Forschung und wissenschaftliches Rechnen - Beiträge zum - GWDG

automatic time step control. Although computationally more demanding, the
latter are best suited for the most difficult stiffness problems e.g. associated
with multiphase chemistry. For each individual application, it is necessary to
balance the advantages and disadvantages regarding efficiency, stability, accuracy,
and precision. We found that for most of our chemical mechanisms,
the Rosenbrock solvers of 2nd or 3rd order (ros2 and ros3) work best. However,
we stress that it may be necessary to test other solvers as well (e.g.
radau5) to achieve the best performance for a given set of equations. Fortunately,
switching between solvers is easy with KPP and does not require
any reprogramming of the chemistry scheme. The selection of a chemical
equation set and a numerical solver is shown in Fig. 6.
4.16 OFFLEM
MAINTAINER: Patrick Jöckel
DESCRIPTION: This submodel reads input data from files for two-dimensional
emission fluxes (i.e. surface emissions in molecules/(m 2 s)) and threedimensional
emission fluxes (aircraft emissions in molecules/(m 3 s)) and updates
the tracer tendencies (gridpoint- and Lagrangian) accordingly.
4.17 ONLEM
MAINTAINER: Astrid Kerkweg
CONTRIBUTIONS: Yves Balkanski (LSCE), Ina Tegen (MPI-BG), Philip
Stier (MPI-MET), Sylvia Kloster (MPI-MET), Laurens Ganzeveld, Michael
Schulz (LSCE)
DESCRIPTION: This submodel calculates two-dimensional emission fluxes
for gas-phase tracers (i.e. surface emissions in molecules/(m 2 s)) and updates
the tracer tendencies accordingly. In addition, aerosol source functions are
calculated.
4.18 PSC
MAINTAINER: Joachim Buchholz
ORIGINAL CODE: Ken Carslaw, Stefanie Meilinger, Joachim Buchholz
DESCRIPTION: The Polar Stratospheric Cloud (PSC) submodel simulates
micro-physical processes that lead to the formation of super-cooled ternary
solutions (STS), nitric acid trihydrate (NAT), and ice particles in the polar
stratosphere as well as heterogeneous chemical reactions of halogens and
dinitrogen pentoxide on liquid and solid aerosol particles. Denitrification and
dehydration due to sedimenting solid PSC particles are calculated for each
grid box depending on particle size, pressure and temperature.
25