Weather
Chapter 15
What is Weather
Section 15.1
Factors of Weather
Weather present state of the atmosphere
Factors of Weather
Air pressure
Wind
Temperature
Amount of moisture (humidity)
Humidity
Amount of water vapor in the air.
Humidity
Amount of water vapor air can hold depends on temperature.
Temp. increase saturation value increases
Temp. decreases saturation value decreases
Relative Humidity
Amount of water vapor in the air compared to how much it can hold at that temperature.
Relative Humidity
Amount of water vapor contained by air compared to the amount of water vapor the air could hold at
Relative Humidity
RH = absolute humidity divided by saturation value X 100%
Absolute humidity mass of water in one cubic meter of air
Saturation value mass of water air could have in a cubic meter of air at that temperature
Dew Point
Temperature at which dew will form
Temperature at which the air would be at 100% Relative Humidity
Dew point decreases as humidity increases
Cloud Formation
Warm, moist air rises, expands and cools to the dew point
Cloud Formation
Needed for clouds to form
Temperature = dew point
Condensation nuclei
Cloud Classification
Cirro - high
Alto middle
Strato layered
Cumulo puffy
Nimbo - rain
Cloud Formation
Horizontally developed Stratiform
Vertically developed - cumuliform
Horizontally developed
High
Cirrus
Cirrocumulus
Cirrostratus
Middle
Altocumulus
altostratus
Horizontally developed (cont.)
Low
Stratocumulus
Stratus
Nimbostratus
Vertically developed
Cumulus
Cumulonimbus
Types of Precipitation
Rain
Snow
Sleet
Glazed ice
Hail
Drizzle
Weather Patterns
Section 15.2
Air Masses
Large body of air
Same temperature
Same humidity
Air Masses
Land dry continental - c
Ocean humid maritime - m
Poles cool polar - P
Tropics warm tropical - T
Air Masses
cP continental polar dry, cold
cT continental tropical dry, warm
mP maritime polar humid, cold
mT maritime Tropical humid, warm
Air Masses Affecting the US
Polar Atlantic mP
Tropical Atlantic mT
Polar Pacific mP
Tropical Pacific mT
Tropical Gulf mT
Continental Polar - cP
Continental Tropical - cT
Fronts
Boundary between two different Air Masses
Types of Fronts
Cold front cold air pushes back warm air
Warm front warm air pushes back cold air
Stationary front neither air mass moves
Occluded front a faster moving cold front over takes a slower moving warm front
Types of Fronts
Cold front Thunder storms
Warm front long periods of precipitation
Stationary front long periods of precipitation
Occluded front sever weather
Forecasting Weather
Section 15.3
What is a meteorologist?
What is a meteorologist?
Meteorologist studies weather
What is a station model?
What is a station model?
Station model symbols that represent weather measurements on a weather map
Give some station model symbols
Give some station model symbols
Cloud cover
Wind speed
Wind direction
Temperature
Dew point
Barometric pressure
What is an isobar and isotherm?
What is an isobar and isotherm?
Isobar line of equal air pressure on a weather map
Isotherm line of equal temperature on a weather map
How can isobars be used to tell wind speed on a weather map?
Closely spaced isobars high wind speed
Widely spaced isobars low wind speed
How can isobars be used to tell where high and low pressures are located?
Closed isobars with higher high pressure
pressures in the center
Closed isobars with lower low pressure
pressures in the center
Changing the Weather
Section 15.4
Describe human activities that alter the weather.
Describe human activities that alter the weather.
Cloud seeding adding silver iodide or dry ice to clouds to encourage precipitation
Cloud seeding may help prevent violent storms
Describe human activities that alter the weather.
Microclimates are produced by large cities.
