Weather

Using Köeppen’s classification system, Yellowstone National Park is classified as BSK.  This means it is a dry, steppe dessert area.  Although it has a definite classification, the park’s website describes its weather as unpredictable.  Weather and climate are erroneously used interchangeably.  Weather is the atmosphere’s condition at any given moment while climate refers to the atmosphere’s average condition over long periods of time.

Courtesy of Google Images

This unpredictable weather is extremely important to the many hikers that visit the park yearly.  Yellowstone’s weather and climate are a product of its location.  First, the Rocky Mountains cut across the park and have an orographic effect on precipitation, winds and temperature.  This occurs when warm moist air collides with the Rockies and is forced up the windward side of the mountains.  When it hits the lifting condensation level clouds and water droplets are formed.  At this point the temperature will begin dropping 3°F for every 1,000 feet of gained elevation.  As it goes over the mountain and descends on the leeward side it becomes a dry, warm down slope surge known as the Chinook winds.  The descending altitude will have a warmer temperature of 5.5 ° F for every 1,000 feet of descent.

Courtesy of Google Images

Second, the altitude of the park has a lot to do with the temperature as well.  The average elevation is 8,000 feet ranging from 5,282 to 11,358 feet.  Atomospheric pressure decreases with altitude.  With the decreased pressure, the air expands as it rises.  As it expands the molecules move slower and the air becomes cooler than at sea level.  This fact lead to the Environmental Lapse Rate (ELR) which states that temperature will drop an average of 3° F for every 1,000 feet above sea level.  This means that on average, temperatures will be 24° F colder than sea level.

Courtesy of Google Images

Courtesy of Google Images

References:

http://www.yellowstone-natl-park.com/weather.htm

http://www.nps.gov/yell/planyourvisit/weather.htm

http://www.yellowstonenationalpark.com/geology.htm

http://clasfaculty.ucdenver.edu/callen/1202/Climate/Weather/LCL.gif

http://clasfaculty.ucdenver.edu/callen/1202/Climate/Weather/ELR.gif

http://education.sdsc.edu/teachertech/downloads/climate_answ.pdf

http://www.google.com/search

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