This talk will report on recent research into the atmospheric flow regime near the transition from storms to hurricanes. This regime is characterized by atmospheric vortices with very strongly tilt that are very far from being small perturbations away from an upright vortex as studied intensively before. Moreover, the decisive structure of a “hurricane eye” and of the associated strong secondary circulation in the “eye wall” is not yet established.
The seminar will begin by summarizing the unified asymptotic framework for atmospheric modelling which this work is built upon. The specification of this framework to the incipient hurricane regime consists of a multi-faceted matched asymptotic expansion in the radial and vertical directions relative to a strongly tilted and time-evolving vortex centreline. The resulting model equations reveal two essentially different mechanisms for the intensification and stabilization of the vortex in the bulk of the troposphere, they explain the control of convection in a vertical layer of intermediate height, and they account for the effects of strong friction in a bottom boundary layer. As an interesting spin-off, this theory has stimulated an extension of the classical quasi-geostrophic/Ekman layer theory for atmospheric flows in the middle latitudes to accommodate an intermediate “diabatic layer” in which the strong influence of moist processes finds an explicit expression.
Results from the asymptotic model compare favourably with full-fledged three-dimensional computational simulations of idealized storms, the latter carried out with a semi-implicit well-balanced scheme for compressible flows. Moreover, advanced techniques of data analysis and visualization help to identify core features predicted by the asymptotics also in computational reconstructions of historical storms.
About the speaker:
Rupert Klein holds a Professorship for Theoretical and Computational Geophysical Fluid Dynamics at the Department of Mathematics and Informatics at Freie Universität Berlin, Germany, where his research group is based.
Rupert holds a diploma in mechanical engineering, with specialization in combustion theory, and obtained a doctoral degree focusing on the computational modelling of knock in internal combustion engines.
He has carried extensive and varied work at Princeton University, RWTH Aachen, Bergische Universität Wuppertal, as well as acting as department head for Data and Computation at the Potsdam Institute for Climate Impact Research (PIK), and as professor of Applied Mathematics/Scientific Computing at the Freie Universität Berlin.
In the course of his research, Rupert has developed and utilized methods of multiscale mathematical modelling and addressed a broad range of applications from combustion, via atmospheric flows and molecular physics to the dynamics of excitons in semi-conducting materials.
Among other honours, Rupert has received the German Leibniz Research Prize of Deutsche Forschungsgemeinschaft (DFG), become a member of the Berlin-Brandenburg Academy of Sciences and been a Fellow of the European Center for Medium Range Weather Forecasts (ECMWF).
Register for this FREE talk here: https://forms.gle/97Wef9kBXBS4CBTu7
This will be a hybrid seminar held at the Maxwell Centre, Cambridge and on Zoom.
Friday 10 June, 3:00 pm – 4:00 pm
JJ Thomson seminar room, Maxwell Centre, JJ Thomson Ave, Cambridge CB3 0HE
Zoom link: https://bit.ly/3OYswjg
Meeting ID: 815 2886 8878 Passcode: 818779 Find your local number: https://us06web.zoom.us/u/kb0WU1V4mi
(Image credit: Oberwolfach Photo Collection)
Friday, 10 June, 2022 – 15:00 to 16:00
Hybrid – Maxwell Centre, Cambridge & on Zoom.