Atmospheric Moisture and Concept of Air Mass

A comprehensive collection of vocabulary flashcards covering atmospheric moisture, condensation, precipitation, air mass concepts, cyclones, and jet streams based on physical geography lecture notes.

Absolute Humidity

The total mass of water vapor present in a given volume of air, expressed in grams per cubic meter ($g/m^3$).

Specific Humidity

The mass of water vapor present in a unit mass of air, including both water vapor and dry air, expressed in grams per kilogram ($g/kg$).

Relative Humidity

The ratio of the current amount of water vapor in the air to the maximum amount the air can hold at a given temperature, expressed as a percentage.

Humidity Capacity

The maximum amount of water vapor that air can contain at a specific temperature and pressure.

Condensation

The process by which water vapor in the air changes into liquid water or ice when the air cools or becomes saturated.

Dew Point

The temperature at which air becomes fully saturated ($100\%$ relative humidity) and water vapor begins to condense into liquid.

Condensation Nuclei

Microscopic particles like dust, pollutants (aerosols), or minute salt particles (hygroscopic nuclei) that provide surfaces for water vapor to condense upon.

Dew

Water droplets formed when moist air comes into contact with cooler surfaces that are at or below the dew point but above freezing.

Frost

Ice crystals formed when the air temperature drops below the freezing point and water vapor changes directly into a solid through sublimation.

Fog

A collection of tiny water droplets suspended in the air near the ground, formed when air near the surface becomes saturated.

Mist

A form of condensation similar to fog but less dense, with visibility typically between $1$ to $2\,km$.

Haze

Suspension of extremely fine water droplets often mixed with dust or pollution particles, with visibility ranging from $3$ to $5\,km$.

Smog

A combination of smoke and fog that forms when pollutants mix with moisture in the air.

Vog

Volcanic fog created by gases such as sulfur dioxide ($SO_2$) reacting with sunlight, oxygen, dust, and water vapor.

Latent Heat of Condensation

The heat energy released into the surrounding air when water vapor condenses into liquid water.

Adiabatic Process

A thermodynamic process where a parcel of air changes its temperature due to expansion or compression without exchanging heat with its surroundings.

Dry Adiabatic Lapse Rate

The rate at which an unsaturated rising air parcel cools, which is about $10^\circ C/km$.

Wet Adiabatic Lapse Rate

The rate at which a saturated rising air parcel cools, approximately $5-6^\circ C/km$, slowed by the release of latent heat.

Virge / Virga

Precipitation that evaporates or sublimates before reaching the Earth’s surface.

Convectional Rainfall

Rainfall occurring when solar heating causes warm, moist air to rise rapidly, cooling and condensing into cumulonimbus clouds.

Orographic Rainfall

Precipitation formed when moist air is forced to ascend a mountain range, cooling and condensing on the windward side.

Frontal Rainfall

Precipitation occurring when two air masses of different temperatures and densities meet, forcing warmer air to rise.

Air Mass

A large body of air with relatively uniform temperature, humidity, and pressure across its horizontal extent.

Maritime Tropical (mT)

A warm and humid air mass originating over tropical oceans and seas.

Continental Polar (cP)

A cold and dry air mass originating over polar landmasses like tundras or snow-covered areas.

Front

The boundary or transition zone between two contrasting air masses.

Warm Front

A front where a warm air mass advances and gently rises over a colder air mass, typically producing nimbostratus clouds and steady precipitation.

Cold Front

A front where a dense cold air mass advances and forces warm air to rise rapidly, often leading to cumulonimbus clouds and intense thunderstorms.

Stationary Front

A standoff between two air masses where neither advances, leading to prolonged cloudiness and precipitation.

Occluded Front

A complex front formed when a fast-moving cold front overtakes a warm front, lifting the warm air completely off the ground.

Frontogenesis

The process of strengthening or intensifying a front due to temperature and pressure gradients.

Frontolysis

The process of weakening or the dissipation of a front.

Cyclone

A large-scale low-pressure system characterized by inward-spiraling winds and ascending air motion.

Anticyclone

A high-pressure system characterized by descending air that moves outward from the center, typically bringing clear skies and stable weather.

Coriolis Effect

The force resulting from Earth's rotation that deflects winds counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Eye

The central region of a tropical cyclone, characterized by calm weather, clear skies, and descending air.

Eye Wall

The region immediately surrounding the eye of a cyclone, containing the most intense winds and heaviest rainfall.

Western Disturbances

Temperate cyclones that bring winter rainfall to northern India and snowfall to the Himalayas.

Supercell

A highly organized thunderstorm with a rotating updraft that can serve as the birthplace of tornadoes.

Tornado

A violent, rotating column of air extending from a cumulonimbus cloud to the ground, characterized by a funnel shape and high wind speeds.

Enhanced Fujita Scale

A scale (EF0 to EF5) used to measure the intensity of tornadoes based on the damage inflicted on structures.

Jet Streams

Narrow bands of high-speed, fast-flowing geostrophic winds located near the tropopause.

Geostrophic Winds

Steady, high-altitude winds that flow parallel to isobars due to a balance between the pressure gradient force and the Coriolis effect.

Rossby Waves

Large, wavy meandering patterns exhibited by jet streams due to variations in atmospheric pressure.

Subtropical Jet Stream

A high-speed wind current at $25^\circ$ to $35^\circ$ latitude driven primarily by Earth's rotation and Hadley cell circulation.

Polar Jet Stream

A narrow band of fast-moving winds near the polar front ($60^\circ$ latitude) driven by the temperature gradient between polar and mid-latitude regions.