Download Weather Notes

Weather:
 the present state of the atmosphere and the
current conditions
 Factors that effect the weather: air pressure,
wind, temperature, and humidity.
Humidity
 - the amount of water vapor in the air.
 solar energy evaporates water creating water
vapor in the atmosphere
 more vapor is present at warm temperatures
than at cold temperatures
 this is because the space between molecules
expands as the air warms up, but is smaller
as it cools
Relative Humidity
 - the amount of water vapor in the air
compared to the amount it could hold
at a specific temperature

-weather forecasters share
humidity as this

-ex: if it is 50% humidity, that
means the air is holding 50% of water
vapor it could hold at that temperature
Saturated-
Dew Point
 when the air holds
 the temperature at
which water vapor in
as much water vapor
as possible, or 100%
humidity.
the air will condense
and turn back to
liquid.
- form from warm moist air rising in the
atmosphere
-as they rise the water vapor cools and
condenses into tiny water drops
-these drops form around small particles of
dust, salt, and smoke in the atmosphere
-when millions of these drops collect
together, a cloud is formed
Cloud Types- classified by shape
and altitude
 stratus

-form layers or smooth sheets in the sky

-usually at low altitudes

-usually fair (good) weather or precipitation
(rain)

-can form near the ground called FOG
cumulus
 -puffy white clouds with flat bottoms
 -form when air currents rise up
 -can rise to high altitudes
 -usually fair weather or thunderstorms
-cirrus
high, thin, white, feathery clouds
-high altitudes
-contain ice crystals
-indicate fair weather, but may
indicate approaching storms
nimbus
-dark clouds
-associated with precipitation
-dark because they are so full of
water vapor, no light penetrates
cumulonimbus
 towering thunder clouds
 -caused by warm and cold fronts colliding
 -precipitation is heavy rains and hail
Precipitation
 Rain- formed by saturated air that condenses to form rain

 Sleet- formed by snow passing through warm air and
melts, then refreezes near the ground

 Snow- formed when water vapor condenses in very cold air
and changes directly to a solid

 Hail-formed in thunderstorms when drops of water
continue to freeze in layers around a small nucleus of ice