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Friday, March 6, 2020 - 12:00pm to 1:00pm
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100F Pierce Hall, 29 Oxford St., Cambridge

Atmospheric & Environmental Chemistry Seminar

"Satellite-based Constraints on Aerosol, Aerosol Precursor, and Greenhouse-gas Emissions: Applications and New Inverse Modeling Techniques" with Daven Henze, University of Colorado Boulder.

In this talk, I will present findings from several recent and current studies applying chemical transport modeling and satellite-based remote sensing to improve our understanding of the origins and fates of atmospheric constituents.  I will present top-down constraints on NH3, an important aerosol precursor, based on 4D-Var inversions using new retrievals from the CrIS instrument aboard the Suomi-NPP satellite. We find that NH3 emission estimates are broadly underestimated, and that CrIS data allows us to improve our model estimates of surface NH3 concentrations and NHx deposition. Time and interest permitting, I may also present top-down analysis of NO2 and NOx emission trends, touching on recent studies in the literature that offer differing explanations for notable discrepancies between trends in NO2 concentrations, surface NO2 measurements, and bottom-up NOx emissions estimates. Lastly, I will discuss some critical challenges in inverse modeling and assimilation techniques commonly used for large-dimensional systems in atmospheric chemistry and meteorology.  In particular, I will discuss methods developed in our group to estimate the uncertainty of 4D-Var inverse modeling estimates, a long-standing challenge with this approach. This encompasses new techniques for optimal dimension reductions of these inherently large-scale inverse problems, using randomization methods and singular value decomposition, which opens up new dimensions for computational parallelization within operational chemical data assimilation and numerical weather prediction systems. 

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Harvard University
Center for the Environment

Address: 26 Oxford Street, 4th Floor, Cambridge
Email: huce@environment.harvard.edu
Phone: (617) 495-0368

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