CHAPTER 3: MOISTURE, CLOUDS, & PRECIPITATION

Calories

Latent Heat

Stored or hidden heat that is not derived from temperature change. Important in atmospheric processes.

Evaporation

A process where liquid is changed to gas.

Condensation

A process where gas (water vapor) is changed to a liquid.

~ Heat energy is released

Melting

A process where a solid is changed to a liquid.

Freezing

A process where liquid is changed to a solid.

~ Heat is released

Sublimation

A process where a solid is changed directly to a gas.

~ EX: ice cubes shrinking in a freezer

Deposition

A process where gas (water vapor) is changed to a solid.

~ Heat is released

~ EX: frost in a freezer compartment

Relative Humidity

The ratio of the air’s actual water vapor content compared with the amount of water vapor required for saturation at that temperature (and pressure).

~ Expressed as a percent %

Dew Point Temperature

The temperature to which a parcel of air would need to be cooled to reach saturation.

Adiabatic Cooling

Adiabetic Heating

Orographic Lifting

Elevated terrains acting as barriers.

• (EX: Mountains)

Frontal Wedging

Cool air acting as a barrier to warm air.

Convergence 

Where the air is flowing together and rises (low pressure).

• (EX: Rains in Florida almost everyday bc of this)

-

Localized Convective Heating

Occurs where unequal surface heating causes pockets of air to rise because of their buoyancy.

Stable Atmosphere

Often results in widespread clouds with little vertical thickness

• Precipitation (if any) is light to moderate

• Resists vertical displacement

• Cooler & denser than surrounding air

Atmospheric Instability

Acts like a hot air balloon - rising air.

• Warmer, but less dense than surrounding air

• Rises until an altitude with the same temp is reached

Condensation Nuclei

Tiny bits of particulate matter that are possible condensation surfaces in the atmosphere.

• (EX: Dust & smoke)

Cumulonimbus

Bergeron Process 

Formation of precipitation where the temperature in a cloud is below freezing.

• Ice crystals collect water vapor

• Large snowflakes form and fall to the ground OR melt during descent and fall as rain

Collision-coalescence Process

Rain

Droplets have at least a 0.5mm diameter - form of precipitation.

Drizzle

Droplets have less than a 0.5mm diameter - form of precipitation.

Snow

Ice crystals / aggregates of ice crystals.

Sleet

Small particles of ice - wintertime phenomenon.

Glaze

Freezing rain - impact with a solid causes freezing.

Hail

Rime

Special kind of frost - longer ice crystals.

• Forms on cold surfaces

➢ How does water change states?

Heat must be absorbed or released.

➢ What is latent heat?

➢ How is humidity measured?

1. Psychrometer

2. Hair Hygrometer

➢ Things that control humidity in the air:

Adding or subtracting moisture in the air.

1. Humidifier: raises humidity

2. Dehumidifier: lowers humidity

➢ What happens at the dew point temperature?

Condensation occurs when air is cooled below this point.

➢ How do adiabatic changes affect temperature?

➢ Difference between wet & dry adiabatic rates:

➢ What are the four ways that air is vertically lifted?

➢ Stable vs. Unstable atmospheric conditions: 

➢ The two main ways clouds form:

➢ Differences in the type of precipitation:

➢ How is precipitation measured?

➢ Different methods of weather modification: