Weather. All photos, graphics, and text copyright 2007 Kris Light

Transcription

1 Weather All photos, graphics, and text copyright 2007 Kris Light

2 Weather is a Child of the Sun, Atmosphere, and Water The 3 elements necessary to have weather on earth are: 1. The warmth from the sun to evaporate the water 2. The atmosphere (the blanket of air around the earth), where weather takes place (up to 9 miles high) 3. The water in the lakes, oceans, and ice caps All of the planets in our solar system have weather except Mercury (it doesn t t have an atmosphere).

3 The Water Cycle When the sun shines on the Earth it causes the water to evaporateate (note the word "vapor") and go into the air. If the vapor rises high into the atmosphere, gets cold and then the molecules begin to stick together, condensation occurs and clouds form. If the clouds become saturated and can no longer hold the moisture, precipitation occurs in the form of rain, snow, sleet, freezing rain, or hail. Condensation and precipitation occur on a glass with a cold drink on a humid day, resulting in a water ring on the table. There is a common misconception that the water gets on the side of the glass when the glass "sweats". I explain to my students that in order to sweat, water has to come out of something, (like their armpits!) water doesn't come out of the glass! See diagram on following page

4 The Water Cycle Sun Condensation Cloud Precipitation Evaporation Water Molecules Surface water

5 Above 20,000 feet Basic Cloud Types Cirrus 6,500 23,000 Feet Cumulus Cumulonimbus Stratus Tornado Below 6,500 feet Ground Fog

6 Cirrus means hair curl, these are also called mare s s tails because of their long wispy appearance. Cirrus clouds form in the high atmosphere (>20,000 feet) where the temperatures can be less than -50ºF, they are made up of tiny ice crystals. These clouds do not make rain or snow. They are often the precursors of approaching rain systems. Cirrus Clouds

7 What is a Sundog? A Sundog is an icebow,, formed when sunlight is refracted into the spectrum by the ice crystals of cirrus clouds.

8 Cumulus Clouds Cumulus means piled up,, these are mid-level clouds (6,500 20,000 feet) made up of water droplets. There is not enough water in these clouds to make rain or snow.

9 Stratus Clouds Stratus means sheet- like.. These clouds are low, flat and widespread like the sheets on a bed. These clouds can cover entire states and even regions of the country! They are between 50 6,500 feet in altitude. These clouds can produce rain or snow. Stratus clouds as seen from above

10 Fog in the Grand Canyon Fog on a mountain top Fog Fog is a ground-level cloud (below 50 feet in altitude). It often settles in low areas near water. Fog is common near the ocean. The small water droplets can sometimes be seen on a foggy night if they are lit by a porch light.

11 Cumulonimbus Cloud These piled-up rain clouds can tower to 60,000 feet. Cumulonimbus clouds can produce thunderstorms with torrential rain, downburst winds, lightning, hail, and even tornadoes.

12 Cumulonimbus cloud Thunderstorms are formed by cumulonimbus clouds. It is often possible to watch these clouds billow and grow as the warm air rises within them. These clouds can be sheared off at the top by strong upper-level winds, producing the anvil-head shape. -- Negative Charges - - Hail grows as it rises Uprising Warm Air - Negative Charges - - Sinking Cool Air + Positive Charges ++ + Positive Charges ++ Anvil-head Cold, dry air Tornadoes can form if the air becomes unstable enough and begins to spin within the cloud. Warm, humid air Up to 60,000 feet

13 Lightning Lightning is a powerful bolt of static electricity. It is produced within a cumulonimbus cloud when the electrons are stripped from the water molecules as they are buffeted around by rising and sinking air. The negative and positive charges attract each other, resulting in a visible flash. At 56,000ºF, Lightning is 5x hotter than the surface of the sun. Seek shelter in a car or sturdy building if you see lightning or hear thunder, never stand under a tree or in an open field during a storm. Thunder occurs due to the sudden expansion of air when the temperature changes immediately after a lightning strike.

14 This is why you should not stand under a tree during a thunderstorm! This oak tree was struck by lightning in September 1999.

15 Red Skies and Halos Red Sky at Morning Red Sky at Night There is truth in the old weather poem, Red sky at morning, Sailors take warning. Red sky at night, Sailors delight. The red color comes from the low angle of the sun s light and water vapor in the atmosphere from advancing or retreating weather systems. Red sunrises indicate coming rain or snow; red sunsets indicate the passing of a weather system. A halo around the moon indicates an approaching rain or snow system.

16 When a rain system passes sometimes the sun shines behind it. Sunlight passing through raindrops can be refracted into the colors of the spectrum: red, orange, yellow, green, blue,, indigo and violet.. An easy way to remember the order is: ROY G BIV sunlight Raindrop

17 Types of Precipitation Rain above 32ºF Snow below 32ºF Sleet (Frozen raindrops) Starts out as rain in warmer air, then freezes in colder air layer Freezing Rain (Ice Storm) - Starts out as rain in warmer air, then freezes in colder air layer near the ground Hail Forms only in thunderstorms, the stronger the storm, the larger the hailstones

18 Precipitation Diagram Warm air >32ºF Cold air < 32ºF

19 Snowflakes Snowflakes always have 6 sides or points. Different kinds of snowflakes form in different temperatures. These snowflakes are the dendrite type, they form when the temperature in the clouds is between 3 degrees and 10 degrees. There are also columns, needles and plates.

20 L Air Pressure Systems H Low Pressure systems are made up of warm, moist, rising air. They move in a counter- clockwise direction. They are signified by a L on a weather map. Low pressure systems can bring rain or snow. The lower the pressure reading, the stronger the storm system. High Pressure systems are made up of cold, dry, sinking air. They move in a clockwise direction. They are signified on a weather map by a H. High pressure systems bring cooler, but dry weather. Think: High, Dry and Blue Sky.

21 Wind Wind is moving air produced by change in air pressure, often preceding a dramatic change in weather.

22 Storm Safety When a Storm / Tornado Watch has been issued it means the weather conditions are suitable for a severe storm or tornado to occur. People should listen to the weather radio, TV or watch the sky and be prepared to take cover. When a Storm / Tornado Warning has been issued by the National Weather Service, it means the storm or tornado is occuring. People in the affected area should take cover immediately in the lowest part of their building, preferably away from windows, crouching low next to an inside wall, covering the neck and ears.

23 Tornadoes Tornadoes are short-lived, but violent cyclonic winds. These storms can occur at any time of the year, but usually in the spring, summer and fall. Tornadoes almost always form over land, last less than 30 minutes, and are usually not much larger than a mile wide at the base. Tornado winds are measured by the Fujita Scale from F-1 F 1 to a devastating F-F 5. Dust devils are a type of mini- tornado,, the winds in one can reach speeds up to 60 miles per hour. A dust devil on a soda lake in southern California

24 Hurricanes Hurricanes form only over warm ocean water, usually between June and October. These monster storms can last 2-33 weeks and grow to over 300 miles across. When wind speed reaches 74 miles per hour, the storm is considered a hurricane. The air pressure drops dramatically during a hurricane. Much of the damage from a hurricane is not done by the wind, but the storm surge, a wall of sea water pushed ahead of the storm. It floods low-lying lying areas of the coast, washing away buildings and eroding shorelines. More people die from flooding than being injured by flying debris or falling buildings. The winds in a hurricane can reach over 160 miles per hour. Hurricanes are measured by the Saffir-Simpson Simpson scale from Category 1 to a catastrophic Category 5. Damage in Florida from Hurricane Ivan

25 Follow-up Questions 1. Name the three parts of the water cycle. 2. Name the basic cloud types. Which ones produce rain or snow? 3. How does freezing rain occur? 4. What is the difference between a Low pressure system and a High system? 5. What is the difference between a watch and a warning in weather reporting? 6. Tell the differences between a tornado and a hurricane.

26 End of Presentation Kris Light For more photos and information, go to the Weather gallery at: et_albumname=weather