CLIMATECLIMATE

Weather vs Climate• Weather: what is happening in the

atmosphere at a particular place and time– Ex: Daily weather forecast for Minneapolis 24ºF, couple of flurries, clearing of

clouds, cool

• Climate: average weather in an area, over a long period of time– Temperature, Humidity, Wind and

Precipitation– Ex: warm summers, cold winters

What determines climate?

1. Latitude- amount of solar energy received

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Equator: vertical raysPoles: oblique rays

2. Atmospheric Circulation Pattern- Cold air sinks and warms as it sinks

- Warm air rises and cools as it rises

- Warm air can hold more water vapor than cold air

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Moisture is sucked from the surface at 30 degrees north and 30 degrees south because the air masses areincreasing in temperature and are able to hold more water

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3. Ocean Circulation Patterns

Water holds a lot of heat “Conveyor belt”

• 4. Local geography

–Mountains and mountain ranges

El Niño• Named for “The Christ Child” because it comes

around x-mas• Disruption of the ocean-atmosphere system in the

Tropical Pacific• Abnormal warming of the surface waters

– Consequence: global weather and climate change

Strongest year: 1997-1998

From NOAA-November 5, 2009

• El Nino is expected to continue strengthening and last through at least the Northern Hemisphere winter 2009-2010.

• Expected El Nino impacts during November 2009-January 2010 include enhanced precipitation over the central tropical Pacific Ocean and a continuation of drier-than-average conditions over Indonesia. For the contiguous United States, potential impacts include above-average precipitation for Florida, central and eastern Texas, and California, with below-average precipitation for parts of the Pacific Northwest. Above-average temperatures and below-average snowfall is most likely for the Northern Rockies, Northern Plains, and Upper Midwest, while below-average temperatures are expected for the

southeastern states.

An El Niño condition results when the trade winds pushing the water around get weaker.

• As a result, some of the warm water piled up in the west slumps back down to the east, and not as much cold water gets pulled up from below.

• Both these tend to make the water in the eastern Pacific warmer, which is one of the hallmarks of an El Niño.

• But it doesn't stop there. • The warmer ocean then affects the winds--it

makes the winds weaker! • So if the winds get weaker, then the ocean

gets warmer, which makes the winds get weaker, which makes the ocean get warmer ... this is called a positive feedback, and is what makes an El Niño grow.

La Niña

• Cold sea-surface temperatures in the eastern Pacific

• Conditions recur every few years and could persist for as long as two years

• Effects opposite of el Niño in most locations

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Hurricanes

• Forms over really warm water (80° F +)• Atmosphere cools off very quickly the higher

you go• Winds must be blowing in the same direction

and at the same speed to force air up

• Typically form between 5 to 15 degrees latitude north and south of equator

Places on Earth where conditions are met for hurricane formation

http://www.comet.ucar.edu/nsflab/web/hurricane/324.htm

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2008/es2008page01.cfm?chapter_no=visualization

Animation of hurricanehttp://news.bbc.co.uk/1/hi/sci/tech/4588149.stm