Publications

Taylor, Mark A.; Strickland, James H.

Abstract not provided.

J. Comput. Phys.

Taylor, Mark A.

Abstract not provided.

Geoscientific Model Development

Guba, Oksana G.; Taylor, Mark A.; Bradley, Andrew M.; Bosler, Peter A.; Steyer, Andrew S.

We present a new evaluation framework for implicit and explicit (IMEX) Runge-Kutta time-stepping schemes. The new framework uses a linearized nonhydrostatic system of normal modes. We utilize the framework to investigate the stability of IMEX methods and their dispersion and dissipation of gravity, Rossby, and acoustic waves. We test the new framework on a variety of IMEX schemes and use it to develop and analyze a set of second-order low-storage IMEX Runge-Kutta methods with a high Courant-Friedrichs-Lewy (CFL) number. We show that the new framework is more selective than the 2-D acoustic system previously used in the literature. Schemes that are stable for the 2-D acoustic system are not stable for the system of normal modes.

Guba, Oksana G.; Taylor, Mark A.; Bradley, Andrew M.; Bosler, Peter A.; Steyer, Andrew S.

Abstract not provided.

Taylor, Mark A.

The diagonal-mass-matrix spectral element method has proven very successful in geophysical applications dominated by wave propagation. For these problems, the ability to run fully explicit time stepping schemes at relatively high order makes the method more competitive then finite element methods which require the inversion of a mass matrix. The method relies on Gauss-Lobatto points to be successful, since the grid points used are required to produce well conditioned polynomial interpolants, and be high quality 'Gauss-like' quadrature points that exactly integrate a space of polynomials of higher dimension than the number of quadrature points. These two requirements have traditionally limited the diagonal-mass-matrix spectral element method to use square or quadrilateral elements, where tensor products of Gauss-Lobatto points can be used. In non-tensor product domains such as the triangle, both optimal interpolation points and Gauss-like quadrature points are difficult to construct and there are few analytic results. To extend the diagonal-mass-matrix spectral element method to (for example) triangular elements, one must find appropriate points numerically. One successful approach has been to perform numerical searches for high quality interpolation points, as measured by the Lebesgue constant (Such as minimum energy electrostatic points and Fekete points). However, these points typically do not have any Gauss-like quadrature properties. In this work, we describe a new numerical method to look for Gauss-like quadrature points in the triangle, based on a previous algorithm for computing Fekete points. Performing a brute force search for such points is extremely difficult. A common strategy to increase the numerical efficiency of these searches is to reduce the number of unknowns by imposing symmetry conditions on the quadrature points. Motivated by spectral element methods, we propose a different way to reduce the number of unknowns: We look for quadrature formula that have the same number of points as the number of basis functions used in the spectral element method's transform algorithm. This is an important requirement if they are to be used in a diagonal-mass-matrix spectral element method. This restriction allows for the construction of cardinal functions (Lagrange interpolating polynomials). The ability to construct cardinal functions leads to a remarkable expression relating the variation in the quadrature weights to the variation in the quadrature points. This relation in turn leads to an analytical expression for the gradient of the quadrature error with respect to the quadrature points. Thus the quadrature weights have been completely removed from the optimization problem, and we can implement an exact steepest descent algorithm for driving the quadrature error to zero. Results from the algorithm will be presented for the triangle and the sphere.

International Conference for High Performance Computing, Networking, Storage and Analysis, SC

Bertagna, Luca B.; Guba, Oksana G.; Taylor, Mark A.; Foucar, James G.; Larkin, Jeff; Bradley, Andrew M.; Rajamanickam, Sivasankaran R.; Salinger, Andrew G.

We present an effort to port the nonhydrostatic atmosphere dynamical core of the Energy Exascale Earth System Model (E3SM) to efficiently run on a variety of architectures, including conventional CPU, many-core CPU, and GPU. We specifically target cloud-resolving resolutions of 3 km and 1 km. To express on-node parallelism we use the C++ library Kokkos, which allows us to achieve a performance portable code in a largely architecture-independent way. Our C++ implementation is at least as fast as the original Fortran implementation on IBM Power9 and Intel Knights Landing processors, proving that the code refactor did not compromise the efficiency on CPU architectures. On the other hand, when using the GPUs, our implementation is able to achieve 0.97 Simulated Years Per Day, running on the full Summit supercomputer. To the best of our knowledge, this is the most achieved to date by any global atmosphere dynamical core running at such resolutions.

Bertagna, Luca B.; Guba, Oksana G.; Taylor, Mark A.; Foucar, James G.; Larkin, Jeff L.; Bradley, Andrew M.; Rajamanickam, Sivasankaran R.; Salinger, Andrew G.

Abstract not provided.

Taylor, Mark A.; Overfelt, James R.; Levy, Michael N.

Abstract not provided.

Mon. Weather Review

Taylor, Mark A.

Abstract not provided.

Guba, Oksana G.; Overfelt, James R.; Taylor, Mark A.

Abstract not provided.

Bosler, Peter A.; Bradley, Andrew M.; Guba, Oksana G.; Taylor, Mark A.

Abstract not provided.

Journal of Advances in Modeling Earth Systems

Taylor, Mark A.; Guba, Oksana G.; Steyer, Andrew S.; Ullrich, Paul A.; Hall, David M.; Eldred, Christopher

We derive a formulation of the nonhydrostatic equations in spherical geometry with a Lorenz staggered vertical discretization. The combination conserves a discrete energy in exact time integration when coupled with a mimetic horizontal discretization. The formulation is a version of Dubos and Tort (2014, https://doi.org/10.1175/MWR-D-14-00069.1) rewritten in terms of primitive variables. It is valid for terrain following mass or height coordinates and for both Eulerian or vertically Lagrangian discretizations. The discretization relies on an extension to Simmons and Burridge (1981, https://doi.org/10.1175/1520-0493(1981)109<0758:AEAAMC>2.0.CO;2) vertical differencing, which we show obeys a discrete derivative product rule. This product rule allows us to simplify the treatment of the vertical transport terms. Energy conservation is obtained via a term-by-term balance in the kinetic, internal, and potential energy budgets, ensuring an energy-consistent discretization up to time truncation error with no spurious sources of energy. We demonstrate convergence with respect to time truncation error in a spectral element code with a horizontal explicit vertically implicit implicit-explicit time stepping algorithm.

Roesler, Erika L.; Taylor, Mark A.; Boslough, Mark B.; Bosler, Peter A.

Abstract not provided.

Backus, George A.; Trucano, Timothy G.; Robinson, David G.; Adams, Brian M.; Richards, Elizabeth H.; Siirola, John D.; Boslough, Mark B.; Taylor, Mark A.; Conrad, Stephen H.; Kelic, Andjelka; Roach, Jesse D.; Warren, Drake E.; Ballantine, Marissa D.; Stubblefield, W.A.; Snyder, Lillian A.; Finley, Ray E.; Horschel, Daniel S.; Ehlen, Mark E.; Klise, Geoffrey T.; Malczynski, Leonard A.; Stamber, Kevin L.; Tidwell, Vincent C.; Vargas, Vanessa N.; Zagonel, Aldo A.

Abstract not provided.

J. Comput. Appl. Math.

Taylor, Mark A.

Abstract not provided.

Michelsen, Hope A.; Bambha, Ray B.; Liu, Zhen L.; Schrader, Paul E.; Ivey, Mark D.; Roesler, Erika L.; Taylor, Mark A.; LaFranchi, Brian L.; Helsel, Frederick M.; Najm, H.N.; Sargsyan, Khachik S.; Safta, Cosmin S.

Abstract not provided.

Int. J. High Performance Computing and applications.

Taylor, Mark A.; Guba, Oksana G.

Abstract not provided.

Taylor, Mark A.

Abstract not provided.

Boslough, Mark B.; Sprigg, James A.; Backus, George A.; Taylor, Mark A.; McNamara, Laura A.; Murphy, Kathryn M.; Malczynski, Leonard A.

This white paper represents a summary of work intended to lay the foundation for development of a climatological/agent model of climate-induced conflict. The paper combines several loosely-coupled efforts and is the final report for a four-month late-start Laboratory Directed Research and Development (LDRD) project funded by the Advanced Concepts Group (ACG). The project involved contributions by many participants having diverse areas of expertise, with the common goal of learning how to tie together the physical and human causes and consequences of climate change. We performed a review of relevant literature on conflict arising from environmental scarcity. Rather than simply reviewing the previous work, we actively collected data from the referenced sources, reproduced some of the work, and explored alternative models. We used the unfolding crisis in Darfur (western Sudan) as a case study of conflict related to or triggered by climate change, and as an exercise for developing a preliminary concept map. We also outlined a plan for implementing agents in a climate model and defined a logical progression toward the ultimate goal of running both types of models simultaneously in a two-way feedback mode, where the behavior of agents influences the climate and climate change affects the agents. Finally, we offer some ''lessons learned'' in attempting to keep a diverse and geographically dispersed group working together by using Web-based collaborative tools.

Taylor, Mark A.

Abstract not provided.

Taylor, Mark A.

Abstract not provided.

Taylor, Mark A.

Abstract not provided.

Taylor, Mark A.

Abstract not provided.

SIAM Journal on Scientific Computing

Bradley, Andrew M.; Bosler, Peter A.; Guba, Oksana G.; Taylor, Mark A.; Barnett, Gregory A.

Atmospheric tracer transport is a computationally demanding component of the atmospheric dynamical core of weather and climate simulations. Simulations typically have tens to hundreds of tracers. A tracer field is required to preserve several properties, including mass, shape, and tracer consistency. To improve computational efficiency, it is common to apply different spatial and temporal discretizations to the tracer transport equations than to the dynamical equations. Using different discretizations increases the difficulty of preserving properties. This paper provides a unified framework to analyze the property preservation problem and classes of algorithms to solve it. We examine the primary problem and a safety problem; describe three classes of algorithms to solve these; introduce new algorithms in two of these classes; make connections among the algorithms; analyze each algorithm in terms of correctness, bound on its solution magnitude, and its communication efficiency; and study numerical results. A new algorithm, QLT, has the smallest communication volume, and in an important case it redistributes mass approximately locally. These algorithms are only very loosely coupled to the underlying discretizations of the dynamical and tracer transport equations and thus are broadly and efficiently applicable. In addition, they may be applied to remap problems in applications other than tracer transport.

Bosler, Peter A.; Guba, Oksana G.; Taylor, Mark A.; Bradley, Andrew M.; nadiga, balu n.; Sun, Xiaoming S.; maltrud, mat m.

Abstract not provided.