GR ESS 210 Ch5 lecture Sept26&28, 2023

Heat properties of water

Describes the heat energy transferred during phase changes between solid, liquid, and gas states of water.

Humidity

The amount of water vapor present in the air.

Cloud formation

The process by which clouds are formed in the atmosphere.

Precipitation

Forms of water that fall from the atmosphere to the Earth's surface, including rain, snow, freezing rain, sleet, and hail.

Air masses

Large bodies of air with similar temperature and moisture characteristics.

Atmospheric lifting mechanisms

Different processes that cause air to rise and form clouds and precipitation.

Midlatitude cyclonic storm system

A type of storm system that forms in the midlatitudes and is associated with low pressure and cyclonic circulation.

Violent weather

Thunderstorms, derechos, tornadoes, and tropical cyclones, characterized by their formation and characteristics.

Water's unique properties

Pure water is colorless, odorless, and tasteless, and it occurs as a solid, liquid, and gas.

Phase changes and heat exchange

Describes the changes in water's physical state and the heat energy involved in these changes.

Vapor pressure

The share of air pressure made up of water vapor molecules.

Specific humidity

The mass of water vapor per mass of air at a specified temperature.

Saturation vapor pressure

The maximum amount of water vapor that air can hold at a given temperature.

Dew-point temperature

The temperature at which air becomes saturated and net condensation begins to form water droplets. The temperature at which air with a given humidity will reach saturation when cooled without changing its pressure.

Saturation mixing ratio

The mass of water vapor that can be held in a kilogram of dry air at saturation.

Relative Humidity

A ratio (expressed as a percentage) of the amount of water vapor that is actually in the air compared to the maximum water vapor possible in the air at a given temperature.

Mixing Ratio

The actual amount of water in a parcel of air, expressed in grams. A measure of the mass of a specific gas component relative to the mass of the remaining gaseous components in a sample of air.

Saturation Mixing Ratio

The maximum amount of water vapor that a parcel of air can hold at a given temperature, expressed in grams.

Condensation

The process by which water vapor changes into liquid or solid form, usually forming clouds, fog, or precipitation.

Atmospheric Humidity

The amount of moisture present in the air.

Saturation

When the rate of evaporation and the rate of condensation reach equilibrium, and the air is saturated with the maximum water vapor for its temperature.

Psychrometer

An instrument used to measure relative humidity, consisting of a dry-bulb thermometer and a wet-bulb thermometer.

Dew Point

The temperature at which water vapor saturates from an air mass into liquid or solid, usually forming rain, snow, frost, or dew.

Atmospheric Stability

The tendency of an air parcel, with its water vapor cargo, either to remain in place or to change vertical position by ascending or descending.

Adiabatic Process

The process of temperature change in a parcel of air as it rises or descends without any heat exchange with the surrounding environment.

Dry Adiabatic Rate (DAR)

The rate at which a dry parcel of air cools or warms as it rises or descends, approximately 10 degrees Celsius per 1000 meters.

Moist Adiabatic Rate (MAR)

The rate at which a moist parcel of air cools or warms as it rises or descends, approximately 6 degrees Celsius per 1000 meters.

Adiabatic principle

The physical principle that a gas cools as it expands and warms as it is compressed, provided that no heat flow in or out of the gas during the process.

Dry adiabatic lapse rate

Rate at which rising air is cooled by expansion when no condensation is occurring; 10 ℃ per 1000m (5.5 ℉ per 1000ft).

Moist adiabatic lapse rate

Rate at which rising air is cooled by expansion when condensation is occurring; ranges from 4 to 9 ℃ per 1000m (2.2 to 4.9 ℉ per 1000ft).

Dry adiabatic rate (DAR)

The rate at which "dry" air cools by expansion (if ascending) or heats by compression (if descending). "Dry" refers to air that is less than saturated. Average DAR is 10 C°/1000 m (5.5 F°/1000 ft).

Moist adiabatic rate (MAR)

The rate at which an ascending air parcel that is moist, or saturated, cools by expansion. Average MAR is 6 C°/1000 m (3.3 F°/1000 ft). MAR varies with moisture content and temperature.

Lapse rate

Rates of temperature change with change in altitude. Normal lapse rate is the average decrease in temperature with increasing altitude, a value of 6.4°C/1000m. Environmental lapse rate is the actual lapse rate at a particular time and place. It can vary by several degrees per thousand meters.

Condensation

Water moving from a vapor to a liquid state.

Freezing

Water moving from a liquid to a solid state.

Deposition

Water moving from a vapor to a solid state.

Condensation nucleus

A tiny bit of solid matter (aerosol) in the atmosphere on which water vapor condenses to form a tiny water droplet.

Clouds

Made up of water droplets, ice particles, or a mixture of both, suspended in air.

Orographic uplift

Occurs when air is forced to rise because of the physical presence of elevated land. As the parcel rises, it cools as a result of adiabatic expansion at a rate of approximately 10° Celsius per 1000 meters until saturation.

Radiative cooling

Occurs when the Sun is no longer supplying the ground and overlying air with energy derived from solar insolation (e.g., night). Instead, the surface of the Earth now begins to lose energy in the form of longwave radiation which causes the ground and air above it to cool.

Cloud Formation Processes

The processes involved in the formation of clouds, including the condensation of moisture droplets and the role of cloud-condensation nuclei.

Moisture Droplets

Tiny droplets of moisture that make up clouds, typically around 20 µm in diameter.

Cloud Types and Identification

The classification of clouds based on altitude, shape, and form, including stratiform, cumuliform, and cirroform clouds.

Altitude and shape

Key factors in cloud classification, with three basic shapes - flat, puffy, and wispy - and four primary altitude classes - low, middle, high, and vertically developed.

Cloud Families

High clouds, middle clouds, low clouds, and clouds of vertical development.

Principal Cloud Types

Specific cloud types classified by altitude and form, including altocumulus, cirrostratus, cirrus, cumulonimbus, nimbostratus, stratus, and cumulus.

Cirrus Clouds

High, thin, wispy clouds composed of ice crystals that form at the top of the troposphere.

Stratiform Clouds

Blanket-like layers of clouds that cover large areas, such as stratus clouds.

Cumuliform Clouds

Globular masses of clouds associated with rising moist air, such as cumulus clouds.

Nimbus Clouds

Clouds of any type that produce precipitation, such as cumulonimbus clouds.

Cumulonimbus Development

The development of cumulonimbus clouds, including the presence of ice crystals, anvil tops, and heavy rain.

Fog

A cloud layer on the ground with restricted visibility, formed by various processes such as advection fog, evaporation fog, upslope fog, valley fog, and radiation fog.

Precipitation

The process by which water droplets or ice crystals fall from the atmosphere due to gravity.

Ice crystals

Large crystals that form in clouds with temperatures below freezing, due to differences in vapor pressure between ice crystals and supercooled water droplets.

Condensation nuclei

Particles in the atmosphere that serve as a surface for water vapor to condense onto, forming cloud droplets.

Deposition nuclei

Particles in the atmosphere that promote the formation of ice crystals at temperatures just below zero degrees Celsius.

Supercooled water droplets

Liquid water droplets that remain in a liquid state at temperatures below freezing.

Snow crystals

Ice crystals that form in cool clouds when water vapor evaporates from supercooled liquid cloud drops and deposits on ice crystals.

Raindrops

Water droplets that have grown in size through collision and coalescence with other droplets in a cloud, and have become heavy enough to fall due to gravity.

Freezing rain

Raindrops that encounter a surface with a temperature below 0°C and quickly turn into ice upon contact.

Sleet

Transparent or translucent spheres of frozen water that form when raindrops freeze into ice pellets during their descent through a colder layer of the atmosphere.

Hail

Frozen precipitation that is more than 5 millimeters in diameter, characterized by concentric shells of ice and alternating cloudy and clear layers.

Weather

The short-term, day-to-day condition of the atmosphere at a specific location and time.

Climate

The long-term average of weather conditions and extremes in a region, typically measured over decades.

Weather patterns

The result of interactions between different air masses, producing changes in temperature, air pressure, humidity, and wind speed and direction.

Source Region

The region where an air mass acquires its characteristics.

Continental

Referring to air masses that form over land and are typically dry.

Maritime

Referring to air masses that form over water and are typically moist.

Equatorial

A source region with warm temperatures near the equator.

Tropical

A source region with warm temperatures in the tropics.

Polar

A source region with cold temperatures near the poles.

Arctic

A source region with extremely cold temperatures in the Arctic region.

Continental Arctic (cA)

A cold and dry air mass formed in the Arctic region.

Continental Polar (cP)

A cold and dry air mass formed over land in polar regions.

Maritime Polar (mP)

A cool and moist air mass formed over water in polar regions.

Maritime Tropical (mT)

A warm and moist air mass formed over water in tropical regions.

Continental Tropical (cT)

A hot and dry air mass formed over land in tropical regions.

Air Mass Modification

The process by which air masses change their temperature and moisture characteristics as they move over different land surfaces.

Lake-Effect Snow

Heavy snowfall that occurs downwind of the Great Lakes due to the interaction of cold air masses with the warm lake waters.

Convergent Lifting

Air flows towards an area of low pressure, causing the air to converge and ascend, leading to cooling and condensation.

Convectional Lifting

The air above warmer surfaces is heated and rises, creating convection currents and lifting the air mass.

Cold Front

The leading edge of a cold air mass, characterized by a rapid temperature drop and heavy precipitation.

Warm front

A transition zone in the atmosphere where warm subtropical air replaces cold polar air, characterized by rising temperatures, light precipitation, and southerly winds.

Cold front

A transition zone in the atmosphere where cold, dry stable air displaces warm, moist unstable air, characterized by falling temperatures, heavy precipitation, and shifting winds.

Occluded front

A weather front formed when a fast-moving cold front overtakes a slower-moving warm front, resulting in the lifting of warm air and precipitation.

Front

The surface or boundary of contact between two different air masses associated with a midlatitude cyclone, including cold fronts, warm fronts, stationary fronts, and occluded fronts.

Frontal lifting

The forced uplifting of warm air caused by the sloping of warm air over cold air at a front, leading to condensation and the possibility of precipitation.

Stationary front

A frontal zone where air masses are not moving against each other, resulting in little or no relative motion.

Midlatitude cyclone

Large traveling atmospheric cyclonic storms in the mid-latitudes, formed by the dynamic interaction of warm tropical and cold polar air masses at the polar front.

Adiabatic cooling

The cooling of air as it rises and expands due to a decrease in pressure, leading to the formation of clouds and possibly precipitation.

Anticyclone

A high-pressure system characterized by outward spiraling and sinking air, resulting in fair skies.

Midlatitude cyclone

A large inspiral of air that forms, intensifies, and dissolves along the polar front in middle and higher latitudes.

Wave cyclone

Another term for a midlatitude cyclone, dominant in middle and higher latitudes.

Polar front

The location where two very different air masses, dense cold polar air and warm humid subtropical air, are in contact and poised to clash.

Cyclogenesis

The process of the formation of a cyclone at the polar front.

Cold front

The boundary along which cold air actively pushes southward.

Warm front

The boundary along which warm air actively moves northeastward.

Occluded front

When the faster-moving cold front overtakes the warm front, shutting off the warm air from the ground.

Precipitation

The formation of rain, snow, sleet, or hail that occurs as the two fronts begin to move.

Counterclockwise flow

The direction of airflow in the Northern Hemisphere around a low-pressure center in a midlatitude cyclone.