TAPM

Model name

TAPM

 

Full model name

The Air Pollution Model

 

URL

http://www.cmar.csiro.au/research/tapm/

 

Intended field of application

Simulation of meteorological fields, including in complex terrain. Dispersion of reactive and non-reactive pollutants from point, line, volume and area sources over local, urban and regional scales. Urban Airshed Modelling. Environmental Impact Assessments.

 

Model type and dimension

A three-dimensional prognostic meteorological and chemical transport integrated modelling system, with a Lagrangian particle model option for point source dispersion.

 

Model description summary

TAPM is a user-friendly PC-based model driven by a Graphical User Interface (GUI) that allows selection of all model input and configuration options (including access to supplied databases of surface information and synoptic analyses). TAPM predicts space- and time-varying local-scale meteorology and turbulence that is used to disperse and react air pollutants emitted from various sources, and predict ground-level pollution concentration. Wind data can be assimilated in a simulation. Model output can be processed through the GUI, including visualization, extraction of time-series, static plots, and summary statistics, using common packages. The model can be run in a nested mode, with its outermost domain nested in synoptic analyses/progoses. TAPM is suitable for impact distances ranging from hundreds of metres to a few hundred kilometres. It is applicable to air quality studies that involve simple to very rugged terrain, time-varying conditions such as the diurnal cycle, and the interaction of complex wind flows such as sea breezes and drainage winds. The system is readily applied to emissions from industrial facilities such as power stations, refinery complexes and smelters, as well as urban sources such as motor vehicles. TAPM also contains an algorithm to take account of the effect of building wakes on plume rise and dispersion. Concentration mean and variance can be calculated by the model.

 

Model limitations/approximations

The horizontal model domain size should be restricted in size to less than about 1500 km x 1500 km. The reasons for this restriction are that the model horizontal coordinate system neglect the curvature of the Earth. No large-scale cloud-convection parameterisation is included in the model. TAPM cannot be used to accurately represent deep atmospheric circulations or extreme weather events (e.g. thunderstorms, cyclones/hurricanes). The Generic Reaction Set (GRS) photochemistry option in the model may not be suitable for examining small perturbations in emissions inventories, particularly in VOC emissions, due to the highly lumped approach taken for VOCs in this mechanism.

 

Resolution

Temporal resolution

Timesteps set by model according to grid size (typically 5 to 300 seconds). Simulations from 1 day to years.

 

Horizontal resolution

Grid spacing 0.3 km to 30 km. Domain size up to 1500 km.

 

Vertical resolution

10m at ground. Typically 10 levels below a height of 1000 m.

 

Schemes

Advection & Convection

Semi-Lagrangian

 

Turbulence

Prognostic TKE - eddy dissipation rate, with counter-gradient fluxes. Cloud microphysics: water vapour, cloud water/ice, rain, snow. Gradual plume-rise in Lagrangian Mode. Building wake effects.

 

Deposition

Dry and wet deposition. Surface: Soil, Vegetation, Urban, and energy balance.

 

Chemistry

Tracers with optional first-order decay. Photochemistry uses a highly condensed scheme for smog formation (O3, NO2, NO, SO2, PM2.5, PM10, and Rsmog (for VOCs)). Dust Mode (PM2.5, PM10, PM20, PM30). See Technical Report on website for further details.

 

Solution technique

Finite differencing for meteorological and concentration equations. No grid stagger and second-order centred spatial differencing is used, with first-order differencing with a semi-implicit approach used for the time terms. Time-split approach whereby gravity-wave terms are solved on a smaller timestep than other terms. Plume-rise equations are solved using the 4th-order Runge-Kutta method with a timestep of 1 second. See Technical Report on website for further details.

 

Input

Availability and Validation of Input data

Default input data is supplied with the model (e.g. terrain, land use, soil, LAI, synoptic analyses), but user-defined data can also be input into the model. Pollution emissions data and building wake data need to be supplied by the user. Optionally, Wind data and pollutant background data and can also be assimilated by the model.

 

Emissions

Emission rates for all sources, and stack height, radius, temperature and exit velocity for point sources. For vehicles, can specify rates separately for petrol, diesel and LPG vehicles, at 25C. TAPM applies temperature correction throughout a simulation. Wood heater emissions are specified at 10C and biogenics at 30C and 1000 units PAR. TAPM applies correction throughout a simulation.

 

Meteorology

Meteorological variables are predicted by the model. Real wind data can be assimilated throughout a simulation.

 

Topography

The GUI uses the TAPM-supplied terrain height file and land-use file, both on an approximately 1-km spaced grid, to set up the grids for each nest. User-defined databases can be included.

 

Initial conditions

Initial fields for each nest are interpolated from TAPM-supplied synoptic global analyses (at 6-hourly intervals). Alternatively users can supply their own synoptic analyses. When setting up a simulation, it is recommended that at least one model spin-up day be allowed for, to enable the model variables to adjust to the terrain.

 

Boundary conditions

On the outermost grid, boundary values are interpolated in time and space from the 6-hourly synoptic analyses. Inner nests obtain their boundary conditions from the previous nest (one-way nesting).

 

Data assimilation options

Real wind data can be assimilated throughout a simulation.

 

Other input requirements

All meteorological input for the user-region supplied with the model. This includes terrain and land-use data. Latitude and longitude of centre of nested grids. Grid spacings and number of gridpoints in horizontal and vertical directions.

 

Output quantities

Meteorology: Hourly time series at any level for wind speed and direction, temperature, relative humidity, surface fluxes, as well as PBL height and micro-meteorological variables for any grid point. Vertical profile of hourly time series at any grid point (visually displayed) for wind, temperature, relative and specific humidity and TKE. Horizontal contours of the above variables at any hour. Concentrations: Time series of ground-level concentrations of pollutants averaged over time intervals from 1 hour to 24 hours are available at any gridpoint. Percentiles are calculated. Horizontal contours of maximum concentration and various percentile concentrations over the simulation period are calculated and displayed.

 

Portability and computer requirements

Portability

TAPM runs on a standard desktop PC under Windows.

 

CPU time

Model run-time varies from minutes to hours for cases studies, or from hours to days for an annual simulation, depending on grid configuration used.

 

Storage

An annual simulation needs about 10 Gb, although some files can be deleted when the simulation is completed.

última atualização a 15-04-2014
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