CLaMS (Chemical Lagrangian Model of the Stratosphere) is a modular
chemistry transport model(CTM) system developed at Research Centre Jülich, Germany. CLaMS was first described by McKenna et al (2000a,b) and was expanded into three dimensions by Konopka et al (2004). CLaMS has been employed in recent European field campaigns THESEO, EUPLEX, TROCCINOXand SCOUT-O3with a focus on simulating ozone depletionand water vapourtransport.
Major strengths of CLaMS in comparison to other CTMs are
# its applicability for
reverse domain fillingstudies
# its integrability with arbitrary observational data
# its comprehensive chemistry scheme
Unlike other CTMs (e.g.
SLIMCAT, REPROBUS), CLaMS operates on a Lagrangianmodel grid (see section about model grids in general circulation model): an air parcel is described by three space coordinates and a time coordinate. The time evolutionpath that an air parcels traces in space is called a trajectory. A specialised mixing scheme ensures that physically realistic diffusionis imposed on an ensemble oftrajectories in regions of high wind shear.
CLaMS operates on arbitrarily resolved horizontal grids. The space coordinates are
latitude, longitudeand potential temperature.
CLaMS is composed of four modules and several preprocessors. The four modules are
# a trajectory module
# a box chemistry module
# a Lagrangian mixing module
# a Lagrangian sedimentation scheme
Integration of trajectories with 4th order
Runge-Kutta method, integration time step 30 minutes. Vertical displacement of trajectories is calculated from radiation budget.
Box chemistry module
Chemistry is based on the
ASADchemistry code of the University ofCambridge. More than 100 chemical reactions involving 40+ chemicalspecies are considered. Integration time step is 10 minutes, speciescan be combined into chemical families to facilitate integration. Themodule includes a radiative transfer model for the determination ofphotolysis rates. The module also includes heterogeneous reactions onNAT, ice and liquid particle surfaces.
Mixing is based on grid deformation of quasi uniform air parceldistributions. The contraction or elongation factors of the distancesto neighboring air parcels are examined: if a critical elongation(contraction) is reached, new air parcels are introduced (taken away).This way, anisotropic diffusion is simulated in a physically realisticmanner.
Lagrangian sedimentation is calculated by following individual nitricacid trihydrate (NAT) particles that may grow or shrink by the uptakeor release of HNO3 from/to the gas phase. These particle parcels aresimulated independently from the Lagrangian air parcels. Theirtrajectories are determined using the horizontal winds and theirvertical settling velocity that depends on the size of the individualparticles. NAT particles are nucleated assuming a constant nucleationrate and they evaporate where temperatures grow too high. With this,a vertical redistribution of HNO3 (denitrification andrenitrification) is determined.
CLaMS data sets
chemical transport modeldoes not simulate the dynamics of the atmosphere. For CLaMS, the following meteorological data sets have been used
* European Centre for Medium-Range Weather Forecasts (
ECMWF), Predictions, Analyses, ERA-15, ERA40
* United Kingdom Meteorological Office (
* European Centre Hamburg Atmospheric Model (ECHAM4), in the DLR version
To initialize the chemical fields in CLaMS, data from a large variety of instruments have provided data.
* on satellite (CRISTA, MIPAS, MLS, HALOE, ILAS, ...),
* on aircraft and balloons (HALOX, FISH, Mark IV, BONBON...)
If no observations are present, the chemical fields can be initialisedfrom two-dimensional chemical models,
chemistry-climate models,climatologies, or from correlations between chemical species orchemical species and dynamical variables.
* [http://www.fz-juelich.de/icg/icg-i/clams_e CLaMS at Research Centre Juelich]
* [https://scout-o3.icg.kfa-juelich.de/SCOUT-O3/SCOUT-O3 Current field campaign SCOUT-O3]
The details of the model CLaMS are well documented and published in the scientific literature.
*Formulation of advection and mixing by [http://hdl.handle.net/doi:10.1029/2000JD000114 McKenna et al, 2002a]
*Formulation of chemistry-scheme and initialisation by [http://hdl.handle.net/doi:10.1029/2000JD000113 McKenna et al, 2002b]
*Comparison of the chemistry module with other stratospheric models by [http://hdl.handle.net/doi:10.1023/A:1024056026432 Krämer et al, 2003]
*Calculation of photolysis rates by [http://hdl.handle.net/doi:10.1023/A:1006468926530 Becker et al, 2000]
*Extension to 3-dimension model version by [http://hdl.handle.net/doi:10.1029/2003JD003792 Konopka et al, 2004]
*Lagrangian sedimentation by [http://direct.sref.org/1680-7324/acp/2005-5-1437 Grooß et al, 2005]
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