Atmospheric Pressure Variation StudyManoa’s Kevin Hamilton explores the sun’s effect on the upper atmosphere. Read more
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Steve Ryan, left, and Kevin Hamilton
Atmospheric Pressure Variation Study
Manoa Professor Kevin Hamilton led a team of researchers in a study on daily variation in atmospheric pressure. The study results support the theory that pressure variations result from waves that are generated by the sun's heating of the upper atmosphere. The waves, called solar tides, propagate to the ground as they travel around the globe. The findings were published in the Journal of Geophysical Research.
Hamilton reasoned that if the proposed explanation was correct, then the pressure variations should be affected systematically by topography. Since mountains cast a kind of shadow for the atmospheric wave as it propagates westward (following the sun) and downward, he predicted that the pressure variations should be weaker on the west than the east side of steep mountains.
Working with Wataru Ohfuchi of the Japanese Earth Simulator Center in Yokohama, Hamilton was able to show that this topographic effect is seen in very sophisticated computer model simulations of the global atmosphere.
One of the most dramatic examples of the shadow effect in the computer model results occurs with the tall mountains of the Big Island. Working with Mauna Loa Observatory’s Steve Ryan, Hamilton was able use the network of pressure sensors to show that the shadow effect is seen in these real pressure observations as well. The Hawai’i results shed light on an important feature of the global atmosphere.