Advisor: Michael McElroy Emissions from China: Implications for the Regional and Global Environment Yuxuan Wang Advisor: Michael McElroy Ph.D. Thesis Defense January. 21, 2005

Surface Air Quality is not just a Regional Issue “Optimistic” IPCC scenario: Asia UP by 50%; EU, U.S. down by 20% [Introduction to atmospheric chemistry, Daniel Jacob, 1999]

Uncertainty in the Bottom-up Emissions Bottom-up emissions ~ ( activity rate * emission factor)

Uncertainty in the Bottom-up Emissions 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 Development of a nested grid capacity in GEOS-CHEM model Forward model analysis of aircraft and surface measurements of CO and NOy Inverse model analysis to constrain Chinese emissions of CO and NOx Food chain related emissions of N2O and NOx

GEOS-CHEM Global 3-D Model Resolution: 4 x5 or 2 x2.5 Driven by assimilated meteorological fields Coupled gas phase and aerosol simulations

Nested Grid Version of GEOS-CHEM 1 x1 4 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 Uncertainties: 154% for CO, 27% for NOx r Source: Streets et al. [2003]

Forward Model Analysis Observations Emissions GEOS-CHEM

Inverse Model Analysis Forward Observations Inverse Emissions GEOS-CHEM

Tagged Tracer Simulation Atmospheric “forward” model gives C = kE Monitoring site measures concentration C

NOy Chemistry and Deposition Scheme 1. Model has no bias in simulating contributions of component NOy species to total NOy below 6km  no systematic bias in NOy chemistry and relative deposition rate in the model 2. Linear relationship between NOx emissions and NOy 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

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 +34% higher (73% from industrial sector) courtesy of Q. Zhang

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Microbial Sources of N2O and NOx Nitrification: NH4+  NO2-  NO3- Denitrification: NO3-  N2O  N2 The weight of the evidence suggests that nitrification provides the dominant source of N2O. O2 NH2OH N2O, NO

Microbial Sources of N2O and NOx Nitrification: NH4+  NO2-  NO3- Denitrification: NO3-  N2O  N2 The weight of the evidence suggests that nitrification provides the dominant source of N2O. O2 NH2OH Low levels of O2 Aerobic denitr. N2O, NO N2O, NO

Survey of Field and Laboratory Studies Yield of N2O and NO increases with decreasing levels of O2 So does the NO / N2O ratio

Top-down Budget of N2O Sink: photolytic process in the stratosphere  lifetime 120 yr Pre-industrial concentration: 270 ppb  natural source of 10.9 TgN/yr Current concentration (314ppb) and annual increase rate (0.8ppb)  current source of 16.6 TgN/yr Anthropogenic source: 5.7 TgN/yr Fossil fuel and industrial processes: 1.3 TgN/yr Microbial sources: 4.4 TgN/yr

N Processed through the Agriculture/Animal/Human Food Chain 226

N Processed through the Agriculture/Animal/Human Food Chain 226 226 TgN/yr * 2% = 4.4 TgN-N2O /yr NOx/N2O = 3 or 6% yield for NOx Central China: 30% of Chinese N  0.9 TgN-NOx/yr

N Processed by Domestic Animals

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 The nested grid model provides an adequate account of the meteorological features in spring time over China [Wang et al., JGR, 2004a] The current inventory underestimated Chinese emissions of CO and NOx [Wang et al., JGR, 2004b] Biological emissions of N2O and NOx are significant for large developing countries [McElroy and Wang, GBC, 2005]

Acknowledgement Michael McElroy Daniel Jacob Steve Wofsy, Dan Schrag Jennifer Logan, Chris Nielsen, Tao Wang, Paul Palmer Atmospheric chemistry modeling group HUCE China Project EPS department My family