Introduction to Meteorology – Comprehensive Review

108 question-and-answer flashcards covering the major concepts, processes, instruments and terminology presented across the full Introduction to Meteorology lecture series.

What is the Earth’s atmosphere?

A gravitationally bound gaseous layer that surrounds the planet.

What is the Earth’s mean radiative temperature and the average surface air temperature?

–18 °C radiative, about 15 °C at the surface.

Which two gases make up roughly 99 % of dry air?

Nitrogen (~78 %) and oxygen (~21 %).

How is atmospheric nitrogen chiefly removed and returned?

Biological fixation by soil bacteria removes it; decomposition of organic matter returns it.

What two processes largely control atmospheric oxygen levels?

Consumption by respiration/oxidation and release by photosynthesis.

How does the concentration of water vapour differ between the tropics and the poles?

≈ 4 % of atmospheric gases in the humid tropics but < 1 % near the poles.

Why is water vapour meteorologically important?

Provides latent heat, drives condensation, and strongly absorbs terrestrial radiation.

List four natural sources of atmospheric CO₂.

Plant decay, volcanic eruptions, respiration, and ocean out-gassing (plus human activity).

Roughly how much more CO₂ is stored in the ocean than in the air?

≈ 50 times the atmospheric inventory.

State the roles of stratospheric and tropospheric ozone.

Stratospheric ozone absorbs harmful UV; tropospheric ozone is a pollutant and smog component.

Give three important natural or anthropogenic sources of methane (CH₄).

Anaerobic decomposition, ruminant digestion, and fossil-fuel extraction/biomass burning.

What are NOx and why are they significant?

Nitric oxide (NO) + nitrogen dioxide (NO₂); key in smog, ozone chemistry and acid rain formation.

Define atmospheric aerosols and name two of their meteorological roles.

Suspensions of solid or liquid particles; they scatter/absorb solar radiation and act as cloud-condensation nuclei.

Which bulk gases make up 99 % of air yet hardly influence weather?

Nitrogen and oxygen.

State the average thickness and lapse rate of the troposphere.

≈ 12 km thick (8 km at poles, 18 km at equator); temperature drops about 6.5 °C km⁻¹.

What happens to temperature with height in the stratosphere and why?

It rises because ozone absorbs ultraviolet radiation.

At what altitude and temperature does the mesopause occur?

≈ 80 km with temperatures near –90 °C.

Why is the thermosphere/ionosphere important for communications?

Ionised gases reflect radio waves back to Earth, enabling long-distance transmission.

Which three ingredients are required for Chapman ozone production?

Atomic oxygen (O), molecular oxygen (O₂) and solar UV radiation.

At what altitude is natural ozone formation most efficient?

Roughly 20–30 km (mid-stratosphere).

Which gas released from N₂O photolysis catalytically destroys ozone?

Nitric oxide (NO).

What unit measures total-column ozone?

The Dobson Unit (DU).

Below what DU value is the Antarctic ‘ozone hole’ defined?

220 DU during September–October.

What is the polar vortex and why does it matter for ozone loss?

A winter stratospheric wind whirl that isolates polar air, enabling chemical ozone depletion.

At what temperatures do PSC Types I and II form?

≈ –75 °C (Type I, nitric-acid particles) and ≈ –80 °C (Type II, ice particles).

In which year was the Montreal Protocol signed and when did it enter force?

Signed 1987, entered into force 1 January 1989.

What is the Kigali Amendment aimed at?

Cutting global HFC use > 80 % within about 30 years to curb greenhouse warming.

Define radiation in a meteorological context.

Energy transfer by electromagnetic waves emitted in all directions from a source.

Roughly what fractions of solar output are IR, visible and UV?

≈ 40 % infrared, 44 % visible, 10 % ultraviolet.

What is a black body?

An ideal object that absorbs and emits radiation with 100 % efficiency at all wavelengths.

State the inverse-square law for radiation flux.

Flux decreases with the square of distance from the source.

Express Wien’s displacement law qualitatively.

The wavelength of peak emission is inversely proportional to absolute temperature.

Summarise the Stefan–Boltzmann law.

Total black-body emission ∝ T⁴ (temperature to the fourth power).

Why is incoming solar radiation called ‘short-wave’?

Because its dominant wavelengths are < 4 µm, shorter than terrestrial IR.

Give the approximate fate of 100 units of solar energy at the top of the atmosphere.

51 absorbed by surface, 19 absorbed by atmosphere/clouds, 30 reflected/scattered to space.

Define albedo.

The fraction of incident radiation that a surface reflects.

How does Rayleigh scattering differ from Mie scattering?

Rayleigh acts on very small molecules, ∝ λ⁻⁴, favouring blue light; Mie occurs on larger aerosols with weak wavelength dependence.

State the accepted solar constant and its global mean value.

≈ 1368 W m⁻² at 1 AU; Earth-mean ≈ 342 W m⁻².

What is the ‘atmospheric window’?

Little-absorption band near 8–10 µm allowing IR to escape to space.

Name the two most important greenhouse gases.

Water vapour and carbon dioxide.

How is the radiative imbalance between surface and atmosphere balanced?

By upward sensible heat and latent heat fluxes.

Distinguish latent from sensible heat.

Latent heat involves phase change at constant temperature; sensible heat changes temperature with no phase change.

What does a pyrheliometer measure?

Direct solar (beam) radiation.

Which instrument records sunshine duration?

A heliograph (Campbell–Stokes heliofanograph).

Define heat and temperature.

Heat = energy transferred due to temperature difference; temperature = measure of average kinetic energy.

Contrast specific heat with heat capacity.

Specific heat is per unit mass; heat capacity is for the entire mass of an object.

List four radiative factors controlling air temperature.

Latitude, time of day, day of year, and cloud cover/albedo.

Why do continents heat and cool faster than oceans?

Lower specific heat, opaque surface, poor mixing and smaller evaporative cooling.

What is the average tropospheric lapse rate?

≈ 6.5 °C km⁻¹.

Define an urban heat-island.

Persistent warmer temperatures in densely built areas compared with nearby rural zones.

Briefly describe the hydrologic cycle’s energy driver.

Solar energy causes evaporation; water returns via condensation, clouds and precipitation.

Give the formula for relative humidity.

RH (%) = (actual vapour pressure / saturation vapour pressure) × 100.

What is dew-point temperature?

The temperature to which air must cool at constant pressure to reach saturation.

Name two ways air can become saturated.

Add water vapour (humidification) or cool the air isobarically.

Which instrument pair makes a psychrometer?

Dry-bulb and wet-bulb thermometers.

Explain an adiabatic process for a rising parcel.

It expands with falling pressure, does work, and cools without heat exchange.

State typical dry and moist adiabatic lapse rates.

≈ 9.8 °C km⁻¹ dry; 4–7 °C km⁻¹ saturated (varies with moisture content).

How is atmospheric stability diagnosed?

Compare parcel temperature with environmental temperature as it rises.

What surface radiative situation favours a temperature inversion?

Strong nocturnal radiative cooling of the ground beneath clear, calm skies.

Give two mechanisms that enhance instability.

Surface heating (insolation) and cold-air advection aloft.

List the three prerequisites for cloud formation.

Sufficient moisture, lifting mechanism, and condensation nuclei.

Name the four main lifting mechanisms.

Convection, orographic lift, convergence, and frontal lifting.

Identify one high-level, one mid-level and one low-level cloud genus.

High: Cirrus; Mid: Altostratus; Low: Stratus.

What visibility defines fog versus mist?

Fog < 1 km; mist 1–5 km.

Describe radiation fog formation.

Night-time cooling of moist air near the ground lowers temperature to dew-point.

Contrast collision–coalescence and Bergeron processes.

Collision–coalescence grows droplets in warm clouds; Bergeron grows ice crystals in mixed-phase cold clouds.

How does drop terminal velocity vary with size?

It increases as diameter increases.

Which two growth mechanisms supplement the Bergeron process?

Accretion (riming) and aggregation of ice crystals.

What does a standard rain gauge measure?

Liquid precipitation depth in millimetres (≙ litres m⁻²).

Define atmospheric pressure.

Force per unit area exerted by the weight of the overlying air column.

Why does humid air weigh less than dry air at the same temperature and pressure?

Water-vapour molecules (m ≈ 18) are lighter than average dry-air molecules (m ≈ 29).

What surface pattern characterises an anticyclone?

Closed isobars with higher pressure than surroundings; subsiding, diverging air.

Write the hydrostatic balance conceptually.

Downward gravity force balanced by upward vertical pressure-gradient force.

Name two common pressure-measuring instruments.

Mercury barometer and aneroid barometer (barograph for continuous recording).

List the three primary forces acting on horizontal wind.

Pressure-gradient force, Coriolis force and friction.

In which direction does the Coriolis force act in the Southern Hemisphere?

To the left of the motion.

Define geostrophic wind.

Wind resulting from balance between pressure-gradient and Coriolis forces, flowing parallel to isobars.

How does surface friction modify geostrophic flow?

Slows wind and causes it to cross isobars toward lower pressure.

What does the Beaufort scale describe?

Empirical estimate of wind speed based on observed sea or land conditions.

Why does the general circulation exist?

To redistribute surplus solar energy from low to high latitudes via air and ocean motions.

Name the three cells in the three-cell model.

Hadley, Ferrel and Polar cells.

Where are trade winds located and in which direction do they blow?

0–30° latitude; from NE in Northern Hemisphere, SE in Southern Hemisphere toward the ITCZ.

Why is the Ferrel cell called ‘indirect’?

It is driven by adjacent Hadley and Polar cells rather than direct heating.

What pressure belt lies near 30° latitude and why are winds there light?

Subtropical highs (‘horse latitudes’); descending air produces weak pressure gradients.

What mid-latitude feature marks the Polar Front?

A belt of low pressure where polar easterlies meet mid-latitude westerlies.

Where is the polar-front jet stream typically found?

Near 9–12 km altitude around 45–60° latitude where horizontal temperature gradients are strong.

How do western boundary currents affect climate?

They transport warm water poleward along east coasts of continents, moderating climate.

Define thermohaline circulation.

Deep-ocean flow driven by density differences caused by temperature and salinity variations.

What is an air mass?

A large body of air with uniform temperature and humidity horizontally.

Describe typical weather with a warm front.

Widespread stratiform clouds, steady light-to-moderate precipitation, gradual temperature rise.

Describe typical weather with a cold front.

Steep uplift, cumuliform clouds, short-lived heavy showers or thunderstorms, temperature drop.

Distinguish cold-type from warm-type occlusion.

Cold-type: very cold air undercuts cold air ahead; warm-type: cool air rides over colder air.

What defines a stationary front?

Neither air mass advances; winds blow nearly parallel to the frontal zone.

List three ingredients for thunderstorm formation.

Moisture, instability and a lifting mechanism.

Identify the three stages of a single-cell thunderstorm.

Cumulus (up-draft), mature (up- & downdrafts, precipitation), dissipating (downdrafts dominate).

What is a squall line?

A linear mesoscale band of organised thunderstorms, usually ahead of a cold front.

Define a supercell thunderstorm.

A highly organised, rotating (mesocyclone) storm capable of severe weather, large hail and tornadoes.

How is tornado intensity classified?

Enhanced Fujita (EF) scale from EF-0 to EF-5 based on damage.

Give the wind-speed thresholds for tropical-cyclone stages.

< 63 km h⁻¹ depression, 63–118 km h⁻¹ tropical storm, ≥ 119 km h⁻¹ hurricane/typhoon.

Provide the UNFCCC definition of climate change.

A climate change attributable directly or indirectly to human activity that alters atmospheric composition.