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![Automated Surface Observing System (ASOS) - The National Weather Service (NWS), Federal Aviation Administration (FAA) and Department of Defense operate this network of 967 stations located throughout the United States [Arkansas (16), Kansas (17), Louisiana (18), Missouri (19), Oklahoma (15), Texas (60)]. The data generally available from ASOS stations includes hourly (and special) observations of air temperature, dew point, wind speed, wind direction, cloud cover, visibility, present weather, and precipitation. The hourly and special observations are included within many data archives. Additionally, data with up to one minute temporal resolution can be obtained from the ASOS stations via modem (password required for access). The most recent 12 hours of 1-minute observations are kept at the stations.](https://image.slidesharecdn.com/gatheringweatherdata-090406004112-phpapp02/75/Gathering-Weather-Data-CLASS-NOTES-12-2048.jpg)
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Gathering Weather Data CLASS NOTES
Meteorologists gather weather data from surface stations and upper-level instruments to make accurate forecasts. Surface data is collected by the Automated Surface Observing System (ASOS) using instruments like thermometers, barometers, anemometers, hygrometers, ceilometers, and rain gauges to measure temperature, air pressure, wind, humidity, cloud height, and precipitation hourly at over 967 stations across the US. Upper-level data is obtained using radiosondes, weather radars, and satellites which can detect conditions in the troposphere and provide visible and infrared images of cloud cover. This information is needed to understand changes occurring in the atmosphere.
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Gathering Weather Data CLASS NOTES
- 1. Gathering Weather Data“ Know yourself and know your enemy, and victory is guaranteed. Know the terrain and know the weather, and you will have total victory.” Chinese philosopher Sun Tzu, 4th century BC
- 2. Doctors Temperature BloodPressure Weight Height Pulse Respiration Skin/surface Meteorologists Temperature Air pressure Wind Relative humidity Clouds Rain Gathering Weather Data
- 3. Surface Data BothDoctors and Meteorologists use many different instruments to gather information Two most important factors in weather forecasting Accuracy of data Density of data (amount of data available)
- 4. Thermometers Temperature measureshow fast/slow particles are moving Fast=high temp; slow=low temp Mercury or alcohol based Liquid in bulb is heated It expands Forced up the column
- 5. Barometers Measure airpressure A rising barometer means sunny and dry conditions, while a falling barometer means stormy and wet conditions. An Italian scientist named Torricelli built the first barometer in 1643. PSI (pounds per square inch) or millibars Two types Mercury Aneroid
- 6. Mercury barometer Changesin pressure indicated by changes in height of column of mercury
- 7. Aneroid Barometer Containsvacuum in metal chamber Chamber expands or contracts with changes in pressure
- 8. Anemometer Measures windspeed Cupped arms that rotate as wind blows
- 9. Hygrometer Measures relativehumidity Wet- and dry-bulb type Sling psychrometer As water evaporates from the wet bulb, the bulb cools, creating a temperature difference between the wet bulb and the dry bulb The temperature difference is used with a relative humidity chart to determine atmospheric relative humidity p. 915
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- 11. Automated Surface ObservingSystem (ASOS) To make accurate forecasts, The different variables of Weather data must be gathered at the same moment, several times a day, at many different locations The National Weather Service (NWS) has a network of approx. 1700 official weather observing sites to measure and record data at least every hour The ASOS collects all this information using the instruments we talked about in addition to rain gauges and ceilometers
- 12. Automated Surface ObservingSystem (ASOS) - The National Weather Service (NWS), Federal Aviation Administration (FAA) and Department of Defense operate this network of 967 stations located throughout the United States [Arkansas (16), Kansas (17), Louisiana (18), Missouri (19), Oklahoma (15), Texas (60)]. The data generally available from ASOS stations includes hourly (and special) observations of air temperature, dew point, wind speed, wind direction, cloud cover, visibility, present weather, and precipitation. The hourly and special observations are included within many data archives. Additionally, data with up to one minute temporal resolution can be obtained from the ASOS stations via modem (password required for access). The most recent 12 hours of 1-minute observations are kept at the stations.
- 13. Ceilometers Measure cloudheight and cloud cover Uses laser pulses
- 14. Ground-Based Description ofSky Conditions Cloud Observations - Ground-based Description ASOS (NWS) Human Meaning Clear (CLR or SKC) 0to 5% 0 No Clouds Few >5 to <25% 0 to 2/8 Few clouds visible Scattered (SCT) > 25 to <50% 3/8 to 4/8 Partly cloudy Broken (BKN) > 50 to <87% 5/8 to 7/8 Mostly cloudy Overcast (OVC) > 87 to 100% 8/8 Sky is covered by clouds Sky obscured NA NA Sky is hidden by surface-based phenomena, such as fog, blowing snow, smoke and so forth, rather than by cloud cover
- 15. Rain gauge Measuresamount of precipitation
- 16. Upper Level DataMore complex technology is needed to collect data from the upper troposphere Remember: changes in the upper atmosphere changes weather at Earth’s surface
- 17. Radiosonde Balloon-borne instrumentContains sensors to collect upper level variables such as relative humidity, temperature, wind speed and direction, and air pressure Radio signal transmits info to ground station
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- 19. Weather radar Usedto predict areas of precipitation Transmitter emits electromagnetic waves thru antennae When waves hit water droplets, they are reflected, making an echo picked up by receiving antennae Elapsed time between transmission and echo reception is used to determine where rain is falling Radar systems have range 400 km in diameter
- 20. Doppler Radar Similarto radar systems but with added advantage: measure wind speeds associated with storms Based on Doppler effect Change in wave frequency that occurs as source of waves moves towards or away from the observer Ex. Ambulance siren High pitched as it approaches and low pitch as it leaves By plotting echos of radar signals, meteorologists can determine speed at which rain drops are moving towards or away from the receiving antennae
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- 24. Weather Satellites Orbithigh enough above the surface and transmit images to Earth’s weather stations Visible Picture of clouds Infrared Does not need light…uses infrared radiation istead of visible light to make image tells you the temperature of what the satellite is sensing, whether its the ground or the tops of clouds very useful for determining the height of the cloud (low, middle, high) Low clouds=warm High clouds=cold Good for detecting thunderstorms high up in atmosphere
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