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www.westcoastweathervanes.com Observations and Station Models AOS 101 Discussion Sections 302 and 303 Observations What do we mean by observations? Importance of observations Collecting data through various instruments Assess current state of atmosphere Also aid in predicting future weather Can be taken by people or automated sensors Examples Buoys Ships Commercial aircraft (ACARS) Satellites www3.sympatico.ca noaanews.noaa.gov Types of Observations farm4.static.flickr.com Air temperature Dew point temperature Air pressure Humidity Wind speed and direction Cloud cover Ocean salinity Etc… Air Temperature Air temperature is measured by a thermometer www.freefoto.com www.weatherconnect.com www.faqs.org Dew Point Temperature Dew point temperature www.earlywomenmasters.net www.edupic.net The temperature at which water precipitates out of the air Can be measured by a hygrometer Can be calculated by using observations from a wet bulb thermometer or psychrometer Wet Bulb Temperature Measured with a thermometer that has a moist cloth over the glass bulb A simpler way to think of it The wet-bulb temperature is reached when the air temperature is high enough to evaporate the water from the cloth The temperature you feel when your arm is exposed to moving air Can also be measured by a psychrometer www.labsafety.com Pressure Units Hectopascals (hPa) Millibars (mb) Inches of mercury (inHg) Why is pressure important? Low pressure systems indicate cooler or stormy weather High pressure systems indicate warmer or drier weather Measured by a barometer www.navyleagueshipsstore.com Wind Speed and Direction Wind speed is measured by an anemometer www.bom.gov.au Weather vanes and wind socks tells us wind direction www.greensvanes.co.uk www.sportys.com Air Pollution The concentration of pollutants can be measured by an aerosol monitor blog.lib.umn.edu www.industrysearch.com.au windows2universe.org Heat Index The “apparent temperature” How hot it really feels when relative humidity is taken into account with air temperature Wind Chill A description of “coldness” The discomfort or danger resulting from wind and air temperature Values found by calculation Radiosonde A balloon-borne instrument platform that transmitts its observations via radio What does it measure? Radio – radio transmitter Sonde – messenger in Old English Air Temperature Pressure Humidity Wind Speed (indirectly) It reaches a height of ~30km and at that height the balloon swells to a 30 foot diameter! www.ucar.edu Radiosonde Instrumentation Thermistor (Temperature) Hygristor (Humidity) Aneroid Barometer (Pressure) www.plymouth.edu Can be used to detect different atmospheric layers Radio Transmitter & GPS Balloon & Parachute artemis.rsmas.miami.edu Can be used to find dew point Radiosondes cost approximately $300 and most of the time the instruments are never found Sounding Diagram rap.ucar.edu Main Cloud Name Elements Alto Cirrus Fluffy Nimbus Thin and wispy Cumulus High Raincloud Stratus Layer or spreadout Low-Level Clouds (~5,000 ft) Stratus Form in low horizontal layers having a frayed or uniform base Stratocumulus Puffy clouds that form following a cold front Can produce light rain www.colby.edu upload.wikimedia.org Stratus Stratocumulus Low-Level to Mid-Level Clouds Cumulus Fair weather clouds, fluffy From below ~6,500 ft to ~10,000 ft Nimbostratus Constant precipitation and low visibility Above ~6,500 ft upload.wikimedia.org Cumulus www.maltaweather.info Nimbostratus Mid-Level Clouds (~15,000 ft) Altostratus Occurs when a when an air mass is lifted to the point where it condenses Usually produces rain or snow Altocumulus Formed by mid-level convective instability www.victoriaweather.ca Altostratus upload.wikimedia.org Altocumulus High-Level Clouds Cirrostratus Occurs when moist air cools to saturation at a high altitude Made of ice crystals Cirrocumulus Cirrostratus mw2.google.com Same as cirrostratus, but has convective instability Cirrus Cirrocumulus Happens at the highest part of the tropopause Usually means a storm is approaching upload.wikimedia.org upload.wikimedia.org Cirrus Vertically Developed Clouds Cumulonimbus Develop from cumulus when the air mass is highly unstable Usually forms thunderstorms upload.wikimedia.org Cumulonimbus Aerosol Clouds Nacreous Clouds Also known as “Mother of Pearl” Clouds Made of sulfuric acid (H2SO4) drops Formed in the stratosphere www.sflorg.com Nacreous Clouds Noctilucent Clouds Glows at night, observed as waves Made of parts of meteorites Formed in the mesosphere web.me.com Noctilucent Clouds Station Observation Maps Surface observation map http://aos.wisc.edu/weather/wx_obs/Surface.html Flash animation http://www.rap.ucar.edu/weather/surface/displaySfc.php?region =cod&endDate=20110123&endTime=-1&duration=24 Station Observations Cloud Cover Air Temperature Pressure Current Weather Dew Point Temperature Wind Speed & Direction • Temperature: 64 °F • Dew Point: 58 °F • Current Weather: Thin Fog • Cloud Cover: 75% Cloud Coverage - Broken • Pressure: 1002.7 mb • Wind Speed: 15 Knots (~7.5 m/s) • Wind Direction: Out of the South-East (Northwestward) Temperature Most scientists measure temperature (T) in Celsius (°C) or Kelvin (K) Current Weather Cloud Cover Pressure If less than 500 Place 10 on the left and divide by 10 Examples 027 becomes 1002.7 mb 184 becomes 1018.4 mb If greater than 500 Place 9 on the left and divide by 10 Examples 867 becomes 986.7 mb 642 becomes 964.2 mb Wind Speed & Direction Wind direction points in the direction that the wind is coming from (Ex: out of the SE) • 1 knot = 1.151 mph • 1 knot = 0.514 m/s Practice Online Examples Example 1 Example 2 Example 3 Example 4 Example 5 In-class Examples
