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6 Pages

Environmental Science
Course Code
Tanzina Mohsin

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MEASURING WIND - wind direction wind vane or weather vane - wind speed anemometer what type of device is used to measure higher level winds? These winds are measured using radiosonde (weather balloons) or deduced using pressure distribution - radiosonde is used to deduce pressure measurements. - Upper level winds are geostrophic , so the knowledge of pressure gradient enables us to calculate… WIND SPEED AND DIRECTION PEOPLE TO REMEMBER - Leon Batista Deflection anemometer - James Lind pressure anemometer - Thomas. R. Robinson four cup anemometer - John Patterson three cup anemometer - Dr. Andreas Pflitschsonic anemometer - FITROY thermometer - TORICELLIbarometer DEFLECTION ANEMOMETER - Was the first anemometer - The first anemometer (deflection) was invented by ? Leon Batista Alberti in Italy in 1450 - How does a deflection anemometer work? He linked wind speed to the deflection of a horizontal plate. - Wind pushed horizontal platethe plate is connected to a springcompression of the spring is proportional to WIND SPEED - Leonardo Da Vinci created a similar anemometer a few decades later - A century later Robert HOOKE of England created a Hooke anemometer Pressure Anemometers - James Lind in 1774 developed a tube anemometer - U tube – wind blows into tube and pushes liquid in the tube - How does a tube anemometer work? Wind blows into the tube, and causes liquid to move up and down the tube. The anemometer measures the force of the wind, relative to the force the gravity. - WHAT DOES THE PRESSURE ANEMOMETER MEASURE?force of wind, relative to force of gravity - Higher wind speed- greater the amount of displaced liquid - Dines anemometer - 1892 Cup anemometer - The cup anemometer was invented in 1846 by Thomas R. Robinson of England. - How many cups did the anemometer have? It had four cups that were 90 degrees apart. - What is the relationship between cup speed and wind speed? The relationship is that, cup speed is nearly 1/3 of wind speed. - What is an advantage of the cup anemometer ? An advantage of the cup anemometer is that it doesn’t need to be reoriented as the wind direction changes. It changes direction on its own - Who created the three cup anemometer? The three cup anemometer was created in 1926 by Canadian John Patterson. It proved to be more accurate, usually within 3% up to 100 km/h. Windmill Anemometer - Similar to a cup anemometer but, it uses a propeller rather than a cup to gauge the wind - speed. - What is used to ensure that the anemometer is pointing into the direction of the wind? Aerovane. Thermoelectric Anemometerwind cooling effects - Thermoelectric anemometers involve the use of? A wire - How is this wire used as a part of the device ? In a thermoelectric anemometer a wire is heated to above the ambient temperature. - How does the device work? The rate of cooling of the wire is PROPORTIONAL TO THE WIND SPEED. - How can u distinguish the different types of winds ? Higher speed winds cool objects more quickly. - What is an advantage of the device? The instrument has the advantage of no moving parts. Laser Radar Anemometer - What principle does the Laser Radar Anemometer follow? It follows the Doppler principle , to measure wind speed. - What is the Doppler principle? Explains how sound waves from objects moving towards us have a higher pitch (frequency) , than sound waves moving away from us (lower frequency) - So , objects close to us have a HIGHER FREQUENCY , and objects away from us have a LOWER FREQUENCY - This explains the apparent change in pitch of train whistles and emergency vehicle sirens as the vehicles travel past. - How does the anemometer work ? uses a LASER BEAM, A fraction of the laser light reflects off of nearby air molecules; some of this is returned to the anemometer (backscatter). - Operates off of backscattered light - What is backscattered light? The laser light reflects off of NEARBY AIR MOLECULES, and some of this light returns to the anemometer. - How is this anemometer used? The frequency of the backscattered light indicates the speed of the air molecules (and wind) Sonic Anemometer - Dr. Andreas Pflitsch - Measures how sound waves are modified by wind. (CHANGE IN THE SPEED OF SOUND) Anemometers 1. Pressure- based on  hydrostatic balance created by James Lind 2. Deflection wind pressure displacement created by Leon Batista 3. Cup mechanical movement created by Thomas R. Robinson (four cup) , John Patterson (three cup) 4. Windmill mechanical movement 5. Thermoelectric based on wind cooling effects 6. Sonic based on the change in speed of sound created by Andreas Pflitsch 7. Lasar radar based on dopplar radar Measuring upper level winds - Upper level winds can be deduced from what? - Radiosonde drift (weather balloon) - Aircraft - Deduced from pressure structure o Geostrophic winds 1.1.2 Measuring Upper Level winds what type of device is used to measure higher level winds? These winds are measured using radiosonde (weather balloons) or deduced using pressure distribution - radiosonde is used to deduce pressure measurements. - Upper level winds are geostrophic , so the knowledge of pressure gradient enables us to calculate… WIND SPEED AND DIRECTION RADIOSONDES - How do you measure upper level winds? Upper level winds are determined from … measurements of RADIOSONDES , Radiosondes , are WEATHER BALLOONS - When are radiosondes launched? Radiosondes are launched form meteorological stations around the world twice a day , 0:00 and 12:00 UTC *universally coordinated time* Upper level winds are determined through measurements from radiosondes - This provides meteorologists with a synoptic observation of the atmosphere (simultaneous) - What does a radiosonde measure? Temperature, pressure, humidity, wind speed - Where do the radiosondes POP? Radiosondes travel through the TROPOSPHERE and much of the stratosphere and tend to “pop” at about 30 KM in altitude. - What is It used for ? it can measure the wind speed directly , but its mostly used to record changes in pressure at specific altitudes. - What can meteorologists do with horizontal pressure gradients? W
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