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Ancient Wind Measurement

Ancient Wind Measurement. Wind vanes were perhaps the most ancient meteorological instruments. Mesopotamian and Sumerian documents, dating back nearly 4,000 years, describe primitive wind vanes, and streamers were used for wind direction measurement in China during the second century B.C.E.

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Ancient Wind Measurement

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  1. Ancient Wind Measurement • Wind vanes were perhaps the most ancient meteorological instruments. • Mesopotamian and Sumerian documents, dating back nearly 4,000 years, describe primitive wind vanes, and streamers were used for wind direction measurement in China during the second century B.C.E.

  2. Wind Measurement • The famous Tower of the Winds in Athens, dating back at least to 50 B.C.E., was topped by a wind vane in the form of a Triton • Wind vanes and wind banners were common during the Middle Ages, and were found on many churches, ships, and towers.

  3. Wind Vane

  4. Development of anemometers

  5. Modern Three-Cup Anemometer

  6. Combo

  7. Sometimes anemometers and wind vanes have had icing issues.

  8. NewSonic Anemometer Old The solution….

  9. Sonic Anemometer

  10. Proper Exposure of Wind Instruments • Open area • Sensors at 10 m (roughly 30 ft) above the ground • Not right above pitched roof.

  11. Sustained Winds and Wind Gusts • Sustained: usually average of 1-2 minutes • Gusts: typically strongest 3-5 second average wind reported. • Typically about a 1.3-1.4 ratio for (gust/sustained), but can be much more in some occasions.

  12. You Can Often See Gusts Over Water—called “cat’s paws”

  13. Why Gusts?

  14. Winds are often far stronger over water than land • Water is much smoother aerodynamically than land • Trees, building, hills, etc. all slow down winds near the surface. • Wind over water can be 50-100% stronger (or more) than over land.

  15. Estimating Wind Subjectively • Wind direction: flags, low clouds, trees and branches, throw grass in air • Wind speed: Beaufort Scale

  16. Sir Francis Beaufort, 1805

  17. Wind Terminology • Gale: 34-47 knots • Storm: 48-64 knots • Hurricane: 65+ knots

  18. Strongest Near Surface Winds • Anemometer: 231 mph, Mt. Washington, NH 1934 • Radar: 318 mph, OK City Tornado, 3 May 1999

  19. Columbus Day 1962: At Cape Blanco there were 150 mph with gusts to 179! Strongest winds on bluffs and windward slopes of coastal orography

  20. Why Wind? • Created by differences in pressure. • Air accelerates from high to low pressure

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