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Surface Weather Observations (Worldwide, every 3 Hours GMT starting at 00:00) Current and past state of the weather e.g. Rain, Fog, etc. Air temperature Dry bulb temperature (Wet bulb temperature) Maximum, minimum temperatures. Surface Observations (continued).
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Surface Weather Observations (Worldwide, every 3 Hours GMT starting at 00:00) Current and past state of the weather e.g. Rain, Fog, etc. Air temperature Dry bulb temperature (Wet bulb temperature) Maximum, minimum temperatures
Surface Observations (continued) Relative humidity Amount and type of clouds Wind speed and direction Pressure, pressure tendency Precipitation
Psychrometers – Hygrometers Measure humidity and/or dew point Sling psychrometers use wet and dry bulb thermometers.
Clouds Aid in weather forecasting Trace atmospheric motions (e.g. satellite imagery) Produce precipitation Reflect sunlight away from Earth Absorb/emit heat radiation Absorb or rainout air pollution
Luke Howard (1772-1864) In 1803 introduced terminology for clouds based on their appearance, i.e. altitude, size, shape, and texture.
High-Level (> 20 kft) Ice crystals Cirrus (Ci) Cirrocumulus (Cc) Cirrostratus (Cs)
Mid-Level (6.5 to 20 kft) Mixed phase (i.e. water drops and ice crystals) Altocumulus (Ac) Altostratus (As)
Low-Level (up to 6500 ft) Water drops Cumulus (Cu) Stratocumulus (Sc) Stratus (St)
“Nimbo-” or “-nimbus” means cloud is producing precipitation. e.g. Cumulonimbus, Cb (thunderstorm) Nimbostratus, Ns (rain or snow)
Wind Vane or Weather Vane Measures direction wind is blowing FROM
Robinson cup anemometer (1795) Munro (1870)
Sonic anemometer Laser anemometer
Magdeburg hemispheres used to illustrate force produced by air pressure.
Water barometers Berti (1639) in Rome Guericke (c1654) in Magdeburg
In 1644, Torricelli wrote in a letter: "We live submerged at the bottom of an ocean of air."
Fortin (Mercury) Barometer
Weather glass or Thunder glass Used to measure CHANGES in atmospheric pressure (or temperature) "decreasing pressure predicts stormy weather"
Aneroid barometer – sealed metal case expands or contracts in response to variations in atmospheric pressure. High Low Levers magnify these changes, causing a pointer to move on a dial, or numbers to change on a digital read-out device.
Rain gauges measure depth of precipitation that occurred over a (known) area, or volume of rain per unit area Basic Gauge Tipping bucket and recorder gives time