The Use of the Hygrometer as a Weather Instrument
for Home Weather Forecasting
for Home Weather Forecasting
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The accurate measure of humidity, in basic weather forecasting, is one of the most difficulty problems meteorologists face. The weather instrument that does the measuring of this weather characteristic is known as a "hygrometer."
One type of hygrometer that measures relative humidity is called a psychometer. This instrument is made from two separate thermometers. One thermometer bulb is placed in a quantity of water while the other bulb is held in the air, untouched by the water. A temperature reading is taken from each of these thermometers and the difference between them is the "relative humidity." The process is, in actuality, not as simple as this but this is a basic example furnished so that the reader will have some idea of how the psychrometer actually works.
The reason that the humidity reading is so difficulty to achieve is because of the many internal variables that occur due to the various unintended changes. For instance, the water bulb is immersed in a solution (water) that has minute variances in different levels or currents of the water. In order to avoid this, the water must be constantly stirred so that it maintains a near constant temperature throughout. Other problems develop when the ambient temperatures are below freezing and thus different methods of controlling the instruments are developed. More information can be acquired simply by performing an online search for the word "hygrometer."
Hygrometers are often used in public saunas, in cigar humidors and in museums. Humidity is a characteristic that can either enhance or destroy a material, depending on its sensitivity to the humidity in the air. With the aid of these humidity detectors, it is possible to control the amount of water vapor within confined spaces.
The specific temperature at which moistened air reaches what is known as water vapor saturation is called the "dewpoint." The air must be at a constant temperature in order for the measurement to be accurate. When the air reaches the saturation temperature, any additional cooling of it will result in the water condensing.
There are what is known as "cooled mirror dewpoint hygrometers." As far as relative humidity goes, these are considered the most precision instruments for measuring it. The method used in these particular instruments is that of using a mirror that has been chilled. The actual temperature of the mirror can be controlled by a computer program and it moves the temperature warmer or cooler by very small increments. When microscopic amounts of water vapor are detected by the optoelectronic monitors, the instrument can then determine that this is the exact dew point. As you can imagine, this is a very delicate and expensive instrument.
For the home weather station enthusiast, hygrometers can often be found in some home weather station. They can also be located as separate weather instrument components. One brand of hygrometer as a separate component is the Honeywell TM005X Wireless Indoor/Outdoor Thermo-Hygrometer
Many hygrometer models are found as combination with other weather instruments. They can often be found with indoor outdoor thermometers, rain gauges, barometers, atomic clocks, compasses or with anemometer interfaces.
The US Weather Service even has weather maps available with relative humidity markings available for local, regional or larger areas. Obviously, these maps are possible because of the very precise and accurate hygrometers furnished by the weather service. Keep in mind that the relative humidity changes as quickly as the temperature,so maps are often inaccurate moments after they are produced.
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