Chapter 3 – Meteorology (Air-Pollution Meteorology)

A set of Q&A flashcards summarizing definitions, processes, and relationships essential to Chapter 3 on Air-Pollution Meteorology.

What does Air-Pollution Meteorology study?

The atmospheric processes and phenomena that influence weather and the concentration of pollutants.

Name the four primary meteorological factors affecting pollutant concentration.

Wind speed and direction, temperature, atmospheric stability, and mixing height.

List four secondary meteorological parameters that influence air quality.

Rainfall/precipitation, humidity, solar radiation, and visibility.

How does high wind speed affect pollutant concentration near the emission source?

It carries pollutants away and dilutes them rapidly with surrounding air.

What is gustiness and why is it important?

Rapid fluctuations in wind speed; it enhances mixing and dilution of pollutants.

Which instrument measures wind speed?

An anemometer.

Define atmospheric stability.

The tendency of the atmosphere to encourage or suppress vertical air motion.

What is the normal environmental lapse rate given in the notes?

A temperature decrease of 6.4 °C per 1000 m (or 1000 ft).

What is a temperature inversion?

A reversal of the normal lapse rate where cold dense air is trapped below warmer air, preventing vertical mixing.

During an inversion, where are pollutants concentrated?

Below the inversion layer near ground level.

Why are inversions considered ‘stable’ atmospheric conditions?

Because vertical air movement (and thus mixing) is suppressed.

Describe a radiation inversion.

Night-time cooling creates a cool ground layer capped by warmer air, common in winter and valleys.

What causes a subsidence inversion?

Slowly sinking air in an anticyclone that warms adiabatically aloft and traps cooler air below.

What is mixing height?

The height above ground to which pollutants can be vertically mixed by turbulence.

State two meteorological factors that largely determine mixing height.

Wind direction and wind speed (also turbulence).

Explain rainfall’s ‘two-fold cleansing’ action on air pollutants.

Rain accelerates deposition of particulates and washes soluble gases from the atmosphere.

How does humidity affect air-pollution impacts?

High moisture can enhance corrosive reactions and promote fog formation with pollutants.

Why is solar radiation important to air quality?

It drives photochemical reactions among pollutants and provides surface heating that influences stability.

Define dry adiabatic lapse rate (DALR).

Temperature drop of unsaturated air: ~9.8 °C per km (5.4 °F per 1000 ft).

Define wet adiabatic lapse rate (WALR).

Cooling rate of saturated air (~6 °C per km) due to latent heat release during condensation.

What is a plume in air-pollution terminology?

The visible or invisible stream of emitted gases moving from a source into the atmosphere.

Define plume rise.

The vertical distance a hot plume travels above the stack due to buoyancy and momentum.

Give three factors that influence plume behaviour.

Stack height, diurnal variation, and seasonal variation (also stability, wind speed, etc.).

How does increasing stack height generally affect ground-level pollution?

It promotes better dilution aloft and reduces ground-level concentrations.

Write the formula for effective stack height (H).

H = h (physical stack height) + Δh (plume rise).

Which plume pattern is characterized by strong instability and a wavy path?

Looping plume.

Under what condition does a neutral plume occur?

When the environmental lapse rate equals the adiabatic lapse rate, allowing vertical rise until density equalizes.

Describe a fanning plume.

A horizontal plume with little vertical mixing, occurring under strong inversion conditions.

Which plume pattern is considered best for air quality and why?

Lofting plume, because strong upward diffusion prevents pollutants from reaching the ground.

Which plume pattern is worst for ground-level pollution and why?

Fumigating plume; pollutants are forced downward by an inversion layer above the stack.

What is a wind rose used for?

Graphically displaying the frequency and speed of winds from different directions at a location.

List four key inputs to plume dispersion theory.

Plume temperature, emission rate, stack height/diameter, and wind speed/direction (plus stability, topography).

Name two NEERI-developed instruments for meteorological measurement.

Wind Direction Recorder and Wind Speed Recorder (also temperature and solar-radiation measurement devices).