Remote Sensing of Meteorological Variables

Remote Sensing






Pilot Balloon

    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 wind speed. A telescope, known as a theodolite, is used to manually track the balloon.


    A radiosonde is a package of sensors and a radio transmitter, attached to a balloon and a parachute, were first used in 1938. When it is released, it provides a vertical profile of the atmosphere and a portion of the stratosphere as it travels to an altitude of 30km. During the ascent the sensors record the vertical distribution of temperature, humidity and pressure. A rawinsonde is a radiosonde that takes wind measurements. (met today, p13) A radiosonde can be tracked optically using a theodolite, by the reflection of radio waves using radar, or by tracking the radio signal transmitted. (Miller and Thompson, 1970) The payload box of instruments will fall to the ground under support of a parachute after the balloon bursts or a specific height or pressure is reached. Radiosondes are released twice daily, at 12 am and 12pm GWT from (#) sites worldwide.


    A dropsonde is a radiosonde dropped from an airplane.


    Pilots often report current positional atmospheric information such as cloud heights and weather phenomena which can be used for in-flight planning of other aircraft. Many sensors are used in aircraft, and provide better resolution for many phenomena due to being closer, decreasing the field of view.


    Rocketsondes travel to higher altitudes than radiosondes and provide a larger vertical profile. They are more costly than radiosondes and therefore are only released from less stations. At predetermined altitudes or pressures, they can release metal strips called chaff, which can be tracked by radar. Most rocketsondes release a sensor payload at a predetermined altitude or pressure and fall to earth by parachute. The sensor package records temperature, pressure and humidity, while ground based radar tracks its position and can be used to measure wind speed and direction. Most of the data on the way up is difficult to quantify and most reliable data comes from the decending phase of the launch.

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