Remote Sensing of Meteorological Variables

Remote Sensing






    Meteorological stations can record a plethora of variables depending on which sensors are available. At the simplest level, a meteorologist can step outside and look up to the skies, and record cloud cover. This is often done using a gridding method, to decide the percentage of cloud cover. The human eye can also judge colour and shape, allowing the classification of cloud type. Utilizing machines such as gear systems, light transmitters, receivers, pulleys and electrical devices, further information can be provided.

    Under the most strict definition, remote sensing requires the sensor to be spatially separate from the target study area. Utilizing telecommunication links, remote sensor stations can be constructed, and require no human interaction on site after installation. Remote sensor stations can be considered remote from user contact, and thereby fit under a loose definition of remote sensing. Multiple stations, spanning the globe, connected by telecommunications can provide global data values, but falls short because of its course resolution because of the distance between stations. Ground based platforms can have many sensors, to measure local meteorological variables, such as positional wind speed and direction, temperature, pressure, and many other variables. A wind vane is rotating object such as an arrow that shows direction of the wind because one side is larger and catches more wind. Using a cup anemometer, wind speed can be calculated by measuring the rate of rotation by a series of gears or voltage created by spinning an electric generator.

Pilot Balloon
    More true to the definition, a pilot balloon is a balloon is released and is visually tracked. The speed at which it ascends is known and the horizontal angle can be used to measure the direction of the wind, and the vertical angle can be converted to the distance traveled, which can give windspeed. A telescope, known as a theodolite, is used to manually track the balloon. (Miller et al., 1970)

    A transmissometer measures visibility by sending a known amount of light and receiving a portion of that light over a known distance. When an object, such as fog or snow gets between the projector and the detector, the amount of light received by the detector is translated to a reduced visibility level in terms of the average human eye's ability to be able to distinguish objects at a distance. (Miller et al., 1970)

Rotating Beam Ceilometer
    The projector is a high intensity rotating light source and is a known distance from the detector. The detector is oriented vertically, and when it detects the light source, the angle of the projector is recorded. Using trigonometry, the height of the cloud can be calculated for that moment. This instrument is often located at airports, as cloud height is very important for pilots know. (Miller et al., 1970)

Remote Sensing ~ Variables ~ Techniques ~ Sensors ~ Applications ~ References