DOPPLER EFFECT • Refers to the change in frequency when there is relative motion between an observer of waves and the source of the waves • Doppler with Sound
The Doppler effect- Change in frequency due to the source or receiver greater the speed the source, greater the Doppler effect Stationary bug Bug swimming
What Christian Doppler predicted, and the observer confirmed, was that the frequency (pitch) of the source (the whistle) increased or rose as the train approached and decreased or fell as it moved away.
More than 50 years later, Albert Einstein demonstrated that this phenomenon, called the Doppler Effect, was also true for electromagnetic waves.
Meteorologists, as well as astronomers and other physical scientists, use the color blue or violet to indicate movement toward the radar and the color red to indicate movement away from the radar. The Doppler Radar Worksheet provides the pattern of Doppler velocities that covers a radius of approximately 20 km around the Mile High Doppler radar site.
What is a hurricane? • A large rotating storm with strong winds blowing at speeds of 74 miles per hour or more, around a relatively calm center called the eye.
Hurricane Winds Video • http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/damg/wind.rxml
It blows counterclock-wise in the Northern Hemisphere, and clockwise in the Southern Hemisphere.
The whole storm system may be 5-6 miles high, 300-600 miles wide, and move forward like as immense spinning top • Travels at speeds of about 12 mph
What causes a hurricane? • Correct amount of warmth & water vapor to supply energy • Convection activity & vertical wind motion to bring in air from sea level and move it up through the system
Must be given the right amount of spin or twist, provided by the rotating earth
What is the eye of the hurricane? • Innermost portion of the storm • Light breezes or almost windless calm • Clear skies, while winds and clouds continue raging around it
On average, eyes are 14-20 miles across • Within the eye: • Lowest pressure • Highest temperatures • Lowest relative humidity • Eye not always in the center.
Why do hurricanes form over warm oceans? • They draw their power from warm, extremely humid air found only over warm oceans. • The key to their energy source is the latent heat that is released when water vapor condenses into cloud droplets and rain.
Grow best in a deep layer of humid air that supplies plenty of moisture. • Grow where air converges and begins to push upwards. • If the air is unstable, it will continue rising after the initial shove.
When winds at all levels are blowing at the same speed in the same direction, the disturbance will grow. • Grow above high pressure areas high above the ocean, which help pump away the rising air, allowing more air to flow into the storm and rise.
What is storm surge? • Piling up of water as it is pushed along by the storm
When the storm nears land, the ocean bottom blocks the water from flowing away, and the dome of water builds up to come ashore as the storm surge • This dome of water can be as high as 18 feet deep as a storm hits land.
Storm Surge Video • http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/damg/surg.rxml
Cyclone Tracker • http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/hurr/hurtrack/index.html