SMuK 2021 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 1: Oceanography and Climate Modelling
UP 1.3: Vortrag
Donnerstag, 2. September 2021, 11:30–11:45, H3
Horizontal Wave Number Spectra in the Upper Ocean — •Jan Eric Stiehler, Christian Mertens, and Maren Walter — Institut of Environmental Physics, University of Bremen
Even though the spectra of motions in the atmosphere are well known, the same does not hold for the ocean. This has a quite simple reason: velocity measurements in the atmosphere are way more available compared to ocean current measurements as a result of the large amount of airplanes. Resolving temporal and spacial time scales is also easier in the atmosphere due to planes being able to cover much greater areas in the same time compared to ship based measurements. Those motions can be divided into a horizontally rotational part which corresponds to vortex motions in geostrophic balance and a divergent part which resembles internal gravity waves. This is accomplished by calculating and decomposing the spectra of measured shipboard underway ocean current velocity sections and velocity data from a gravity wave resolving ocean general circulation model. The shapes of the resulting model spectra compare well to the observational spectra even though they have approximately an order of magnitude less energy. Both roughly follow a k−3 power law at scales of 50 km to 200 km and k−2 at scales larger than 200 km. The results will also be used to look further into the limits of applicability of this method.