1. 10.2 Earth’s Weather
Mr. Perez

2. Important Vocabulary Condensation Weather Humidity Dew point
Relative humidity
Precipitation

3. Weather Factors
Weather: describes the current condition of the atmosphere
Factors include:
Temperature
Cloud cover
Wind speed
Wind direction
Humidity
Air pressure

4. Temperature Remember, the Sun’s radiant energy powers the water cycle
Most of the energy on the Earth comes from the Sun
Temperature: is a measure of how fast air molecules are moving
If the molecules are moving fast, the temperature is high
If the molecules are moving slowly, the temperature is low

5. Temperature

6. How do we measure temperature?
Temperature can be measured using a thermometer.
There are many units to use to measure temperature:
Celsius
Fahrenheit
Kelvin

7. Heat Transfer
Remember, heat moves from warm objects to cooler objects.
The particles in a warm object transfer energy to the slower moving particles in a cooler object when they bump together.
Conduction: heat moves through objects that are in contact with one another
Convection: heat rises, cold air sinks
Radiation: heat travels through waves

8. Heat Transfer

9. Atmospheric Pressure
Air is made up of particles…because of gravity, air also has a weight.
The weight of air causes it to exert pressure.
We can measure atmospheric pressure using a barometer.
The higher you go, the less pressure there is in the air.
Temperature and pressure are related:
Rising air (warm) means low pressure
Sinking air (cold) means high pressure

10. Atmospheric Pressure

11. Humidity The amount of water vapor in the air is called humidity
Warmer air allows more water to be stored as water vapor in the atmosphere
The dew point is the temperature at which the air is holding as much water vapor as it can (saturated) and condensation can occur
A hygrometer is used to measure humidity

12. Humidity

13. Relative Humidity
Relative humidity is a measure (in percent %) of the amount of water vapor that is present compared to the amount that could be held at a specific temperature
When air is saturated it has 100% relative humidity
For example, in the previous chart air at 40°C can hold 50 g/cm3 when saturated. If it only has 25 g/cm3, the relative humidity is 50%.

14. Dew Point & Relative Humidity
If the dew point is close to the air temperature the relative humidity is high
If the dew point is much lower than the air temperature, the relative humidity is low

15. Clouds
Clouds form when air rises, cools to its dew point, and becomes saturated (basically condensation)
In order to form a cloud, the water vapor must have something to stick to
If the temperature is cold enough, the cloud will be made of ice crystals. If not cold enough, water droplets make up the cloud.

16. Cloud Classification Group Altitude Cloud names Cloud descriptions LOW
MIDDLE
HIGH
VERTICAL

17. LOW CLOUDS LOW GROUP: 2,000 meters or less
Cumulus- puffy clouds formed when air currents rise, carrying moisture with them.
Stratus- form dull, gray sheets that can cover the entire sky with layers of cloud
Nimbostratus- low, dark, thick layers that blot out the sun

18. MIDDLE CLOUDS MIDDLE GROUP: 2,000 – 8,000 meters
Altocumulus- layered and wispy, can produce light precipitation
Altostratus- layered and puffy, can produce light precipitation

19. HIGH CLOUDS HIGH GROUP: 8,000 meters or more
Cirrus- wispy, high level clouds
Cirrostratus- high, layered clouds that sometimes cover the sky

20. VERTICAL CLOUDS
VERTICAL GROUP: spans through several different group layers
Cumulonimbus- create the heaviest precipitation of all; known as thunderstorm clouds
TIP: Nimbus in the name of a cloud usually means they form precipitation

22. Precipitation
When ice crystals or water vapor become too large to be suspended by clouds, they fall as precipitation
Forms include:
Rain
Freezing rain
Hail
Sleet
Snow

23. Wind Air moves from high pressure areas to low pressure areas
The greater the difference in temperature or pressure between two areas, the stronger the winds will blow between them
Wind speed is measure with a tool called an anemometer

24. Global Air Circulation
The Earth’s tropical area near the equator heat up more than the Poles of the Earth.
Warm air flows towards the poles from the equator and cold air flows towards the equator from the poles
Earth’s rotation causes the winds in the Northern Hemisphere to deflect to the right and in the Southern Hemisphere to the left. (Coriolis Effect)

25. Coriolis Effect

26. Surface Winds
Trade winds (Tropical Easterlies) blow East to West between the equator and 30°
Prevailing westerlies blow from the west between 30° and 60°
Polar easterlies blow from the east between 60° and the poles

27. Jet Streams
Jet streams are bands of strong wind that develop at high altitudes within the zone of prevailing westerlies.
Weather systems move along jet streams.

28. Other Winds
Besides the major winds, there are other winds constantly forming
Tornadoes and hurricanes are formed when air rushes into the center of a low pressure system.

29. Weather Instruments Anemometer to measure wind
Hygrometer to measure humidity
Barometer to measure atmospheric pressure
Thermometer to measure temperature

30. Closing Questions PAGE 303 # 1-5
In your notes, answer the following questions in the RED textbook
PAGE 303 # 1-5
You do not have to write the question, only complete answers.

31. References
Florida Science Grade 6, Glencoe Science & McGraw Hill Publishing
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