WHAT INFLUENCES WEATHER?
1. The water table:
a. Evaporation – liquid water
changes into water vapor (warm air
rising)
b. Condensation – water vapor cools
to the dew point, and turns to a liquid
on solid nuclei (salt, smoke, dirt, dust)
c. Precipitation – rain, snow, sleet or
hail fall from clouds
2. Air masses – large volumes of air with the
same temperature and humidity
3. Fronts – forms between 2 air masses
a.Cold front – cold air mass pushes a warm
(less dense)air mass up
In front is stormy weather
Behind is cool dry weather
b. Warm front – a warm air mass (less
dense) slides up and over a cold air mass
In front is rain
Behind is warm humid air
c. Stationary front - warm and cold air
masses meet but not enough wind to
move them
Many days of unchanging weather
4. Pressure systems
a. High pressure - air sinks and
no clouds form - clear skies (Happy
weather)
b. Low pressure – air rising and
forming clouds (Lousy weather)
5. Global winds
*Wind is caused by unequal heating
which creates unequal pressure.
*Cold air near the poles sinks and
causes high pressure.
*Cold air moves toward the equator
(H to L)which is warm and low
pressure.
*Winds bring air masses of different
temperature and moisture content to
a region.
6. Jet stream
• A long distance wind that travels above global
winds.
• Form because of unequal heating of Earth’s
surface.
• Flow in a wavy pattern from west to east.
• Polar jet streams
• Subtropical jet streams
• Can affect temperature and moisture of a region.
• Strong storms tend to forma long jet streams.
7. Ocean currents
• Different winds cause currents to
flow in different directions.
• Energy from warm currents transfers
to colder water changing local
temperature and moisture content.
• Also play a part in hurricanes and
monsoons.
• Cool ocean currents lower coastal air
temperatures.
• Warm ocean currents raise the
coastal air temperatures.