Ancient Wind Measurement Wind vanes were perhaps the

  • Slides: 37
Download presentation
Ancient Wind Measurement • Wind vanes were perhaps the most ancient meteorological instruments. •

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.

101 Wind

101 Wind

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

Why Wind? • Created by differences in pressure. • Air accelerates from high to low pressure • Wind is simply the movement of air

Ancients had other ideas…

Ancients had other ideas…

Wind Measurement • The famous Tower of the Winds in Athens, dating back at

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.

Wind direction can be measured with wind vanes

Wind direction can be measured with wind vanes

More modern version

More modern version

Wind speed is measured using anemometers

Wind speed is measured using anemometers

Development of anemometers

Development of anemometers

Modern Three-Cup Anemometer

Modern Three-Cup Anemometer

Combo

Combo

Sometimes anemometers and wind vanes have had icing issues.

Sometimes anemometers and wind vanes have had icing issues.

New Sonic Anemometer Old The solution….

New Sonic Anemometer Old The solution….

Sonic Anemometer

Sonic Anemometer

Wind Terminology • Wind direction is the direction from which the wind is coming

Wind Terminology • Wind direction is the direction from which the wind is coming – Easterly wind from the east – Westerly wind from the west • Given in cardinal directions. . or. .

Wind Direction (degrees) Professionally—generally degrees used

Wind Direction (degrees) Professionally—generally degrees used

Speed • Generally given in knots – 1 knot = 1 nautical mile per

Speed • Generally given in knots – 1 knot = 1 nautical mile per hour= 1. 15 mph – 1 knot is ~. 5 meter per second

Proper Exposure of Wind Instruments • Open area • Sensors at 10 m (roughly

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

Sustained Winds and Wind Gusts • Sustained: usually average of 1 -2 minutes •

Sustained Winds and Wind Gusts • Sustained: usually average of 1 -2 minutes • Gusts: typically strongest 3 -5 second average wind reported during a period. • Typically about a 1. 3 -1. 4 ratio for (gust/sustained), but can be much more in some occasions.

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

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

Why Gusts?

Why Gusts?

Winds are often far stronger over water than land • Water is much smoother

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.

Estimating Wind Subjectively • Wind direction: flags, low clouds, trees and branches, throw grass

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

Sir Francis Beaufort, 1805

Sir Francis Beaufort, 1805

Wind Terminology • Gale: 34 -47 knots • Storm: 48 -64 knots • Hurricane:

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

Strongest Near Surface Winds • Anemometer: 231 mph, Mt. Washington, NH 1934 • Radar:

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

The NW Wind Record

The NW Wind Record

Columbus Day 1962: At Cape Blanco there were 150 mph with gusts to 179!

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