Observations and Station Models AOS 101 Discussion Sections 302 and 303

Observations  What do we mean by observations?  Collecting data through various instruments  Importance of observations  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  Air temperature  Dew point temperature  Air pressure  Humidity  Wind speed and direction  Cloud cover  Ocean salinity  Etc… farm4.static.flickr.com

Air Temperature  Air temperature is measured by a thermometer

Dew Point Temperature  Dew point temperature  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  The wet-bulb temperature is reached when the air temperature is high enough to evaporate the water from the cloth  A simpler way to think of it  The temperature you feel when your arm is exposed to moving air  Can also be measured by a psychrometer

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

Wind Speed and Direction  Wind speed is measured by an anemometer  Weather vanes and wind socks tells us wind direction

Air Pollution  The concentration of pollutants can be measured by an aerosol monitor windows2universe.org blog.lib.umn.edu

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  Radio – radio transmitter  Sonde – messenger in Old English  What does it measure?  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!

Radiosonde Instrumentation  Thermistor (Temperature)  Hygristor (Humidity)  Can be used to find dew point  Aneroid Barometer (Pressure)  Can be used to detect different atmospheric layers  Radio Transmitter & GPS  Balloon & Parachute  Radiosondes cost approximately $300 and most of the time the instruments are never found artemis.rsmas.miami.edu

Sounding Diagram rap.ucar.edu

Main Cloud Name Elements  Alto  High  Cirrus  Thin and wispy  Cumulus  Fluffy  Nimbus  Raincloud  Stratus  Layer or spread- out

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 Stratus upload.wikimedia.org 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 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 Altostratus Altocumulus upload.wikimedia.org

High-Level Clouds  Cirrostratus  Occurs when moist air cools to saturation at a high altitude  Made of ice crystals  Cirrocumulus  Same as cirrostratus, but has convective instability  Cirrus  Happens at the highest part of the tropopause  Usually means a storm is approaching mw2.google.com Cirrostratus upload.wikimedia.org Cirrocumulus 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 (H 2 SO 4 ) drops  Formed in the stratosphere  Noctilucent Clouds  Glows at night, observed as waves  Made of parts of meteorites  Formed in the mesosphere Nacreous Clouds Noctilucent Clouds web.me.com

Station Observation Maps  Surface observation map   Flash animation  =cod&endDate= &endTime=-1&duration=24 =cod&endDate= &endTime=-1&duration=24

Station Observations Air Temperature Dew Point Temperature Current Weather Cloud Cover Pressure Wind Speed & Direction Cloud Cover: 75% Cloud Coverage - Broken Pressure: mb Wind Speed: 15 Knots (~7.5 m/s) Wind Direction: Out of the South-East (Northwestward) Temperature: 64 °F Dew Point: 58 °F Current Weather: Thin Fog

 Most scientists measure temperature (T) in Celsius (°C) or Kelvin (K) Temperature

Current Weather

Cloud Cover

Pressure  If less than 500  Place 10 on the left and divide by 10  Examples  027 becomes mb  184 becomes mb  If greater than 500  Place 9 on the left and divide by 10  Examples  867 becomes mb  642 becomes mb

Wind Speed & Direction  Wind direction points in the direction that the wind is coming from (Ex: out of the SE) 1 knot = mph 1 knot = m/s

Practice  Online Examples  Example 1 Example 1  Example 2 Example 2  Example 3 Example 3  Example 4 Example 4  Example 5 Example 5  In-class Examples