2. Definition: Weather is the state of the atmosphere at a specific time and place. Weather is the result of heat from the sun and earth's air and water.

3. Air Temperature DEFINITION Measure of the amount of heat (average amount of motion, or kinetic energy, of molecules) in the air

4. Air Temperature FACTORS THAT AFFECT Location on Earth- how directly the sun’s rays strike the area Amount of radiation from the sun

5. Air Temperature MESUREMENT Thermometer in degrees Celsius (°C)

6. Air Pressure (Atmospheric Pressure) DEFINITION The force of air exerted on an area from all directions, including directly down, on Earth

7. Air Pressure (Atmospheric Pressure) FACTORS THAT AFFECT Gravity pulling on air Altitude Density of the air – how close the molecules are together Temperature of air – kinetic motion of molecules

8. Air Pressure (Atmospheric Pressure) MEASUREMENT Barometer – average pressure of atmosphere at sea level = 1 bar; unit for reporting air pressure is millibar (1/1000 of a bar)

9. Wind DEFINITION Movement of air from an area of high pressure to an area of low pressure Described by direction and speed

10. Wind FACTORS THAT AFFECT Differences in the amount of solar radiation received Coriolis effect- rotation of the Earth

11. Wind MEASURMENT Wind vane- measures wind direction- arrow points in the direction from which wind is blowing; a compass point may also be used Anemometer- measures wind speed in kilometers (or miles) per hour

12. MOISTURE: DEFINTION Water in the atmosphere; transitions between any of water’s three states in Earth's normal temperature range

13. MOISTURE: FACTORS THAT AFFECT Air Temperature

14. MOISTURE: MEASURMENT Measured as humidity

15. MOISTURE: Humidity DEFINITION Amount of water vapor in the air

16. MOISTURE: Humidity FACTORS THAT EFFECT Air temperature- Heat from the sun evaporates water

17. MOISTURE: Humidity MEASUREMENT Hygrometer– measured in percent

18. MOISTURE: Relative Humidity DEFINITION Amount of water vapor in volume of air compared to the maximum amount the air can hold (saturation) at a given temperature

19. MOISTURE: Relative Humidity FACTORS THAT AFFECT Humidity Air Volume Temperature

20. MOISTURE: Relative Humidity MEASURMENT Psychrometer- measure can range from 0-100 percent

21. MOISTURE: Dew Point DEFINITION Temperature at which air is saturated (holding all the moisture it can hold) and condensation (dew or frost) forms

22. MOISTURE: Dew Point FACTORS THAT EFFECT Humidity Temperature Air Pressure

23. MOISTURE: Dew Point MEASUREMENT Calculated using humidity, temperature, and air pressure

24. MOISTURE: Cloud Formation and Type DEFINITION Warm air forced upwards, expands, and cools; When the air is saturated, water vapor condenses around small particles such as dust or salt

25. MOISTURE: Cloud Formation and Type FACTORS THAT AFFECT Temperature Air Pressure Humidity

26. MOISTURE: Cloud Formation and Type MEASUREMENT Shape and Height: Stratus- smooth layers at low elevation Cumulus- puffy, white Cirrus- High, thin, white, feathery

27. MOISTURE: Precipitation DEFINITION Water falling from clouds

28. MOISTURE: Precipitation FACTORS THAT AFFECT Air Temperature- rain, snow, sleet, hail

29. MOISTURE: Precipitation MEASUREMENT Rain Gauge- Measured in centimeters or inches