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25 terms

Unit 5.2

STUDY
PLAY
Latent heat
the heat energy absorbed or released by a substance during a phase change; example: when liquid water evaporates, the water absorbs energy from the environment, which becomes potential energy between the molecules; when wter vapor changes back into a liquid through the process of condensation, the energy is released to the surrounding air
Humidity
the amount of water vapor in the air; when water evaporates, the humidity of the air is increasing; as the temperature of the air increases, the air's ability to hold water vapor also increases; recall, warm air holds more water vapor than cool air
Absolute Humidity
the mass of water vapor contained in a given volume of air; a measure of the actual amount of water vapor in the air; however, as air moves, its volume changes as a result of temperature and pressure changes
Relative Humidity
a ratio of the actual water vapor content of the air to the amount of water vapor needed to reach saturation; a more common way to measure humidity; calculated by using the following formula: relative humidity (RH) %= actual water vapor content (g/kg)/saturation water vapor content (g/kg) *100
Relative Humidity is affected by
amount of water vapor-- at constant temperature and pressure, the more water vapor there is in the air, the higher the relative humidity; and temperature-- at constant water vapor content in the air, increased temperature leads to lower relative humidity adn decreased temperature leads to higher
psychrometer
an instrument used to measure relative humidity made of two thermometers; dry-bulb and wet-bulb (covered iwth a damp cloth); the difference between the readings indicates the amount of water vapor in the air; the larger the difference, the less water vapor in the air, therefore lower humidity; the smaller the difference, the more water vapor in the air, therefore higher humidity
dew point
the temperature a gas condenses into a liquid
Condensation
the process by which a gas, such as water vapor, becomes a liquid; before this can occur, the air must be saturated RH of 100%; air can become saturated: when water vapor is added through evaporation and when air cools to the dew point, which is the temperature a gas condenses into a liquid
Cloud
a collection of small water droplets or ice crystals in teh air; form as warm air rises and cools, condenses onto tiny particles of gas and dust in the atmosphere; classified based on shape and altitude; for water vapor to condense and forma cloud, a solid surface on which condensatino can take place must be available; the troposphere containts millions of particles of ice, salt, dust, smoke, and other particles serving as solid surfaces
Condensation nuclei
these suspended particles providing a surface necessary for water vapor to condense
Stratus Clouds
clouds are clouds forming in layers and have a flat, uniform base beginning to form at low altitudes; cover large areas of the sky and often block out the sun; form where a lyer of warm, moist air lies above a layer of cool air; overlying warm air cools to the dew point, creating a cloud
Nimbo/nimbus
means rain; nimbostratus clouds are dark stratus clouds usually producing heavy, continuous rainfall
Cumulus clouds
puffy, white clouds tending to have flat bottoms; form when warm, moist air rises and cools; normally indicate fair weather; if they get larger, they can produce thunderstorms-- cumulonimbus clouds
Cirrus clouds
thin, feathery clouds found at high altitudes; made of ice crystals due to low temperatures at higher altitudes in the troposphere; form as a result of strong winds; if they get thicker, cirrus clouds indicate a change in weather is coming
Cirro-
used to describe clouds forming at higher altitudes; normally made of ice crystals
Alto-
used to describe clouds forming at middle altitudes; can be made of both water droplets and ice crystals
Fog
water vapor that has condensed very near the surface of the Earth because air close to the ground has cooled
Radiation fog
a type of fog formed from teh nightly cooling of Earth; layer of air in contact with the ground becomes chilled to below the dew point
Advection fog
forms when warm, moist air moves across a cold surface; common along coasts
Precipitation
when water from the air (condensed clouds) returns to the Earth's surface
Rain
most common; begins as a drop smaller than a period at the end of a sentence
Snow
forms when temperatures are so cold, water vapor changes directly to solid and falls to the ground as a single crystal or snowflake
Sleet
forms when rain falls through a layer of freezing air; the rain freezes in the air, producing falling ice
Freezing rain
occurs when cold water droplets freeze when they make contact with Earth's surface
Hail
balls or lumps of ice falling directly from clouds; forms in cumulonimbus clouds; common during thunderstorms and tornadoes