Geography chapter 4 Water in the Atmosphere terms

Evaporation

Change in the state of water from liquid to a gas (water vapor)

Transpiration

Change in the state of water to vapor through plants exhaling water vapor during photosynthesis

Groundwater

Water in the Earth’s crust

Precipitation

Solid / liquid water falling from the atmosphere to the ground

Evaportranspiration

Transpiration and evaporation as a single process that moves water into the atmosphere

Cohesion

Water molecules joining together with Hydrogen bonds

Adhesion

Water molecultes joining to other surfaces

Water molecule lattice formation

Every water molecule is locked with its neighbor with hydrogren bonds

Sensible heat

The calories added to increase the temperature of water

Latent heat

The calories absorbed by water that allow it to change the shape without increasing the temperature

Latent heat of melting

The energy added to ice to melt it but not change its temperature

Latent heat of condensation

The energy released when water vapor condenses back into liquid

Latent heat of vaporization

The energy used to vaporize liquid water into water vapor

Latent heat of freezing

The energy removed from water to turn it into solid ice

Updrafts

Rising columns of air inside clouds created by latent heat

Humidity

The water vapor content of the air

Advect

To carry away

Apparent temperature

What the temperature FEELS like to a person, not what it actually is

Net evaporation

When there is more evaporation than condensation, air is cloud free

Net condensation

When there is more condensation than evaporation, clouds form. Can only occur when air becomes saturated.

Sublimation

When solid water turns directly into water vapor

Deposition

When water vapor turns directly into solid water

Air saturation

The point at which air’s water vapor content is equal to or more than the water vapor capacity of the air

Hygrometer

A tool that measures water vapor in the atmosphere

Sling psychrometer

A large, handheld tool that measures humidity using thermometers

Vapor pressure (VP)

The portion of air pressure exerted exclusively by molecules of water vapor

(weight of atmosphere exerts 1kg of pressure per cm2 of all object at sea level)

A millabar (mb)

A measure of atmospheric pressure that is conceptually identical to kg/cm2

1 mb = 1 hectopascal (hPa) ← metric unit

Saturation vapor pressure (SVP)

The vapor pressure at which saturation occurs

Indicates how close the air is to saturation at any temperature

For every 10C increase in air temperature, the saturation pressure doubles

Specific humidity (SH)

The water vapor content of the atmosphere

Specific humidity = mass of water vapor (g) / mass of the air sample (kg)

Saturation specific humidity

The maximum specific humidity possible

Relative humidity (RH)

The ratio of water vapor content to water vapor capacity expressed as a %

Warmer air can hold more water vapor

Higher relative humidity = closer to saturation

Higher relative humidity = lower temperature, lower RH = higher temperature (inversely related)

RH = (vapor pressure (mb) / saturation vapor pressure (mb) ) * 100%

Dew point (DP)

The point at which air becomes saturated and condensate forms

Air saturated = dew point reached

Dew point depression

The difference between the air temperature and the dew point

Bigger DP depression = more air needs to be cooled to reach saturation

Adiabatic temperature changes

Temperature changes in air parcels caused by changes in their volume

Adiabatic cooling

The cooling of an air parcel through volume expansion

Adiabatic warming

The warming of an air parcel through volume compression

Dry adiabatic lapse rate (DALR)

The rate of temperature change in an unsaturated air parcel

~ 10C / 1000m

The environmental lapse rate

The decrease in air temperature outside the air parcel as altitude increases

Avg environmental lapse rate = 6.5C / 1000m (varies for any location at any time)

Lifting condensation level (LCL)

The altitude at which the temperature inside the air parcel reaches the dew point

Occurs at a constant altitude above the Earth’s surface

Moist adiabatic lapse rate (MALR)

The rate of cooling in a saturated air parcel (usually 6C/1000m)

Is always less than the dry adiabatic rate (10C/1000m) because of the latent heat of condensation.

How much less depends on how much condensation occurs in the cloud so how much latent heat is released.

Stable atmosphere

The interior of the air parcel is cooler and more dense than the surrounding air and the air parcel cannot rise on its own

Must go over a mountain range or a cold mass of dense air

Unstable atmosphere

The interior of the air parcel is warmer and less dense than the surrounding air and can rise on their own

With enough water vapor they can form cloud and thunderstorms

Conditionally unstable atmosphere

Occurs when the environment lapse rate is between the dry rate of cooling and the moist rate of cooling

Air parcel is warmer than the surrounding air

Frost point

Crystals of ice formed by deposition when the dew point is at or below freezing

A rain shadow

A dry environment formed by adiabatic warming on the leeward side of a mountain (side blocked from the wind)

Air parcel

A body of air with uniform humidity and temperature

Convective uplift

Unstable rising air parcels formed by the uneven warming of the atmosphere by the Earth’s surface

Typically forms Cumulus clouds which produce convective precipitation

The adiabatic process

As a warm air parcel rises, the decreasing pressure in the atmosphere allows it to expand. Expansion uses energy, which lowers the internal temperature of the air parcel.

As the air parcel cools, it compresses, increasing its internal temperature.

Orographic uplift

The lifting of air over mountains. Forms orographic clouds.

Orographic clouds

Clouds formed by air moving up the windward side of mountains. Produces orographic precipitation and forms a rain shadow on the leeward side of the mountain.

Can occur anywhere with mountains.

Frontal updrift

Warm and cold air masses meeting at midaltitudes which form a transition zone between cold polar air and warm subtropical air.

The warm air moves over the cold air (frontal updrift). Produces frontal precipitation at mid or high altitudes

Air masses

Geographically extensive and homogenous regions of air

Convergent uplift

When air rises due to surface winds converging in a geographical region of low atmospheric pressure