# Unit 5.2

### 25 terms by Lnarnold24

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### 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

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

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

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