1. Weather

2. What is weather? The condition of the air (or atmosphere) at a given location at a give time

3. Climate “Typical” weather in region; the average weather or the regular variations in weather in a region over a period of years includes temperature, air pressure, humidity, days of sunshine, etc... drastically affected by water & mountains –coastlines have cooler summers and warmer winters –mountains greatly slow down winds and weather

4. Atmosphere Blanket of air surrounding the earth Air – the mixture of gases, mainly nitrogen and oxygen, that forms the Earth’s atmosphere 78% Nitrogen 21% Oxygen 1% Argon 1% Other stuff : Carbon dioxide, water vapor, ozone, dust, ash, smoke, etc.

5. Structure of the Atmosphere

6. Lower Layers Troposphere – the layer of the atmosphere that is closest to the earth’s surface, where all weather phenomenon occurs. 8 km thick at the poles 16 km thick at the equator; (air temperature normally decreases with height) Stratosphere - upper layer of air 8 - 16 km to about 50 km and top of the stratosphere contains the ozone layer; almost completely free of clouds.

8. Middle and Upper layers Mesosphere – the layer of air, 50km to 80km where temperature begins to decrease with height, mainly because ozone in the stratosphere absorbs energy from the sun, principally ultraviolet radiation Thermosphere - where air temperatures can exceed 1000° C (1800° F), 80km to 9600 km, primarily due to oxygen absorbing the sun’s energetic rays

10. Upper-Upper layers Ionosphere – the region within the atmosphere containing ionized molecules, layers of ionized air in the atmosphere extending from almost 60 km above the surface of the earth to altitudes of 1000 km and more. Exosphere - The region beyond the thermosphere, which extends to about 9,600 km, the outer limit of the atmosphere.

13. Conditions of the Air Temperature – amount of hotness or coldness relative to something else Thermometer – an instrument that measures relative hotness or coldness Dew Point temperature – The temperature at which air becomes saturated Temperature scales: 1°C = 1.8°F or 1°F = 5/9 ° C

14. Heat transfer Conduction – the movement of heat from molecule to molecule Convection – the movement of heat by warm and cold currents Radiation – the release and transfer of energy in wavelengths of heat and light

15. How is the atmosphere is heated?

17. Pressure Air pressure - the downward pressure exerted by the weight of the overlying atmosphere or the “weight” of the atmosphere per unit AREA. Barometer – an instrument used to measure air pressure Measured in inches of mercury in a column Or millibars (metric conversion) Average air pressure at sea level is 1013 millibars

18. Water in the atmosphere Water Vapor Humidity – the amount of water vapor in the air Relative humidity – the actual amount of water vapor in the air compared to the greatest amount the air can hold

19. Water in the atmosphere Water Vapor Saturated – to be completely filled with water vapor Psychrometer – an instrument to measure relative humidity Hygrometer – an instrument used to measure the air’s humidity

20. Precipitation water or ice that condenses in the air and falls to the ground as: Rain- liquid water that falls to the ground Snow - ice crystal flakes; water vapor in the atmosphere that froze into ice crystals and falls to the ground in the form of flakes Sleet -partially melted grains of ice Hail - pellets made of layers of ice and snow Freezing rain –rain that freezes into ice as it hits the ground

21. Evaporation the process of changing from liquid to gas; molecules in a liquid state GAIN energy to change into a gaseous state (latent heat energy is the stored in molecules through evaporation) Evaporation DRIVES the water cycle

22. Condensation the process of changing from gas to liquid; molecules in a gaseous state that LOOSE energy to change into a liquid state.

24. Clouds a visible mass of dense water vapor or ice suspended in the atmosphere; formed by surface heating & convection and/or warm air lifted by rising over mountains

27. Wind air moving at a speed fast enough to be noticed; high pressure moves to low pressure Weather Vane – an instrument that measures wind direction Anemometer – an instrument that measures wind speed

29. Air Mass A large region of air with similar properties throughout (ie. temperature, humidity)

31. Major Air Masses cA – Continental Artic – dry, very cold cP – Continental Polar – dry and cold cT – Continental Tropical – dry and warm mP – Maritime Polar – moist and cold mT – Maritime Tropical – moist and warm

40. Synoptic Map Station models – group of symbols depicting weather conditions Isobar – line of equal pressure a. show locations of High or Low pressures b. close lines mean strong winds c. lines far apart mean gentle winds

41. Station Model how meteorologists can put a lot of information in a small area

45. Water in the atmosphere Water Vapor Humidity – the amount of water vapor in the air Relative humidity – the actual amount of water vapor in the air compared to the greatest amount the air can hold

46. Weather Advisories Weather WATCH – predictions about approaching severe weather Weather WARNING – specific severe weather conditions have been actually observed by a person or verified by a computer