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EESA09 - Wind Lecture #8 - Measuring Winds fully solved
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EESA09 - Wind Lecture #8 - Measuring Winds fully solved
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EESA09 - Wind Lecture #8 - MeasuringWinds fully solved
How do you measure Wind direction? - correct answer ✔✔wind vane/weather vane
How to measure Wind Speed? - correct answer ✔✔Anemometer
Types of Anemometers; DEFLECTION ANEMOMETER - correct answer ✔✔- 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 ✔✔- 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 ✔✔- 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 ✔✔- uses propeller to measure
wind speed
- aerovane used to ensure anemometer is pointing into the wind
, Types of Anemometers; THERMOELECTRIC ANEMOMETER - correct answer ✔✔- 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 ✔✔- 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 ✔✔- 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 ✔✔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 ✔✔- 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
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