA

sources

18 west

sites

12 east

sites

April 2001

2. Evaluate global impact of uptake of SO₄⁼ and NO₃^- on dust

• GEOS-CHEM - fully coupled aerosol-gas simulation.
• Uptake of HNO₃, SO₂, H₂SO₄ on dust.
• Carry alkalinity as a tracer to limit uptake
• Distinguish alkalinity differences at source.
• Use obs. to assess simulation, and constrain sources.

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TRACE-P

ACE-Asia

3. Impact of continental outflow on the global atmosphere:

Key science objective of INTEX:

• What is the aerosol outflow from N. America, and how does it relate to surface sources?
• What are the outflow mechanisms, and how do they differ for aerosols, gases?

INTEX

Mission

2004

The role of dust: Navajo Mountain, Page, AZ �typical view 16 April 2001

EPA regional haze rule:

“return Federal

Class I regions to natural

visibility conditions by 2064.”

Dust arrives

behind cold

front

SeaWifs

11 April

Chemical modification due to uptake of HNO₃, SO₂, H₂SO₄ on mineral dust

• Change global NO_x/HNO₃ partitioning.

and impact O₃ budget.

• Speed up SO₂ conversion to sulfate, and impact the SO₄⁼ lifetime.
• Make dust hygroscopic and promote additional aqueous surface reactions, e.g. SO₂, N₂O₅
• Shift aerosol sizes to larger particles. Impact radiative properties.