1. Topic VI “Meteorology”
Weather Studies

2. I. Moisture in the Atmosphere: the primary source of energy for the water cycle is the Sun. It unevenly heats Earth’s surface.
A. Phases of the Water Cycle:
1. Evaporation: liquid to gas. Requires energy making it a cooling process.
2. Condensation: gas (water vapor) to a liquid. Releases energy into the air.

3. 3. Transpiration: the releasing of water in the air by plants.
4. Precipitation: the falling of liquid or solid water from clouds.
Ex. Rain, sleet, snow and hail.

4. B. Factors Affecting Evaporation Rate:
1. Temp.: as temp. inc. evap. rate inc.
2. Humidity: as humidity inc. evap. rate decreases.
3. Wind: as wind inc. evap. rate inc.
4. Surface Area: as surface area inc. evap. rate increases.

5. C. Relative Humidity: a comparison between the amount of moisture in the air with the amount that the air can hold at that temp.
Dewpoint Temp.: the temp. at which condensation occurs.
* dew: drops of water forming on a cool surface.
* frost: water vapor freezes (sublimates) on a frozen surface.

6. 2. Sling Psychrometer: instrument used to determine the dewpoint temp
2. Sling Psychrometer: instrument used to determine the dewpoint temp. and relative humidity.
3. Steps to determine Dewpoint:
a. Find dry bulb temp.
b. Find the diff. Between the wet and dry bulb temps.
c. Use the chart on page 12 of the ref. Table.

7. D. Clouds: collection of tiny water droplets or ice crystals suspended in the atmosphere.
1. Cloud Formation:
a. Warm moist air rises.
b. Air cools below dewpoint temp. and droplets form around condensation nuclei (dust/salts).

8. 2. Cloud Types:
a. Cumulus: big puffy white clouds.
b. Cirrus: whispy ice crystals high in the atmosphere.
c. Stratus: low clouds that blanket the sky.

9. II. Air Pressure: the force/weight of air pushing on a surface
II. Air Pressure: the force/weight of air pushing on a surface. Air pressure pushes in all directions equally. Pg. 13 ref. Table.
A. Barometer: instrument used to measure air pressure.
* As air pressure increases, the barometer rises.

10. B. Factors Affecting Air Pressure:
1. Temperature: as temp. increases, air pressure decreases.
2. Altitude: as altitude increases, air pressure decreases.
3. Humidity: as humidity increases, air pressure decreases.

11. C. Winds: caused by differences in air pressure
C. Winds: caused by differences in air pressure. The greater the difference (gradient) the stronger the winds.
1. Isobars: connect points of equal air pressure.
*the closer the isobars the stronger the winds.

12. D. Local Breezes: smaller horizontal movement of air .
1. Sea breeze: air flows from the sea to the land.
*cooler air (high pressure) over the sea, flows towards warmer air (low pressure) over the land.

13. 2. Land breeze: air flows from the land to the sea.
* Air over the land cools at night and flows towards the warmer air over the water.

14. E. Wind Direction: flow from regions of high to low pressure and named for the direction they come from.
1. Cyclone: (low pressure) winds blow counterclockwise towards the middle.
2. Anticyclone: (high pressure) winds blow clockwise and out.

15. F. Global Winds: caused by the unequal heating of earth’s surface
F. Global Winds: caused by the unequal heating of earth’s surface. Page 14 ref. Table.
1. Diverging zones: cool, dry high pressure air sinks at the poles and 300 lat.
2. Converging zones: warm, moist low pressure air rises at the equator and 600 lat.

16. III. Air Masses: large masses of air that have a characteristic temp
III. Air Masses: large masses of air that have a characteristic temp. and moisture of their source region. Page 13 ref. table.
A. Source Regions:
1. Maritime: formed over water. (moist)
2. Continental: formed over land. (dry)
3. Polar: cool air from high latitudes
4. Tropical: warm air from low latitudes.

17. IV. Front: the boundary that separates two different air masses. Pg
IV. Front: the boundary that separates two different air masses. Pg. 13 ref.
A. Types of Fronts:
1. Cold Front: dense cold air forces warm moist air upward creating heavy precipitation for short periods of time at the frontal boundary.

18. 2. Warm Front: warm air slowly rises over cold air producing long periods of light precipitation ahead of the frontal boundary.

19. 3. Occluded Front: a fast moving cold front over takes a slower warm front causing clouds and precipitation.

20. 4. Stationary Front: cold and warm air masses near each other with neither advancing causing long periods of light precipitation.

21. B. Synoptic Weather Maps: show weather conditions on a national or global basis.
1. Storm Tracks: most storm systems move from west to east across the U.S.

22. V. Severe Weather:
A. Hurricanes: a large rotating storm of tropical origin.
*they get their energy from warm water. Once they hit land they lose energy.

23. Hurricane Eye

24. B Tornadoes: caused by the collision of warm, moist air with cold, dry air. Winds can exceed 370 mph.
C. Storm Safety:
1. Stay indoors
2. Store food/water
3. Have batteries/flashlights
4. Have a radio