Term
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Definition
| the amount of heat required to raise the temperature of 1 gram of water 1ºC |
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Term
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Definition
| when the heat used does not produce a temperature change; latent means "hidden" |
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Term
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Definition
| the amount of calories needed to melt one gram of ice (80 calories) |
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Term
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Definition
| the reverse process of heating that releases calories into the environment |
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Term
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Definition
| freezing releases 80 calories per gram of ice to the environment |
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Term
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Definition
| the process of converting a liquid to a gas (vapor) |
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Term
| latent heat of vaporization |
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Definition
| the energy absorbed by water molecules during evaporation that is used to give them the motion needed to escape the surface of the liquid and become a gas |
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Term
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Definition
| the reverse process of evaporation occurs when water vapor changes to the liquid state |
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Term
| latent heat of condensation |
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Definition
| water-vapor molecules release energy in an amount equivalent to what was absorbed during evaporation |
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Term
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Definition
| the conversion of a solid directly to a gas without passing through the liquid state |
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Term
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Definition
| refers to the reverse process of sublimation, the conversion of a vapor directly to a solid |
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Term
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Definition
water vapor that is deposited as ice on solid objects such as grass or windows
also known as hoar frost or just frost |
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Term
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Definition
| the most important gas in the atmosphere when it comes to understanding atmospheric processes |
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Term
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Definition
| the general term for the amount of water vapor in the air |
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Term
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Definition
| that part of the total atmospheric pressure that can be attributed to the water-vapor content |
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Term
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Definition
| when the number of vapor molecules returning to the surface of water will balance the number leaving |
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Term
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Definition
| the mass of water vapor in a unit of air compared to the remaining mass of dry air |
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Term
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Definition
| a ratio of the air's actual water-vapor content compared with the amount of water vapor required for saturation at that temperature (and pressure) |
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Term
| water vapor content remains constant |
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Definition
| a decrease in temperature results in an increase in relative humidity |
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Term
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Definition
the temperature to which a parcel of air would need to be cooled to reach saturation
also known as dew point |
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Term
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Definition
| unlike relative humidity, dew-point temperature is a measure of the actual moisture content of the air |
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Term
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Definition
an instrument used to commonly used to measure relative humidity
(hygro = moisture, metron = measuring instrument) |
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Term
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Definition
| consists of two identical thermometers mounted side by side; the dry-bulb gives the current air temperature while the wet-bulb measures evaporating air |
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Term
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Definition
| an instrument used to measure relative humidity that operates on the principle that hair or certain synthetic fibers change their length in proportion to changes in the relative humidity, lengthening as relative humidity increases and shrinking as the relative humidity drops |
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Term
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Definition
| contains an electrical conductor coated with a moisture-absorbing chemical |
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Term
| adiabatic temperature changes |
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Definition
| result when air is compressed or allowed to expand. When air is allowed to expand, it cools and when it is compressed, it warms. |
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Term
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Definition
| imaginary volume of air typically considered to be a few hundred cubic meters in volume |
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Term
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Definition
| unsaturated air cools at the constant rate of 10ºC for every 1,000 meters of ascent; descending air is heated 10ºC for every 1,000 meters of descent |
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Term
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Definition
| varies from 5ºC per 1,000 meters for air with a high moisture content to 9ºC per 1,000 meters for dry air |
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Term
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Definition
| air is forced to rise over a mountainous barrier |
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Term
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Definition
| warmer, less dense air is forced over a barrier of cooler, denser air |
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Term
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Definition
| a pileup of horizontal air flow results in upward movement |
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Term
| localized convective lifting |
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Definition
| unequal surface heating causes localized pockets of air to rise because of their buoyancy |
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Term
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Definition
| occurs when air that has reached the leeward side of mountain loses much of its moisture; when the air descends, it warms adiabatically, making condensation and precipitation even less likely |
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Term
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Definition
| occurs when masses of warm and cold air collide |
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Term
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Definition
| storm systems associated with weather-producing fronts that are responsible for producing a high percentage of the precipitation in the middle latitudes |
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Term
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Definition
| resists vertical movement; if an air parcel's temperature is lower than that of the surrounding environment, it will be denser; and if allowed to move freely, it will sink to its original position |
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Term
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Definition
| if the rising air parcel is warmer and less dense than the surrounding air, it will continue to rise until it reaches an altitude where its temperature equals that of its surroundings |
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Term
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Definition
| the temperature of the atmosphere as determined from observations made by radiosondes and aircraft |
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Term
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Definition
| occurs when the environmental lapse rate is less than the wet adiabatic rate |
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Term
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Definition
| occurs when the environmental lapse rate is greater than the dry adiabatic rate |
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Term
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Definition
| occurs when moist air has an environmental lapse rate between the dry and wet adiabatic rates (between 5 and 10ºC per 1,000 meters) |
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Term
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Definition
| tiny bits of particulate matter that serve as surfaces for water-vapor condensation when condensation occurs in the air above the ground |
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Term
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Definition
particles that are good condensation nuclei because they absorb water
(hygro = moisture, scopic = to seek) |
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Term
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Definition
| a form of condensation best described as visible aggregates of minute droplets of water or tiny crystals of ice |
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Term
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Definition
| classified on the basic of form and height |
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Term
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Definition
high, white, and thin that can occur as patches or as delicate veil-like sheets or extended wispy fibers that often have a feathery appearance
(cirrus = curl of hair) |
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Term
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Definition
consist of globular individual cloud masses; they normally exhibit a flat base and have the appearance of rising domes or towers; frequently described as having a cauliflower structure
(cummulus = a pile) |
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Term
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Definition
sheets or layers that cover much or all of the sky; may be minor breaks, but no distinct individual cloud units
(stratum = a layer) |
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Term
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Definition
| normally have bases above 6,000 meters; made up of cirrus, cirrostratus, and cirroculumus |
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Term
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Definition
| generally occupy heights from 2,000 to 6,000 meters; have the prefix alto as part of their name and are altocumulus and altostratus |
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Term
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Definition
| form below 2,000 meters; consist of stratus, stratocumulus, and nimbostratus |
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Term
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Definition
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Term
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Definition
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Term
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Definition
| composed of globular masses that differ from cirrocumulus clouds in that they are larger and denser |
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Term
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Definition
| create a uniform white to grayish sheet covering the sky with the Sun or Moon visible as a bright spot |
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Term
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Definition
| develop a scalloped bottom that appears as long parallel rolls or broken globular patches |
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Term
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Definition
one of the chief precipitation producers
(nimbus = rainy cloud, stratus = cover with a layer) |
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Term
| clouds of vertical development |
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Definition
| when clouds do not fit into any one of the three heigh categories because their bases are in the low height range but they often extend upward into the middle or high altitudes |
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Term
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Definition
| cumulus clouds that grow dramatically due to a trigger of upward movement which creates a towering cloud; may produce rain showers or a thunderstorm |
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Term
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Definition
| a cloud with its base or or very near the ground |
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Term
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Definition
| when warm, moist air moves over a cool surface, which usually creates a blanket of fog |
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Term
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Definition
| forms on cool, clear, calm nights, when Earth's surface cools rapidly by radiation |
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Term
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Definition
| created when relatively humid air moves up a gradually sloping plain or up the steep slopes of a mountain |
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Term
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Definition
| when the saturation of air occurs primarily because of the addition of water vapor; two types are steam fog and frontal fog |
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Term
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Definition
| when cool air moves over warm water and the rising vapor immediately recondenses as it meets the cold air; the water appears to be steaming |
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Term
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Definition
when frontal wedging occurs, warm air is lifted over cold air; if the resulting clouds yield rain and the cold air below is near dew point, enough rain will evaporate to produce fog
also known as precipitation fog |
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Term
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Definition
| the process that generates much of the precipitation in the middle latitudes; relies on supercooling and supersaturation |
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Term
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Definition
| water in the liquid state below 0ºC that will readily freeze if it impacts an object |
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Term
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Definition
| supercooled water droplets will freeze upon contact with solid particles that have a crystal form closely resembling that of ice |
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Term
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Definition
| when the relative humidity of the air is greater than 100% |
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Term
| collision-coalescence process |
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Definition
| copious rainfall can be associated with clouds located well below the freezing level (warm clouds), particularly in the tropics |
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Term
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Definition
| restricted to drops of water that fall from a cloud and have a diameter of at least 0.5 mm |
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Term
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Definition
| most rain originates either in nimbostratus clouds or in towering cumulonimbus clouds that are capable of producing unusually heavy rainfalls |
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Term
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Definition
| fine, uniform drops of water having a diameter of less than 0.5 mm |
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Term
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Definition
| precipitation in the form of ice crystals (snowflakes), or more often, aggregates of crystals |
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Term
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Definition
| a wintertime phenomenon that refers to the fall of small particles of ice that are clear to translucent |
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Term
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Definition
| the subfreezing air near the ground is not thick enough to allow the droplets to freeze but become supercooled as they fall through the cold air and turn to ice upon colliding with solid objects |
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Term
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Definition
| precipitation in the form of hard, rounded pellets or irregular lumps of ice |
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Term
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Definition
| a deposit of ice crystals formed by the freezing of supercooled fog or cloud droplets on objects whose surface temperature is below freezing |
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Term
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Definition
| measures the accumulation of rain and has a diameter of about 20 cm |
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Term
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Definition
| when the amount of rain is less than 0.025 cm |
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