|MadSci Network: Earth Sciences|
The speed of sound at 0 degrees C and standard atmospheric pressure is 1139.4 km/h (usually measured in m/s, but all the data I'm presenting is in km/h, so I've converted for comparison). Ground-level winds frequently exceed 100 km/h - southern Alberta, Canada, is a good example of a location where typical isobaric winds can reach that velocity. According to the Guinness Book of Records, the highest recorded isobaric wind speed is 333 km/h, at the USAF base at Thule, Greenland. To explore the Guinness site, go here: http://www.guinnessworldrecords.com/record_catagories/ recordhome.asp?RecordID=47490 The highest windspeeds on Earth occur in tornadoes, and the record-holder on Earth is the 1999 Oklahoma tornado, where doppler radar clocked the circular winds at 509 km/h - less than half the speed of sound. For more on the Oklahoma tornado, see: http://www.sciencenews.org/sn_arc99/5_15_99/fob1.htm It is a common misperception that the high-level jet stream is the fastest wind known. Weather services will classify an upper-air flow as a jet stream once it exceeds about 110 km/h, though jet stream speeds as high as 320 km/h have been recorded. For more on the jet stream, see: http://www.encyclopedia.com/articles/06635.html To find faster winds, we must look beyond Earth. Both Venus and Jupiter have very high winds. On Venus, top windspeeds occur in an easterly belt that flows about 370 km/h. The Galileo Probe experiment measured Jovian windspeeds from 30 km above the upper cloud deck to 80 km below. The wind speed increased from 300 km/h at the beginning of measurement to 640 km/h 45 km below the cloud tops, and remained constant for the remainder of the probe's descent. Contact was lost at the 80 km level, but it is unlikely that speeds below exceeded the maximum recorded. For more on the probe's data, see: http://www.jpl.nasa.gov/galileo/status970813.html In short, planetary wind speeds in the most extreme circumstances in our solar system do not reach more than about Mach 0.5, and current theory holds that to be the maximum obtainable speed under best (or worst, as you would have it) conditions on Earth.
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