The Air Pollution Model (TAPM)

Description

Air pollution models that can be used to predict hour by hour pollution concentrations for periods of up to a year, are generally semi-empirical/analytic approaches based on Gaussian plumes or puffs. These models typically use either a simple surface based meteorological file or a diagnostic wind field model based on available observations. TAPM is different to these approaches in that it solves approximations to the fundamental fluid dynamics and scalar transport equations to predict meteorology and pollutant concentration for a range of pollutants important for air pollution applications. TAPM consists of coupled prognostic meteorological and air pollution concentration components, eliminating the need to have site-specific meteorological observations. Instead, the model predicts the flows important to local-scale air pollution, such as sea breezes and terrain induced flows, against a background of larger-scale meteorology provided by synoptic analyses. The meteorological component of TAPM is an incompressible, non-hydrostatic, primitive equation model with a terrain-following vertical coordinate for three-dimensional simulations. The model solves the momentum equations for horizontal wind components, the incompressible continuity equation for vertical velocity, and scalar equations for potential virtual temperature and specific humidity of water vapour, cloud water/ice, rain water and snow. The Exner pressure function is split into hydrostatic and non-hydrostatic components, and a Poisson equation is solved for the non-hydrostatic component. Explicit cloud microphysical processes are included. The turbulence terms in these equations have been determined by solving equations for turbulence kinetic energy and eddy dissipation rate, and then using these values to represent vertical fluxes by a gradient diffusion approach, including counter-gradient terms. A vegetative canopy, soil scheme, and urban scheme are used at the surface, while radiative fluxes, both at the surface and at upper levels, are also included. The air pollution component of TAPM, which uses the predicted meteorology and turbulence from the meteorological component, consists of four modules. The Eulerian Grid Module (EGM) solves prognostic equations for the mean and variance of concentration. The Lagrangian Particle Module (LPM) can be used to represent near-source dispersion more accurately. The Plume Rise Module is used to account for plume momentum and buoyancy effects for point sources. The Building Wake Module allows plume rise and dispersion to include wake effects on meteorology and turbulence. The model also includes gas-phase photochemical reactions based on the Generic Reaction Set, gas- and aqueous-phase chemical reactions for sulfur dioxide and particles, and a dust mode for total suspended particles (PM2.5, PM10, PM20 and PM30). Wet and dry deposition effects are also included.

Purpose

TAPM is a model developed to estimate the spread and impact of air pollution. It is a meteorological, prognostic air pollution model.

Latest Version	4
State of Development	Please Select

Scope

Steady State or Dynamic	Unknown

Input & Output Data

Accessibility

Open/Closed Source	Please Select

User Information

User Interface	Please Select
Ease of Use	Moderate
Use in Policy Process	Plan (Policy Formulation), Do (Policy Implementation)
Documentation	http://www.cmar.csiro.au/research/tapm/docs/CSIRO-TAPM_V4_Information_sheet.pdf http://www.cmar.csiro.au/research/tapm/docs/tapm_v4_user_manual.pdf http://www.cmar.csiro.au/research/tapm/docs/tapm_v4_technical_paper_part1.pdf

Technical Considerations

Model Structure	The meteorological component of TAPM is an incompressible, optionally non-hydrostatic, primitive equation model with a terrain-following vertical coordinate for three-dimensional simulations. It includes parameterisations for cloud/rain/snow micro-physical processes, turbulence closure, urban/vegetative canopy and soil, and radiative fluxes. The model solution for winds, potential virtual temperature and specific humidity, is weakly nudged with a 24-hour e-folding time towards the synoptic-scale input values of these variables. Note that the horizontal model domain size is restricted in size to less than 1500 km x 1500 km, as the model equations neglect time zones, the curvature of the earth and assume a uniform distance grid spacing across the domain.
Keywords	air quality, pollution, meteorological
Links	http://www.cmar.csiro.au/research/tapm