ATMOSPHERIC PRESSURE, WIND & CLOUDS Mt. Washington Observatory
ATMOSPHERIC PRESSURE Weight of the air above a given area p = F/A Measured in mb (millibars) Average Atmospheric Pressure at 0m (Sea Level) is 1013mb Your book
PRESSURE 50 miles (Barometer measures 1013mb)
PRESSURE 500mb pressure 1013mb pressure As you go up in altitude, there’s less weight (less molecules) above you… …as a result, pressure decreases with height!
ATMOSPHERIC PRESSURE Your book
ATMOSPHERIC PRESSUREPRESSURE VARIATIONS Barometers OVER PVD Buybarometers.com
CAUSES OF PRESSURE VARIATIONS Universal Gas Law PV = nRT Pressure depends on: Number of Moles, Volume, Density, and Temperature of all the air above PVD
SEA LEVEL PRESSURE VARIATIONS - RECORDS Lowest pressure ever recorded in the Atlantic Basin: 882 mb Hurricane Wilma, October 2005 Highest pressure ever recorded in the world: 1086 mb Mongolia, December 2001
Pressure Differences cause Air to move
PRESSURE GRADIENT FORCE
EARTH’S ROTATION
ROTATION OF THE EARTH
ROTATION OF THE EARTH
ROTATION OF THE EARTH
ROTATION OF THE EARTH
ROTATION OF THE EARTH
CORIOLIS EFFECT
CORIOLIS EFFECT
WIND
WIND
HOW IS THIS APPLIED? NORTH WINDS COLD MODERATE SOUTH WINDS WARM http://ww2010.atmos.uiuc.edu/(Gh)/wx/surface.rxml
VALIDATION Coolwx.com
VALIDATION H L Coolwx.com
VALIDATION H L NCAR UCAR RAP Realtime weather (http://www.rap.ucar.edu/weather/satellite/)
SUMMARY UP TO THIS POINT 1) Differences in atmospheric pressure across the globe lead to winds across the surface of the planet 2) The PRESSURE GRADIENT FORCE pushes air from high to low pressure (WIND) 3) The BIGGER the difference between high and low pressure the STRONGER the wind 3) As air moves away from high pressure and towards low pressure, the CORIOLIS EFFECT deflects it to its right (NH) 4) The above leads to air circulating COUNTER-CLOCKWISE around LOW PRESSURE and CLOCKWISE around HIGH PRESSURE (NH) 5) South or North winds will result in higher or lower temps
WHAT ABOUT THE CLOUDS? Remember that air converges towards low pressure and air diverges away from high pressure and FRICTION due to the surface of Earth “enhances” this
WHAT ABOUT THE CLOUDS? So, as the air moves towards the low pressure it has nowhere to go but UPWARDS
WHAT ABOUT THE CLOUDS? So, as the air moves away from high pressure it must be replaced by air from above that is moving DOWNWARDS
TEST A World of Weather (Lee Grenci PSU)
INTERESTING NOTE!
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