TY - GEN

T1 - Solving vertical transport and chemistry in air pollution models

AU - Berkvens, P.J.F.

AU - Bochev, M.A.

AU - Krol, M.C.

AU - Peters, W.

AU - Verwer, J.G.

N1 - Please note different possible spellings of the second author's name: "Botchev" or "Bochev"

PY - 2002

Y1 - 2002

N2 - For the time integration of stiff transport-chemistry problems from air pollution modelling, standard ODE solvers are not feasible due to the large number of species and the 3D nature. The popular alternative, standard operator splitting, introduces artificial transients for short-lived species. This complicates the chemistry solution, easily causing large errors for such species. In the framework of an operational global air pollution model, we focus on the problem formed by chemistry and vertical transport, which is based on diffusion, cloud-related vertical winds, and wet deposition. Its specific nature leads to full Jacobian matrices, ruling out standard implicit integration.
We compare Strang operator splitting with two alternatives: source splitting and an (unsplit) Rosenbrock method with approximate matrix factorization, all having equal computational cost. The comparison is performed with real data. All methods are applied with half-hour time steps, and give good accuracies. Rosenbrock is the most accurate, and source splitting is more accurate than Strang splitting. Splitting errors concentrate in short-lived species sensitive to solar radiation and species with strong emissions and depositions.

AB - For the time integration of stiff transport-chemistry problems from air pollution modelling, standard ODE solvers are not feasible due to the large number of species and the 3D nature. The popular alternative, standard operator splitting, introduces artificial transients for short-lived species. This complicates the chemistry solution, easily causing large errors for such species. In the framework of an operational global air pollution model, we focus on the problem formed by chemistry and vertical transport, which is based on diffusion, cloud-related vertical winds, and wet deposition. Its specific nature leads to full Jacobian matrices, ruling out standard implicit integration.
We compare Strang operator splitting with two alternatives: source splitting and an (unsplit) Rosenbrock method with approximate matrix factorization, all having equal computational cost. The comparison is performed with real data. All methods are applied with half-hour time steps, and give good accuracies. Rosenbrock is the most accurate, and source splitting is more accurate than Strang splitting. Splitting errors concentrate in short-lived species sensitive to solar radiation and species with strong emissions and depositions.

KW - MSC-65Y20

KW - EWI-8854

KW - IR-66799

KW - MSC-65M20

KW - MSC-65M06

M3 - Conference contribution

SN - 9780387954974

T3 - IMA Volumes in Mathematics and its Applications

SP - 1

EP - 20

BT - Atmospheric Modeling

A2 - Chock, David P.

A2 - Carmichael, Gregory R.

A2 - Brick, Patricia

PB - Springer

T2 - IMA Atmospheric Modeling Workshop 2000

Y2 - 15 March 2000 through 19 March 2000

ER -