iPedia Free Information Center

Information about Clams

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, TROCCINOX and SCOUT-O3 with a focus on simulating ozone depletion and water vapour transport.

Unlike other CTMs (e.g. SLIMCAT, REPROBUS), CLaMS operates on a Lagrangian model 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 evolution path that an air parcels traces in space is called a trajectory. A specialised mixing scheme ensures that physically realistic diffusion is imposed on an ensemble of trajectories in regions of high wind shear.

CLaMS operates on arbitrarily resolved horizontal grids. The space coordinates are latitude, longitude and potential temperature.

Major strengths of CLaMS in comparison to other CTMs are
  1. its applicability for reverse domain filling studies
  2. its anisotropic mixing scheme
  3. its integrability with arbitrary observational data
  4. its comprehensive chemistry scheme

CLaMS Hierarchy

CLaMS is composed of four modules and several preprocessors. The four modules are
  1. a trajectory module
  2. a box chemistry module
  3. a Lagrangian mixing module
  4. a Lagrangian sedimentation scheme

Trajectory module

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 ASAD chemistry code of the University of Cambridge. More than 100 chemical reactions involving 40+ chemical species are considered. Integration time step is 10 minutes, species can be combined into chemical families to facilitate integration. The module includes a radiative transfer model for the determination of photolysis rates. The module also includes heterogeneous reactions on NAT, ice and liquid particle surfaces.

Lagrangian mixing

Mixing is based on grid deformation of quasi uniform air parcel distributions. The contraction or elongation factors of the distances to 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 realistic manner.

Lagrangian sedimentation

Lagrangian sedimentation is calculated by following individual nitric acid trihydrate (NAT) particles that may grow or shrink by the uptake or release of HNO3 from/to the gas phase. These particle parcels are simulated independently from the Lagrangian air parcels. Their trajectories are determined using the horizontal winds and their vertical settling velocity that depends on the size of the individual particles. NAT particles are nucleated assuming a constant nucleation rate and they evaporate where temperatures grow too high. With this, a vertical redistribution of HNO3 (denitrification and renitrification) is determined.

CLaMS data sets

A chemistry transport model does 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 (UKMO)
  • 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 initialised from two-dimensional chemical models, chemistry-climate models, climatologies, or from correlations between chemical species or chemical species and dynamical variables.

See also

External links

References

The details of the model CLaMS are well documented and published in the scientific literature.
Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions
..... Click the link for more information.
Lagrangian, , of a dynamical system is a function that summarizes the dynamics of the system. It is named after Joseph Louis Lagrange. The concept of a Lagrangian was originally introduced in a reformulation of classical mechanics known as Lagrangian mechanics.
..... Click the link for more information.
General Circulation Models (GCMs) are a class of computer-driven models for weather forecasting, understanding climate and projecting climate change, where they are commonly called Global Climate Models.
..... Click the link for more information.
Time evolution is the change of state brought about by the passage of time, applicable to systems with internal state (also called stateful systems). In this formulation, time is not required to be a continuous parameter, but may be discrete or even .
..... Click the link for more information.
trajectory is the path a moving object follows through space. The object might be a projectile or a satellite, for example. It thus includes the meaning of orbit - the path of a planet, an asteroid or a comet as it travels around a central mass.
..... Click the link for more information.
This article is about the physical mechanism of diffusion. For alternative meanings, see diffusion (disambiguation).


Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
..... Click the link for more information.
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Wind shear can be broken down into vertical and horizontal components, with horizontal wind shear seen across
..... Click the link for more information.
equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator.
..... Click the link for more information.
equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation.
..... Click the link for more information.
The potential temperature of a parcel of fluid at pressure is the temperature that the parcel would acquire if adiabatically brought to a standard reference pressure , usually 1000 millibars.
..... Click the link for more information.
Anisotropy (pronounced with stress on the third syllable, IPA: /ˌænaɪˈsɒtrəpi/) is the property of being directionally dependent, as opposed to isotropy, which means homogeneity in all directions.
..... Click the link for more information.
Asad (Arabic: أسد) is one of many Arabic male given names for "lion", each denoting some aspect of the animal.
..... Click the link for more information.
University of Cambridge (often Cambridge University), located in Cambridge, England, is the second-oldest university in the English-speaking world and has a reputation as one of the world's most prestigious universities.
..... Click the link for more information.
UKMO may refer to
  • The Met Office (UK Meteorological Office)
  • The proposed UK Music Office in New York ( http://www.musicindie.com/clientdocuments/information/UKinUSexecsummary.pdf )

..... Click the link for more information.
Forschungszentrum Jülich GmbH (Research Centre Jülich) is a member of the Helmholtz-Gemeinschaft or Hermann von Helmholtz Association of National Research Centres and is one of the largest interdisciplinary research centres in Europe.
..... Click the link for more information.
Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions
..... Click the link for more information.
Meteorology (from Greek: μετέωρον, meteoron, "high in the sky"; and λόγος, logos, "knowledge") is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter