Air Pollution Meteorology

Transcription

1 Air Pollution Meteorology

2 Government Pilots Utilities Public Farmers Severe Weather Storm / Hurricane Frost / Freeze Significant Weather Fog / Haze / Cloud Precipitation High Resolution Weather & Dispersion Disaster Planners Emergency Response Emergency Response Risk Assessment Natural Disasters Accidents / Terrorism Air Quality Urban Smog Regional Air Quality Federal / State / Local Gov t Utilities (Pollution Credit)

3 Atmospheric Dispersion Dispersion = Transport (Advection) + Diffusion Transport by Mean Wind Diffusion by Turbulence

4 Atmospheric Dispersion Automobile Emissions Dust / Debris from Explosions / Volcanoes Pesticides / Pests Releases from Chemical / Refining Facilities Releases of Chemical / Biological Material Smoke / Soot from Burning Biomass / Oil Fields Smoke / Soot from Power Plants Radioactivity from Nuclear Plants / Nuclear Tests

5 Atmospheric Dispersion is Interdisciplinary Physics Fluid Dynamics Advection Diffusion Turbulence Thermodynamics Atmospheric Stability Phase Changes Radiation Transport Particle Physics Transport Diffusion Microphysics

6 Atmospheric Dispersion is Interdisciplinary Meteorology Cloud and Mesoscale Dynamics Atmospheric Microphysics Phase Changes Particle Growth Scavenging Atmospheric Chemistry Homogeneous and Heterogeneous Reactions Planetary Boundary Layer Physics Surface Physics (Moisture and Energy) Mathematics Numerical Analysis and Methods Turbulence and Chaos

7 Dispersal Hazard Scales Global Continental Regional Local Radiation Forced Air-Mass Movement Air-Mass Boundaries Local Topography Climate Driven Topographic Forcing Surface Heating Surface Heating Latent Heat Release Urban Effects Jet Stream Baroclinic Systems Fronts Convection Long-term Weather Squall Lines Downslope Flow Mountain Waves Sea/Land Breeze

8 Mt. St. Helens May 18, 1980

9 Mt. St. Helens May 18, 1980

10 Bhopal: The terrain surrounding Bhopal, the urban heat island effect, and the lake effect all contributed to the m a g n i t u d e o f t h e disaster.

11 Governing Factors for Atmospheric Dispersion Free Troposphere Wind (for Horizontal Transport) Convection (for Vertical Transport) Precipitation (for Removal) Turbulence (for Diffusion) Planetary Boundary Layer Orography Sea Breeze / Land Breeze Circulations Urban / Canopy Effects Soil Moisture

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13 PBL depth and structure Over oceans, the PBL depth varies relatively slowly in space and time The general nature of the PBL is to be thinner in HP regions than in LP regions

14 Planetary Boundary Layer Physics Strongly Influences the Near Surface Circulation Urban Canopy Land/Sea Breezes Sea Breeze Land Breeze Orography Low Level Jet

15 Surface forcings The surface forcings Frictional drag Heat transfer Evaporation and transpiration Pollutant emission Terrain induced flow modification It is ground that warms and cools in response to the radiation, which in turn forces changes in the PBL via transport processes Turbulence is one of the important transport processes

16 PBL depth and structure Viscous sublayer (molecular dissipation dominant) Surface layer (small scale eddies dominant) Mixed layer (large scale eddies dominant) Residual layer is not considered within PBL concept

17 Planetary Boundary Layer

18 Dispersion in the convective BL The ML is characterized by intense mixing in an unstable situation where thermals of warm air rise from the ground The ML reaches its max depth in late afternoon and grows by entraining or mixing down into it. Pollutants exhibit a characteristic looping behavior

19 Dispersion in the nocturnal BL Smoke emissions into the stable SL fan out (fanning) in the horizontal with little vertical dispersion other than wavelike oscillations Smoke emissions into the neutral RL spread with an almost equal rate in the vertical and horizontal, cone like shape (conning)

20 Dispersion in the transitional zones Smoke plumes in the RL may disperse to the point where the bottom of the plume hits top of the SBL. The strong stability reduces downward mixing, (lofting) After sunrise a new ML begins to grow, eventually reaching the height of the elevated plume from the previous night (fumigation)

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