Semi-implicit time-integrators for a scalable spectral element atmospheric model
نویسنده
چکیده
The Naval Research Laboratory’s spectral element atmospheric model (NSEAM) for scalable computer architectures is presented. This new dynamical core is based on a high-order spectral element (SE) method in space and uses semi-implicit methods in time based on either the traditional second-order leapfrog (LF2) or second-order backward difference formulas (BDF2). The novelties of NSEAM are: it is geometrically flexible and thereby can accommodate any type of grid; LF2 or BDF2 are used to construct the semi-implicit method; and the horizontal operators are written, discretized, and solved in three-dimensional Cartesian space. The semi-implicit NSEAM is validated using: five baroclinic test cases; direct comparisons to the explicit version of NSEAM which has been extensively tested and the results previously reported in the literature; and comparisons with operational weather prediction and well-established climate models. A comparison with the US Navy’s spectral transform global forecast model illustrates that NSEAM is 60% faster on an IBM SP4 using 96 processors for the current operational resolution of T239 L30. However, NSEAM can accommodate many more processors while continuing to scale efficiently even at higher grid resolutions. In fact, we show that at T498 L60, NSEAM scales linearly up to 384 processors.
منابع مشابه
Semi-Implicit Formulations of the Navier--Stokes Equations: Application to Nonhydrostatic Atmospheric Modeling
We present semi-implicit (IMEX) formulations of the compressible Navier-Stokes equations (NSE) for applications in nonhydrostatic atmospheric modeling. The compressible NSE in nonhydrostatic atmospheric modeling include buoyancy terms that require special handling if one wishes to extract the Schur complement form of the linear implicit problem. We present results for five different forms of th...
متن کاملRecent Progress in Nonlinear and Linear Solvers
We discuss two approaches for tackling algebraic systems; one is based on block preconditioning, and the other is based on multifrontal and hierarchical matrix methods. First we consider a new preconditioner framework for supporting implicit time integration within an atmospheric climate model. We give an overview of the computational infrastructure used in atmospheric climate studies, address ...
متن کاملTwo conservative multi-tracer efficient semi-Lagrangian schemes for multiple processor systems integrated in a spectral element (climate) dynamical core
In today’s atmospheric numerical modeling, scalable and highly accurate numerical schemes are of particular interest. To address these issues Galerkin schemes, such as the spectral element method, have received more attention in the last decade. They also provide other state-of-the-art capabilities such as improved conservation. However, the tracer transport of hundreds of tracers, e.g., in the...
متن کاملSemi-lagrangian Transport Algorithms for the Shallow Water Equations in Spherical Geometry
Global atmospheric circulation models (GCM) typically have three primary algorithmic components: columnar physics, spectral tran-form, and semi-Lagrangian transport. In this study, several varients of a SLT method are studied in the context of test cases for the shallow water equations in spherical geometry. A grid point formulation is used with implicit, semi-implicit or explicit time integrat...
متن کامل