Ten o’clock is solar tide time

March 9th, 2009  |  by  |  Published in Research News

Hamilton, right, and co-author Ryan with pressure sensor

Hamilton, right, and co-author Ryan with pressure sensor

Observing that atmospheric pressure in the tropics peaks at 10 a.m. and 10 p.m. nearly every day, meteorologists theorized that the cause was “solar tides” generated when the sun heats the upper atmosphere.

A new study by the International Pacific Research Center provides convincing evidence for the 40-year-old theory.

University of Hawaiʻi at Mānoa Professor Kevin Hamilton predicted that shadow regions for these waves would be created to the west of steep mountain peaks.

Working with Wataru Ohfuchi of Japan’s Earth Simulator Center, Hamilton applied sophisticated computer models. Working with Steve Ryan of NOAA’s Mauna Loa Observatory, he analyzed real observations from a network of pressure sensors on the mountain. Both demonstrated weaker pressure variations in the predicted shadow regions.

The findings appear in the Sept. 6, 2008 issue of Journal of Geophysical Research–Atmospheres, whose editors awarded the paper the rare distinction of research highlight.

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