Master defence by Thomas Bjerring Kristensen, Department of Geophysics – Niels Bohr Institute - University of Copenhagen

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Niels Bohr Institute > Calendar > 2008 > Master defence by Thom...

Master defence by Thomas Bjerring Kristensen, Department of Geophysics

Title: Particle Fluxes

Climate change observed through the recent decades has drawn attention to the need of a better understanding of the mechanisms influencing climate. Aerosol particles are currently considered one of the greatest “unknowns” when it comes to a better understanding of climate.

An increased concentration of aerosol particles tend to cool climate directly by scattering of  incoming short wave radiation. The aerosol particle concentration also affect climate indirectly by modification of optical properties and lifetimes of clouds. Both when it comes to the magnitude of the sources and the impacts of different aerosol particles - an increased understanding is needed.

The oceans are the greatest source of natural aerosol particles. However measurements of particle fluxes over the oceans are very scarce - and it’s is hard to derive eddy covariance (EC) fluxes from moving platforms such as ships. Two other methods to infer particle fluxes – the inertial dissipation method (IDM) and the cospectral method (CSM) - are introduced and tested for the first time on a large dataset. Both new methods produce promising results when tested vs the EC on land based measurements above a forest.

Marine aerosol particle fluxes are inferred from measurements on the Galathea 3 and the Marine Aerosol Particle cruises applying the IDM. The IDM and the CSM are not as sensitive to ship-motion and flow-distortion as the EC. When it comes to seasalt-fluxes the results are in line with other reported observations and parameterizations. However when it comes to total particle fluxes the Atlantic seems to be a significant source of volatile aerosol particles. It should be possible to conduct ship-based measurements with a favorable experimental setup to infer much more reliable particle fluxes using the IDM and the CSM together.

Time: November 10, 2 pm
Place: Rockefeller – Auditoriet, Juliane Maries Vej 30

Aksel Walløe Hansen, GFY
Merete Bilde, KIKU
Lise Lotte Sørensen, DMU