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Measuring Winds: Techniques and Principles, Exams of Nursing

Abilene Christian University (ACU)Nursing

A comprehensive overview of the various methods and instruments used to measure wind direction and speed. It covers the history, working principles, and applications of different types of anemometers, including deflection, pressure, cup, windmill, thermoelectric, laser radar, and sonic anemometers. The document also discusses the measurement of upper-level winds using radiosondes and dropsondes, as well as the concepts of geostrophic winds, wind chill, and the beaufort scale. Additionally, it explores the relationship between sound and wind, including the speed of sound in the atmosphere, the phenomenon of thunder and lightning, and the mach scale. This detailed and informative document would be valuable for students and researchers interested in meteorology, atmospheric science, or wind energy applications.

Typology: Exams

2023/2024

Available from 10/25/2024

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EESA09 - Wind Lecture #8 - Measuring
Winds fully solved
How do you measure Wind direction? - correct answer โœ”โœ”wind vane/weather vane
How to measure Wind Speed? - correct answer โœ”โœ”Anemometer
Types of Anemometers; DEFLECTION ANEMOMETER - correct answer โœ”โœ”- 1st one
- 1450 Leon Battista in Italy
- Horizontal plate pushed by wind and connected to a spring
- compression of the spring proportional to wind speed
** Not good for light winds
Types of Anemometers; PRESSURE ANEMOMETER - correct answer โœ”โœ”- James lind 1774
- tube anemometer
- U tube - wind blows into a tube & pushes liquid in the tube
- (Dines anemometer 1892)
Types of Anemometers; CUP ANEMOMETER - correct answer โœ”โœ”- Thomas R. Robinson 1846
- 4 cups
- cup speed is 1/3 of the wind speed
- 3 Cup Anemometer - Canadian John Patterson
- more consistent behavior <3% error up to 100 km/h
Types of Anemometers; WINDMILL ANEMOMETER - correct answer โœ”โœ”- uses propeller to measure
wind speed
- aerovane used to ensure anemometer is pointing into the wind
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EESA09 - Wind Lecture #8 - Measuring

Winds fully solved

How do you measure Wind direction? - correct answer โœ”โœ”wind vane/weather vane How to measure Wind Speed? - correct answer โœ”โœ”Anemometer Types of Anemometers; DEFLECTION ANEMOMETER - correct answer โœ”โœ”- 1st one

  • 1450 Leon Battista in Italy
  • Horizontal plate pushed by wind and connected to a spring
  • compression of the spring proportional to wind speed ** Not good for light winds Types of Anemometers; PRESSURE ANEMOMETER - correct answer โœ”โœ”- James lind 1774
  • tube anemometer
  • U tube - wind blows into a tube & pushes liquid in the tube
  • (Dines anemometer 1892) Types of Anemometers; CUP ANEMOMETER - correct answer โœ”โœ”- Thomas R. Robinson 1846
  • 4 cups
  • cup speed is 1/3 of the wind speed
  • 3 Cup Anemometer - Canadian John Patterson
  • more consistent behavior <3% error up to 100 km/h Types of Anemometers; WINDMILL ANEMOMETER - correct answer โœ”โœ”- uses propeller to measure wind speed
  • aerovane used to ensure anemometer is pointing into the wind

Types of Anemometers; THERMOELECTRIC ANEMOMETER - correct answer โœ”โœ”- heated wire to above the ambient temp

  • rate of cooling of wire is proportional to wind speed
  • in ancient times hair was used Types of Anemometers; LASER RADAR ANEMOMETER - correct answer โœ”โœ”- same principle as Doppler Radar (Shift in frequency i.e. train whistle at railway crossings, sirens on emergency vehicles)
  • laser beams are back-scattered by moving air molecules
  • Doppler shifted frequency of the back-scatter indicates wind speed Types of Anemometers; SONIC ANEMOMETER - correct answer โœ”โœ”- Dr. Andreas Pflitsch 1994 (geologist)
  • Measures how sound waves are modified by the wind
  • deduces wind speed Upper Level Winds: Radiosonde Drift (Weather Balloon) - correct answer โœ”โœ”Radiosonde: an instrument carried by balloon or other means to various levels of the atmosphere and transmitting measurements by radio.
  • measures temp, pressure, humidity, wind
  • usually pop around 30 km (halfway through Stratosphere)
  • 34 in Canada, 1500 world wide Dropsonde: Instruments dropped from Airplane
  • designed to be dropped from an aircraft at altitude to more accurately measure (and therefore track) tropical storm conditions as the device falls to the surface Upper Wing Calculations - Geostrophic Winds - correct answer โœ”โœ”- Balance between PGF and Coriolis:
  • Geostrophic winds are when pressure gradient force pulls from high pressure to low pressure
  • coriolis force pulls moving objects to the right in NH and left in SH
  • strength of Coriolis force is proportional to the speed of the object
  • friction is negligible in upper level winds
  • Typically hourly data is used for a 30 year period
  • a diagram showing the relative frequency of wind directions at a place. Local Winds - correct answer โœ”โœ”- Sound in the Atmosphere - correct answer โœ”โœ”- sound is transmitted by air molecules pushing against each other
  • speed of sound in the atmosphere: 344 m/s at 21 deg C at sea level
  • speed in inversely proportional to density Increases with increasing temperature Increases with increasing humidity Decreases with increasing altitude (temperature decreases with altitude) Thunder & Lightning - correct answer โœ”โœ”- scary sound effect
  • Thunder/lightning are produced by same phenomenon
  • lightning produces a localized region of >28,000 Deg C- thermal expansion produces a shock wave, heard as thunder
  • lightning travels at the speed of light in air (300,000 km/s)
  • thunder travels at the speed of sound in air (344 m/s)
  • light is little less than 1 M times faster
  • delay of three seconds betwen lightning/thunder indicates that the lightning strike was 1 KM away Beaufort Scale - correct answer โœ”โœ”- Sir Francis Beaufort (1774-1857) (Admiral)
  • 1788 - First voyage (shipwrecked)
  • joined royal navy in 1790
  • scale devised from ocean observation from 1805 to 1810
  • 12 point qualitative scale

Subsequently adapted to specific winds speeds

  • 1 knot = 1.8 km/ Tornadoes - correct answer โœ”โœ”- Strongest winds on the planet
  • strongest hurricane would fall in F3 Tornado Range Saffir-Simpson Scale - correct answer โœ”โœ”- developed for hurricane damage estimation in the Atlantic Basin by the Head of NHC (US) Mach Scale - correct answer โœ”โœ” Mach Number - correct answer โœ”โœ”- the ratio of the speed of an object to the speed of sound M = v/vs If M > 1 then the object is exceeding the speed of sound At 15oC at sea level, speed of sound is 330 m/s (1190km/h), at 21oC at sea level it is 344 m/s (Speed of sound does vary with temperature Sonic Boom - correct answer โœ”โœ”- Prandt-Glauret Singularity
  • Cone shaped cloud that forms at transonic speeds
  • Sonic compression wave is formed
  • intense pressure is followed by a region of much lower pressure
  • lower pressure causes steep drop in temp below dew point
  • this leads to condensation and the visible cone
  • ie. thunder is a sonic boom resulting from lightning strike
  • bullwhip - snapping sound occurs when lower end of whip exceeds speed of sound
  • Aircraft - supersonic jets, concorde