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Measuring weather
remote observations
Now we move from in situ measurements to remote sensing observations. These are observations made at a distance, where the measuring device is away from what is being observed. We can remotely observe nearly any weather-describing variable at any location in the atmosphere; the surface can be observed from above, and the upper-air can be observed from below. A great benefit of remote observations is that you don't have to have people near the weather sample to make the measurement. Therefore, remote sensing observations are critical for the observation of remote regions, such as over the oceans, poles, deserts, and above the ground, where typically there aren't many trained human observers. They are also very good at viewing large areas of interest, rather than collections of a few points. Typically, remote sensing is accomplished by measurement of electromagnetic radiation, though sometimes other characteristics are observed, like sound waves. In either case, sensors are either passive, meaning that they simply detect signals already being emitted by samples, or they are active, meaning that they send out a signal pulse and measure whatever part of that pulse is reflected to the instrument.
Many of the most powerful remote observation platforms are large and very expensive like radar and satellite. However, some are small and cheap. Perhaps the
most accessible is the infrared radiation thermometer pictured to the right. IR
thermometers are passive remote sensors that sense thermal energy emitted by a
source object, like the sky or the ground. The warmer an object is, the
stronger it radiates. The IR thermometer's field of view expands conically
with distance from the instrument, and therefore the temperature it reads is an
average of what lies in the field of view, with a preference toward liquid and
solid matter, which radiate more strongly than the air. If you were to point an
IR thermometer at the clear sky, the temperature it observes will typically read
much less than freezing, since upper air temperatures are very low and make up a
great portion of the field of view.
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remote observations, radar
Links and resources
remote observations
Now we move from in situ measurements to remote sensing observations. These are observations made at a distance, where the measuring device is away from what is being observed. We can remotely observe nearly any weather-describing variable at any location in the atmosphere; the surface can be observed from above, and the upper-air can be observed from below. A great benefit of remote observations is that you don't have to have people near the weather sample to make the measurement. Therefore, remote sensing observations are critical for the observation of remote regions, such as over the oceans, poles, deserts, and above the ground, where typically there aren't many trained human observers. They are also very good at viewing large areas of interest, rather than collections of a few points. Typically, remote sensing is accomplished by measurement of electromagnetic radiation, though sometimes other characteristics are observed, like sound waves. In either case, sensors are either passive, meaning that they simply detect signals already being emitted by samples, or they are active, meaning that they send out a signal pulse and measure whatever part of that pulse is reflected to the instrument.
Many of the most powerful remote observation platforms are large and very expensive like radar and satellite. However, some are small and cheap. Perhaps the
most accessible is the infrared radiation thermometer pictured to the right. IR
thermometers are passive remote sensors that sense thermal energy emitted by a
source object, like the sky or the ground. The warmer an object is, the
stronger it radiates. The IR thermometer's field of view expands conically
with distance from the instrument, and therefore the temperature it reads is an
average of what lies in the field of view, with a preference toward liquid and
solid matter, which radiate more strongly than the air. If you were to point an
IR thermometer at the clear sky, the temperature it observes will typically read
much less than freezing, since upper air temperatures are very low and make up a
great portion of the field of view.
Next page
->
remote observations, radarLinks and resources
