Weather Unit Notes
Weather Instruments
 Barometer: measures air pressure
 Anemometer: measures wind speed
 Wind Vane: measures wind direction
 Thermometer: measures temperature
 Rain Gauge: measures amount of rainfall
 When collecting data from a rain gauge, you should check and record the data every day at the same
time
Clouds
 Cirrus: wispy, feather- like clouds, high in the sky, fair weather
 Stratus: low, blanket-like clouds, can bring rain showers
 Cumulus: puffy, cotton-like clouds, fair weather
 Cumulonimbus: puffy clouds stacked vertically, cause thunderstorms
 “Nimbus” means PRECIPITATION (rain, snow, sleet, hail)
 Nimbostratus clouds cause steady rain showers
 Hot, dry air means clear skies with few clouds
 Cloud cover decreases temperature
 Heavy cloud cover at night causes temperatures to be warmer because air doesn’t pass through clouds
 There is more cloud cover at higher altitudes because water vapor condenses at cooler temperatures
Temperature
 Daily temperature ranges and precipitation amounts are used in recording seasonal climate
 Global warming causes temperatures to increase
 Large bodies of water that are near land cause the weather to be warmer in the winter
 The Gulf Stream usually brings increased temperatures to NC
 Tropical Air masses cause an increase in temperature
 When a warm air mass replaces a cold air mass the temperature gets warmer
 The temperatures vary during the different seasons in NC
 Water gains and loses heat more slowly than land which causes land temperatures to be more milder
Pressure Systems
 HIGH pressure system: cool, dry air, sunny/clear weather
 LOW pressure system: thunderstorms
 As air pressure drops throughout the day, the weather will become cloudy with a chance of rain
 As air pressure decreases, temperature decreases
 Differences in air pressure cause greater wind speeds
 When HIGH pressure and LOW pressure systems meet, precipitation usually happens
Storms
 Hurricanes form in the ocean near warm areas
 Warm water temperatures and a tropical storm moving from the southeast will create a Hurricane off the
coast of NC
 Ice crystals that form over and over during thunderstorms are called Hail
Winds
 Wind is caused by the uneven heating of Earth
 Weather conditions in NC are caused by prevailing winds that move WEST to EAST
 Westerly winds moving across deserts bring hot, dry weather to NC
 Prevailing westerly winds cold weather to NC in the winter
 The rotation of the earth determines the direction in which air masses flow
 Global winds blow WEST to EAST
 Sea breezes form because land warms up faster than cool ocean waters
 Air that is constantly moving because of the differences in water temperature and land temperature
cause sea breezes
Jet Stream
 The jet stream brings cold arctic air in the winter months
 The jet stream is responsible for the movement of different air masses
 Winds in the jet stream blow between a boundary of cold air and a boundary of hot air
Other Important Weather Information
 Scientists collect data about the water vapor in the air to determine the humidity level
 If you want to determine the climate of an area you should get information from the local weather
station records from the last few years
 To determine drought conditions scientists measure rainfall and lake and river water levels
 Continental polar winds are responsible for cold weather that occurs in NC during the winter
 At the equator, warmer conditions create an increase in evaporation. Evaporation leads to more
precipitation
 Unequal heating of Earth causes Global Atmospheric patterns