Faculty Candidate Seminar - Thomas Lauvaux

05/14/2018 - 1:00pm
Eckart Lecture Hall room 227
Event Description: 


DATE:          May 14th, Monday, 1p.m.  

LOCATION:     Eckart Lecture Hall
SPEAKER:      Thomas Lauvaux, Ph.D.
            Pennsylvania State University

TITLE:          Atmospheric inversions of greenhouse gases from point sources to ecoregions


As global concentrations of atmospheric greenhouse gases have increased steadily over the last few decades, observation and assimilation systems have emerged as obvious necessities to quantify the role of oceans and continents on the atmospheric composition. While atmospheric greenhouse gas growth rates are observed everywhere around the world, the underlying surface fluxes originate from confined regions of the globe located on land and oceans, from both natural ecosystems and anthropogenic sources. Consequently, assimilation systems reached higher resolutions and observing networks have been densified over urban areas and major ecoregions. 
Atmospheric inversions able to assimilate ground-based, airborne, and spaceborne observations of trace gases are presented in the context of identifying the drivers of recent trends in atmospheric concentrations. Starting with micro-scale inversions capturing site-level emissions, fundamental concepts of the inverse methodology are illustrated with examples of anthropogenic sources modeled with Large Eddy Simulations. Once aggregated over larger urbanized areas, emissions from human activities and man-made landscapes are inferred from mesoscale inversion systems at coarser resolutions. Joint assimilation of multiple trace gases offers additional information on economic sectors of activities, relating surface fluxes to specific processes. The cities of Indianapolis and Los Angeles, where dense observing networks have been deployed, are presented to demonstrate the applicability of the inverse methodology to large metropolitan areas. At larger scales, the inverse problem evolves into high-dimensional optimization systems trying to solve for complex conglomerates of sources and sinks. Most relevant to the inter-annual variability in atmospheric carbon dioxide concentrations, continental carbon budgets require careful consideration of unobserved large-scale inflow, uncertainties in fossil fuel emissions, and complex biogeochemical land and ocean processes. Ensemble-based simulations supported by observations from aircraft campaigns and long-term monitoring networks are presented to better understand and quantify the prevailing sources of errors. The most promising avenues for atmospheric inversions are discussed in the context of climate change and recently observed trends in trace gas concentrations.
 Faculty Host:  Bruce Cornuelle (bcornuelle@ucsd.edu)
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