Lin Zhang

Harvard Univeristy

Research Overview

I am now a research associate with Prof. Daniel J. Jacob at Harvard Atmospheric Chemistry Modeling group. My current research focuses on understanding contributions of human and natural sources to nitrogen deposition in the United States. My PhD research has used new capabilities of satellite measurements and the adjoint inverse modeling to improve our knowledge on intercontinental transport of ozone pollution.

More generally, my research interests are to understand changes of atmospheric composition (air pollutants and greenhouse gases) due to human and natural activities, and their implications on environment and climate change.


  • Nitrogen Deposition over the United States
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  • North American Background Ozone over the United States
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  • Tropospheric Ozone Measurements from TES and OMI
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  • Adjoint Analysis of Ozone Source Attribution
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  • Intercontinental Transport of Ozone Pollution
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  • Tropospheric Ozone and CO Measurements from Space
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    Nitrogen Deposition over the United States

    Source Attribution of Nitrogen Deposition Over the United States


    Atmospheric inputs of reactive nitrogen (fixed nitrogen) to ecosystems have increased by more than a factor of 3 globally due to human activity, significantly perturbing the global nitrogen cycle. The US Environmental Protection Agency (EPA) is presently developing secondary air quality standards for protection of ecosystems against the detrimental effects of nitrogen deposition. This requires a better understanding of nitrogen deposition over the US in its various forms and including contributions from sources both natural and anthropogenic, foreign and domestic. We use here a nested version of the global GEOS-Chem chemical transport model (CTM) to address these issues.
    Figure above shows domestic anthropogenic, foreign anthropogenic, and natural contributions to annual nitrogen deposition over the US as computed by GEOS-Chem for 2006.

    The project is funded by the Electric Power Research Institute (EPRI)

    For more information:

    • Zhang, L., D.J. Jacob, E.M. Knipping, N. Kumar, J.W. Munger, C.C. Carouge, A. van Donkelaar, Y. Wang, and D. Chen, Nitrogen deposition to the United States: distribution, sources, and processes, submitted to Atmos. Chem. Phys.,, 2011. [pdf]

    North American Background Ozone over the United States

    Improved estimate of the policy-relevant background ozone in the United States

    The policy-relevant background (PRB) ozone is defined by the US Environmental Protection Agency (EPA) as the surface ozone concentration that would be present over the US in the absence of North American anthropogenic emissions. It is intended to provide a baseline for risk and exposure assessments used in setting the National Ambient Air Quality Standard (NAAQS).

    We used the GEOS-Chem global 3-D model of atmospheric composition with 1/2° × 2/3° horizontal resolution over North America and adjacent oceans (2° × 2.5° for the rest of the world) to estimate three-year statistics (2006-2008) of PRB ozone over the US.

    Figure above shows the 4th-highest value of North American background ozone (PRB) calculated in GEOS-Chem as daily 8-hr maximum ozone and averaged for 2006-2008. We are now investigating the influences of stratospheric intrusions, lightning, and wildfires on the surface ozone air quality over the intermountain west US.

    The project is funded by BP America.

    For more information:

    • Zhang, L., D.J. Jacob, N.V. Smith-Downey, D.A. Wood, D. Blewitt, C.C. Carouge, A. van Donkelaar, D.B.A. Jones, L.T. Murray, and Y. Wang, Improved estimate of the policy-relevant background ozone in the United States using the GEOS-Chem global model with 1/2ox2/3o horizontal resolution over North America, Atmos. Environ., 45, 6769-6776, 2011. [pdf]