MountainsMountains

SPI 0507.8.2 SPI 0507.8.2 Explain how Explain how mountains affect weather and mountains affect weather and climate. climate.

Three WaysThree Ways

In this PowerPoint you are going to study three ways mountains affect climate.– Elevation– Rain Shadows– Mountain and Valley Breezes

How Mountains Affect Weather & Climate

Number 1 - Elevation

Have you ever noticed as you are driving into Mountain City from Bristol or Johnson City that the temperatures get cooler?

Johnson CountyJohnson County

How many times have you seen snow on the top of Snake Mountain when there was none in Mountain City?

The reason for this is the elevation.

Mountain City has the highest elevation of any city in Tennessee at 2350 feet above sea level. The highest point in Johnson County is Snake Mountain at an elevation of 5574 feet above sea level.

ElevationElevation

• The higher the elevation, the lower the temperature becomes.

• The rate at which the temperature drops is known as the lapse rate. On average, the lapse rate is 3.6 degrees per 1,000 feet.

Elevation DifferencesElevation Differences

• With Snake Mountain over 2000 feet higher in elevation than Mountain City, the temperature on top of Snake Mountain could easily be 7 degrees cooler.

How Mountains Affect Weather & Climate

Number 2 - Rain Shadows

Rain ShadowsRain Shadows

Mountains greatly affect the climate. They act as barriers blocking rain and wind.

One side of the mountain may have a very different climate from the other side. In some cases mountains create a shadow. This is where rain does not fall. Deserts can form in the rain shadow regions.

AnimationsAnimations

• http://www.mhhe.com/biosci/genbio/tlw3/eBridge/Chp29/animations/ch29/rain_shadow_formation.swf

• http://bio1100b.nicerweb.com/med/Vid/Discover2e/ch39a04_RainShadow.swf

• http://www.uky.edu/AS/Geology/howell/goodies/elearning/module07swf.swf

• http://www.mrphome.net/mrp/rainshadow.swf

Example – Rain ShadowExample – Rain ShadowDeath Valley in the United States is behind

the Pacific Coast Ranges of California and the Sierra Nevada range.

BrainPopBrainPop

• http://www.brainpop.com/science/earthsystem/mountains/

How Mountains Affect Weather & Climate

Number 3 –

Mountain Breezes and Valley Breezes

Mountain Breeze –Valley BreezeMountain Breeze –Valley Breeze

Mountain and valley breezes are very similar to land and sea breezes.

Remember – Air pressures try to equalize themselves through wind. High pressures move toward low pressures.

During the day the surface of the mountain heats the air high up in the atmosphere quicker than the valley floor can. This creates a low pressure area near the top of the mountain. Wind moves from the valley where the air pressure is high to equalize this pressure.

Day – Valley BreezeDay – Valley Breeze

When the wind moves from the valley to the top of the mountain, this is called a valley breeze.

During the night the mountain tops cool more quickly than the air in the valleys. This creates a high pressure area at the mountain top where the air becomes more densely packed.

The wind changes direction and moves from the mountain top to the valley floor to equalize this high pressure.

Mountain Breeze –Valley BreezeMountain Breeze –Valley Breeze

Most of the time we see valley breezes during the day, as winds blow from the valley up towards the mountains. During the night we see mountain breezes, as winds travel from the mountains, down towards the valleys.

Animation Animation

• http://www.bborucki.com/wind.swf