Volume 2 Airviro User’s Reference Working with the Dispersion Module How to simulate the dispersion of pollutants Working with the Dispersion Module How to simulate the dispersion of pollutants Amendments Version Date changed Cause of change Signature 3.11 Ago2007 Upgrade GS 3.12 January2009 Upgrade GS 3.13 January2009 Upgrade GS 3.20 May 2010 Upgrade GS Contents 2.1 Introduction ..................................................................................................... 7 2.1.1 Why You Need to Use Dispersion Models .............................................................. 7 2.1.1.1 What’s the Use of Dispersion Simulations... ........................................................................... 7 2.1.1.2 How Can Airviro Help? ............................................................................................................ 7 2.1.2 Model Assumptions ................................................................................................ 7 2.1.3 Brief description of the available models ..................................................................................... 8 2.1.4 How does Dispersion Module client work? ........................................................... 13 2.1.5 Guidance for the beginner: ................................................................................... 13 2.1.6 Overview of the Dispersion Module Main Window ................................................ 15 2.1.6.1 Changing Weather Conditions – Model settings ................................................................... 15 2.1.6.2 Specifying Emissions ............................................................................................................ 16 2.1.6.3 Submitting a Dispersion for Calculation ................................................................................ 16 2.1.6.4 Viewing Existing Dispersion Calculations ............................................................................. 16 2.1.6.5 Finding Local Values ............................................................................................................. 17 2.1.6.6 Using Receptor Points .......................................................................................................... 17 2.1.6.7 Map Functions....................................................................................................................... 17 2.1.6.8 Sub menus on the left-hand side in the Dispersion main windows ...................................... 17 2.1.6.9. What is the grid resolution of the simulation? ........................................................................... 20 2.2 The Gauss Model .......................................................................................... 23 2.2.1 Examples Based on the Case Weather Condition ................................................ 23 2.2.2 Ordering a Calculation .......................................................................................... 24 2.2.3 Examples Based on Emission for a Specific Hour ................................................ 29 2.2.4 Using Scenario Weather Conditions ..................................................................... 31 2.2.5 Using the Advanced Result Options ..................................................................... 34 2.3 The Street Canyon Model ............................................................................. 37 2.3.1 Street Canyon Overview ...................................................................................... 37 2.4 The Grid Model ............................................................................................. 40 2.4.1 Looking at Dispersions for a Specific Time Period ................................................ 40 2.4.2 Looking at Dispersions for a Season .................................................................... 43 2.5 The Heavy Gas Model ................................................................................... 44 2.5.1 Simulation of a Continuous Liquid Leak ...................................................................... 44 2.5.2 Simulation of a Tank Burst .......................................................................................... 46 2.6 Introduction to the Receptor Model ............................................................ 49 2.6.1 Where is this pollution coming from? .................................................................... 49 2.6.2 For proper use of the Receptor module: ............................................................... 49 2.6.4 Overview of the Receptor Model Settings Window ............................................... 51 2.6.5. Source Location ................................................................................................... 54 2.6.6 Emission Estimation ............................................................................................. 56 Swedish Meteorological and Hydrological Institute, SE-601 76 Norrköping, Sweden Page 3 (113) Phone: +46-11 495 8000, Fax: +46-11 495 8001 2.7 Aermod Model ............................................................................................... 59 2.8 OSPM Model .................................................................................................. 62 2.9 MATCH Model ............................................................................................... 66 Appendix 2A:The Wind Model - Calculation of the Wind Fields .......................... 68 2A.1 Principles of Wind Field Calculations ........................................................................... 68 2A.1.1 Wind Model Equations ................................................................................................................ 68 2A.1.2 Initialisation ................................................................................................................................. 69 2A.1.3 Stability and Turbulence Estimation - Preprocessing of Meteorological Data ............................ 69 2A.1.4 Mesoscale Interpolation .............................................................................................................. 72 2A.1.5 Procedures for Solving the Wind Model Equations .................................................................... 73 2A.1.6 Numerical Methods ..................................................................................................................... 73 2A.1.7 Reference Literature ................................................................................................................... 73 Appendix 2B:Results from Verification Studies ................................................... 74 Appendix 2C: The Gauss Dispersion Model ......................................................... 77 2C.1 Introduction ................................................................................................................. 77 2C.2 When to Use the Gauss Plume Model ......................................................................... 77 2C.2.1 Source Type Definitions .............................................................................................................. 78 2C.3 Plume Rise Formulation .............................................................................................. 78 2C.4 Building Downwash ..................................................................................................... 81 2C.5 The Gaussian Plume Model ........................................................................................ 82 Appendix 2D:The Eulerian Advection-Diffusion Grid Model ............................... 84 2D.1 Introduction ................................................................................................................. 84 2D.2 Formulation of the Grid Model ..................................................................................... 84 2D.2.1 Numerical Methods ..................................................................................................................... 85 2D.2.2 The Numerical Grid, Coordinate Transformations ...................................................................... 86 2D.2.3 The Turbulent Exchange Coefficient .......................................................................................... 86 2D.2.4 The Three-Dimensional Wind Field ............................................................................................ 89 2D.2.5 Source Initialisation ..................................................................................................................... 89 2D.3 Particle Deposition ...................................................................................................... 89 2D.3.1 Dry Deposition of Gases and Non-Gravitating Particles ............................................................ 89 2D.3.2 Wet Deposition ........................................................................................................................... 91 2D.3.3 Particle Settling ........................................................................................................................... 91 Appendix 2E:Street Canyon Model ........................................................................ 92 2E.1 Model Description ........................................................................................................ 92 Appendix 2F:The Heavy Gas Model ....................................................................... 94 2F.1 Continuous Release or a Leakage From a ”Small” Hole .............................................