• Humidity
–
The measure of the amount of water vapor in the air.
•
Relative Humidity
– The percentage
of water vapor in the air compared to the maximum amount the air could hold.
–
When relative humidity is high, evaporation slows down.
•
Measuring Relative Humidity
– Psychrometer
• Uses a wet bulb
and dry bulb thermometer
• Because
the wet bulb thermometer is cooled by evaporation, its reading drops below that of the dry-bulb thermometer.
• How Clouds Form
– Clouds form through condensation, when
water vapor in the air becomes liquid water or ice crystals.
–
Dew Point: The temperature at which condensation forms.
•
Warm air containing water vapor cools, forcing some of the water out of the air and forming water droplets.
• Particles must be present
for condensation to form.
• Types
of Clouds
– Classified by type and altitude
– 3 main types
•
Cumulus
• Stratus
• Cirrus
–
Cumulus
– Means
“heap” or “mass”
– Indicates
fair weather
– Look
like fluffy piles of cotton
•
Stratus
– Strato
means “spread out”
– Usually
cover all or most of the sky
•
Stratus
– Strato
means “spread out”
– Usually
cover all or most of the sky
– May
thicken to form precipitation (nimbostratus)
•
Cirrus
– Form
only at high altitudes (+6 Km)
– Made
of ice crystals
• Naming
clouds
– May be based on height
– 2 to 6 km above surface = alto meaning
“high”
Clouds close
to the ground are called fog.