Emissions from China: Implications for the Regional and

Global Environment

Yuxuan WangYuxuan Wang

Advisor: Michael McElroyAdvisor: Michael McElroy

Ph.D. Thesis DefensePh.D. Thesis Defense

January. 21, 2005January. 21, 2005

[Introduction to atmospheric chemistry, Daniel Jacob, 1999]

Surface Air Quality is not just a Regional Issue

“Optimistic” IPCC scenario: Asia UP by 50%; EU, U.S. down by 20%

Uncertainty in the Bottom-up Emissions

Coal Consumption for China

0

200

400

600

800

1000

1200

Year

Mill

ion

ton

sce

total coal consumption

coal for power generation

Bottom-up emissions ~ ( activity rate * emission factor)

Uncertainty in the Bottom-up Emissions

Coal Consumption for China

0

200

400

600

800

1000

1200

Year

Mill

ion

ton

sce

total coal consumption

coal for power generation

Bottom-up emissions ~ ( activity rate * emission factor)

?

Circulation Patterns and Implications for Air Quality

Winter Monsoon Conditions Summer Monsoon Conditions

Depending on different time of the year, air quality over Hong Kong is subject to influences from Chinese mainland, Northeast Asia and Southeast Asia.

My Thesis Research

1.1. Development of a nested grid Development of a nested grid capacity in GEOS-CHEM modelcapacity in GEOS-CHEM model

2.2. Forward model analysis of aircraft Forward model analysis of aircraft and surface measurements of CO and surface measurements of CO and NOand NOyy

3.3. Inverse model analysis to constrain Inverse model analysis to constrain Chinese emissions of CO and NOChinese emissions of CO and NOxx

4.4. Food chain related emissions of Food chain related emissions of NN22O and NOO and NOxx

GEOS-CHEM Global 3-D Model

Resolution: 4Resolution: 4 x5 x5 or or 22 x2.5 x2.5 Driven by assimilated meteorological fieldsDriven by assimilated meteorological fields Coupled gas phase and aerosol simulationsCoupled gas phase and aerosol simulations

Nested Grid Version of GEOS-CHEM

11 x1 x1

44 x5 x5

Heterogeneous Emission Patterns and Topography

CO Emissions over Southern China

Terrain Elevations

Aircraft and Chinese Stations Data

Time frame: Jan – Apr., 2001

Nested-grid model provides good agreement with observations

Model Underestimates Aircraft Observations of CO and NOy

Model Underestimates Surface Measurements

CO

NOy

A priori Emissions of CO and NOx

r

Uncertainties: 154% for CO, 27% for NOx

Source: Streets et al. [2003]

Forward Model Analysis

Emissions

Observations

GEOS-CHEM

Forward

Inverse Model Analysis

Emissions

Observations

GEOS-CHEMInverse

Forward

Tagged Tracer Simulation

Monitoring site measures concentration C

Atmospheric “forward” model gives C = kE

NOy Chemistry and Deposition Scheme

1. Model has no bias in simulating 1. Model has no bias in simulating contributions of contributions of component NOcomponent NOyy species to total NO species to total NOyy below 6km below 6km

no systematic bias in NOno systematic bias in NOyy chemistry and relative chemistry and relative deposition rate in the model deposition rate in the model

2. Linear relationship between NO2. Linear relationship between NOxx emissions and NO emissions and NOyy concentrations can thus be adopted. concentrations can thus be adopted.

Inverse modeling• Bayesian approach to linear inversion with Gaussian

statistics [Palmer et al., 2003]

a posteriori state vector

a posteriori error covariance matrix

The inversion is conducted independently for CO and NOy

Both aircraft (spatial coverage) and station data (temporal coverage) are used in the inverse analysis

The inverse model is not designed to constrain sinks of CO and NOy

)Kx(ySK)SKS(Kxx a1

ΣT11

a1

ΣT

a

11a

1Σ

T )SKS(KS

)x(xS)x(xKx)(ySKx)(y(x) a1

aT

a1

ΣT J

CO

NOx

A posteriori Emissions Significantly Reduce Model Bias

A posteriori Emissions Significantly Reduce Model Bias

A posteriori Emissions Significantly Reduce Model Bias

Revising the ‘Bottom-up’ CO Emissions : Low Efficiency Industrial Processes

courtesy of Q. Zhang

+34% higher (73% from +34% higher (73% from

industrial sector)industrial sector)

?

Microbial Sources of N2O and NOx

Nitrification: NHNitrification: NH44++ NO NO22

-- NO NO33--

Denitrification: NODenitrification: NO33-- N N22O O N N22

The weight of the evidence suggests The weight of the evidence suggests that nitrification provides the that nitrification provides the dominant source of Ndominant source of N22O. O.

NH2OH

N2O, NO

O2 O2

Microbial Sources of N2O and NOx

Nitrification: NHNitrification: NH44++ NO NO22

-- NO NO33--

Denitrification: NODenitrification: NO33-- N N22O O N N22

The weight of the evidence suggests The weight of the evidence suggests that nitrification provides the that nitrification provides the dominant source of Ndominant source of N22O. O.

NH2OH

N2O, NO

O2 O2

N2O, NO

Low levels of O2 Aerobic denitr.

Survey of Field and Laboratory Studies

Yield of NYield of N22O and NO increases with O and NO increases with

decreasing levels of Odecreasing levels of O22

So does the NO / NSo does the NO / N22O ratio O ratio

Top-down Budget of N2O

1.1. Sink: photolytic process in the Sink: photolytic process in the stratosphere stratosphere lifetime 120 yr lifetime 120 yr

2.2. Pre-industrial concentration: 270 ppb Pre-industrial concentration: 270 ppb natural source of 10.9 TgN/yr natural source of 10.9 TgN/yr

3.3. Current concentration (314ppb) and Current concentration (314ppb) and annual increase rate (0.8ppb) annual increase rate (0.8ppb) current source of 16.6 TgN/yrcurrent source of 16.6 TgN/yr

4.4. Anthropogenic source: 5.7 TgN/yrAnthropogenic source: 5.7 TgN/yr Fossil fuel and industrial processes: Fossil fuel and industrial processes:

1.3 TgN/yr1.3 TgN/yr Microbial sources: Microbial sources: 4.4 4.4 TgN/yr TgN/yr

N Processed through the Agriculture/Animal/Human Food Chain

0

50

100

150

200

250

Tg

N/y

r

Global China India US EU Russia

animal wastes

human wastes

chemical fertilizer

226

N Processed through the Agriculture/Animal/Human Food Chain

226 TgN/yr * 2% = 4.4 TgN-N2O /yr

NOx/N2O = 3 or 6% yield for NOx

0

50

100

150

200

250

Tg

N/y

r

Global China India US EU Russia

animal wastes

human wastes

chemical fertilizer

Central China: 30% of Chinese N 0.9 TgN-NOx/yr

226

N Processed by Domestic Animals

0

5

10

15

20

25

Tg

N/y

r

China India US EU

others

poultry

sheeppigs

cattle

Trends in N Processed through the Global Food Chain

Use the yield of 2% for N2O

Trends in Atmospheric N2O using a One-box Model

dC / dt = S / 4.8 – C/τ

Summary

1.1. The nested grid model provides an The nested grid model provides an adequate account of the adequate account of the meteorological features in spring time meteorological features in spring time over China over China [[Wang et al.,Wang et al., JGR, 2004a JGR, 2004a]]

2.2. The current inventory underestimated The current inventory underestimated Chinese emissions of CO and NOChinese emissions of CO and NOx x

[[Wang et al.,Wang et al., JGR, 2004b JGR, 2004b]]

3.3. Biological emissions of NBiological emissions of N22O and NOO and NOxx are significant for large developing are significant for large developing countries countries [[McElroy andMcElroy and Wang,Wang, GBC, 2005 GBC, 2005]]

Acknowledgement

• Michael McElroyMichael McElroy• Daniel JacobDaniel Jacob• Steve Wofsy, Dan SchragSteve Wofsy, Dan Schrag• Jennifer Logan, Chris Nielsen, Tao Wang, Jennifer Logan, Chris Nielsen, Tao Wang,

Paul PalmerPaul Palmer• Atmospheric chemistry modeling groupAtmospheric chemistry modeling group• HUCE China ProjectHUCE China Project• EPS departmentEPS department• My familyMy family