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DTSTAMP:20190719T085744Z
LOCATION:HG D 1.1
DTSTART;TZID=Europe/Stockholm:20190613T121500
DTEND;TZID=Europe/Stockholm:20190613T124500
UID:submissions.pasc-conference.org_PASC19_sess125_msa125@linklings.com
SUMMARY:Elliptic Solvers for Large-Time-Step Simulations of All-Scale Glob
 al Atmospheric Dynamics
DESCRIPTION:Minisymposium\nComputer Science and Applied Mathematics, Clima
 te and Weather\n\nElliptic Solvers for Large-Time-Step Simulations of All-
 Scale Global Atmospheric Dynamics\n\nSmolarkiewicz, Kühnlein, Wedi\n\nThis
  talk outlines the numerical formulation of the novel non-hydrostatic dyna
 mical core (Finite-Volume Module) of the Integrated Forecasting System (IF
 S) at ECMWF (hereafter IFS-FVM). Its  focus is on the developed semi-
 implicit integrators and the associated elliptic Helmholtz problem. IFS-FV
 M solves perturbation forms of the fully compressible Euler/Navier-Stokes 
 equations under gravity and rotation, using non-oscillatory forward-in-tim
 e semi-implicit time stepping and finite-volume spatial discretisation. Th
 e semi-implicit time stepping is important for circumventing the stability
  restrictions due to all-speed wave motions and for maximising the energet
 ic consistency of numerical integrations. The price to be paid for such ga
 ins is a formidable elliptic Helmholtz problem that imposes an internal en
 ergy constraint on the updated results. The key to solving the resulting l
 inear problem is not a particular linear solver but rather a bespoke desig
 n of the entire IFS-FVM. We start with the governing equations in a form t
 hat facilitates flexible choices for spatial discretisation and time-integ
 ration schemes, then derive an elliptic constraint consistent with the dis
 crete numerics, and end with a bespoke preconditioning of a customised Kry
 lov-subspace solver. Relevant comparisons with spectral-transform based IF
 S-ST attest that IFS-FVM offers highly competitive solution quality and co
 mputational performance; cf. Kühnlein et al. doi:10.5194/gmd-12-651-2
 019.
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