Water in the Atmosphere

Characteristics of Water

• Water is unique because it is commonly found in 3 states of matter

• The form commonly found in the atmosphere is water vapor

Water in the Atmosphere

Ice (snow and frost)

Liquid water(clouds, rain, dew)

Water Vapor(invisible)

Melting

Freezing Condensation

Evaporation

Sublimation

Deposition

What is Specific Humidity?

• Specific humidity is the actual amount of water vapor in the air at any given time and place.

What does it mean if air is saturated?

Air has a maximum capacity of water that it can hold. When it gets to this point, the rate of evaporation is equal to the rate of condensation. This air is saturated, meaning it cannot hold any more water vapor. The warmer the air, the more water vapor it can hold.

What is Relative Humidity?

Relative Humidity is a value that shows how near the air is to its maximum capacity for holding water.

How is Relative Humidity found?

Specific Humidity X 100 = RH %Maximum Capacity

What instrument is used?

A sling psychrometer contains 2 thermometers, a wet-bulb and a dry-bulb. It works on the principle that evaporation is a cooling process.

When does water vapor condense into liquid water?

When air temperature drops, air becomes saturated and condensation begins. The temperature at which this occurs is called the dew point.

How does water vapor condense?

• When there is a surface for the vapor to condense onto.• When the air temperature is below the dew point.

What are condensation nuclei?

Tiny particles that water vapor condenses onto dust, salt, particulate matter.

What can form as a result of condensation of water vapor?

1. Dew - Air cools at night and water vapor condenses on the ground (temp above 0)

2. Frost - Night temps are below 0

3. Fog- Water vapor condenses in the air close to the surface.

4. Clouds - Air above the surface at any altitude in the atmosphere cools below the dew point.

What are the types of clouds?

Clouds are classified based on shape and heightShapesStratus - layered cloudsCumulus - puffy, cotton ball cloudsCirrus - high, feathery cloudsNimbus - rain

HeightsStrato - low level(2,000 m)Alto - middle level (2,000-7,000m)Cirro - high level (above 7,000m)