|
Читайте также: |
Anemometer
From Wikipedia, the free encyclopedia
Jump to: navigation, search
A hemispherical cup anemometer of the type invented in 1846 by John Thomas Romney Robinson
Cup-type anemometer with vertical axis, a sensor on a remote meteorological station deployed on Skagit Bay, Washington July–August, 2009.
An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind. The first known description of an anemometer was given by Leon Battista Alberti in around 1450[1].
Anemometers can be divided into two classes: those that measure the wind's speed, and those that measure the wind's pressure; but as there is a close connection between the pressure and the speed, an anemometer designed for one will give information about both.
A barometer is a scientific instrument used to measure atmospheric pressure. It can measure the pressure exerted by the atmosphere by using water, air, or mercury. Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs, high pressure systems, and frontal boundaries.
Barograph
Barogram of a heavy storm over northern Germany 2005
A barograph is a recording aneroid barometer. It produces a paper or foil chart called a barogram that records the barometric pressure over time.
Barographs use one or more aneroid cells acting through a gear or lever train to drive a recording arm that has at its extreme end either a scribe or a pen. A scribe records on smoked foil while a pen records on paper using ink, held in a knib. The recording material is mounted on a cylindrical drum which is rotated slowly by clockwork. Commonly, the drum makes one revolution per day, per week, or per month and the rotation rate can often be selected by the user.
Since the amount of movement that can be generated by a single aneroid is minuscule, up to seven aneroids (so called Vidie-cans) are often stacked "in series" to amplify their motion. It was invented in 1843 by the Frenchman Lucien Vidie (1805-1866).
As atmospheric pressure responds in a predictable manner to changes in altitude, barographs may be used to record elevation changes during an aircraft flight. Barographs were required by the FAI to record certain tasks and record attempts associated with sailplanes. A continuously varying trace indicated that the sailplane had not landed during a task, while measurements from a calibrated trace could be used to establish the completion of altitude tasks or the setting of records. Examples of FAI approved sailplane barographs included the Replogle mechanical drum barograph and the EW electronic barograph (which may be used in conjunction with GPS). Mechanical barographs are not commonly used for flight documentation now, having been displaced by GNSS Flight Recorders.
Hygrometers are instruments used for measuring relative humidity. A simple form of a hygrometer is specifically known as a psychrometer and consists of two thermometers, one of which includes a dry bulb and one of which includes a bulb that is kept wet to measure wet-bulb temperature. Modern electronic devices use temperature of condensation, changes in electrical resistance, and changes in electrical capacitance to measure humidity changes.
edit] Psychrometers
In a psychrometer, there are two thermometers, one with a dry bulb and one with a wet bulb. Evaporation from the wet bulb lowers the temperature, so that the wet-bulb thermometer usually shows a lower temperature than that of the dry-bulb thermometer, which measures dry-bulb temperature. When the air temperature is below freezing, however, the wet bulb is covered with a thin coating of ice and yet may be warmer than the dry bulb. Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer and the difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. Relative humidity can also be determined by locating the intersection of the wet- and dry-bulb temperatures on a psychrometric chart. One device that uses the wet/dry bulb method is the sling psychrometer, where the thermometers are attached to a handle or length of rope and spun around in the air for a few minutes.
A nephelometer [1] is stationary or portable instrument for measuring suspended particulates in a liquid or gas colloid. A Nephelometer measures suspended particulates by employing a light beam (source beam) and a light detector set to one side (often 90°) of the source beam. Particle density is then a function of the light reflected into the detector from the particles. To some extent, how much light reflects for a given density of particles is dependent upon properties of the particles such as their shape, color, and reflectivity. Nepheometers are calibrated to a known particulate, commonly Arizona road dust then use use environmental factors k-factors to compensate lighter or darker colored dusts accordingly. K-factor is determined by the user by running the Nephelometer next to an air sampling pump and comparing results.
Pan evaporation is a measurement that combines or integrates the effects of several climate elements: temperature, humidity, solar radiation, and wind. Evaporation is greatest on hot, windy, dry days; and is greatly reduced when air is cool, calm, and humid[1]. Pan evaporation measurements enable farmers and ranchers to understand how much water their crops will need.[2]
A pyranometer is a type of actinometer used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density (in watts per metre square) from a field of view of 180 degrees. The name pyranometer stems from Greek, "pyr - πῦρ" meaning "fire" and "ano - ἄνω" meaning "above, sky".
A typical pyranometer does not require any power to operate.
A radiosonde (Sonde is French for probe) is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required. A rawinsonde is a radiosonde that is designed to also measure wind speed and direction. Colloquially, rawinsondes are usually referred to as radiosondes.
Modern radiosondes measure or calculate the following variables:
Radiosondes measuring ozone concentration are known as ozonesondes.[1]
A rain gauge (also known as a udometer or a pluviometer [ Pluviograph ] or an ombrometer or a cup) is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation (solid precipitation is measured by a snow gauge) over a set period of time.
A snow gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of solid precipitation (as opposed to liquid precipitation that is measured by a rain gauge) over a set period of time.[ citation needed ]
The snow gauge consists of two parts, a copper catchment container and the funnel shaped gauge itself. The actual gauge is mounted on a pipe outdoors and is approximately 1.5 m (4 ft 11 in) high, while the container is 51.5 cm (201/4 in) long.
When snow has fallen the container is removed and replaced with a spare. The snow is then melted, while still in the container, and poured into a glass measuring graduate. While the depth of snow is normally measured in centimetres, the measurement of melted snow (water equivalent) is in millimetres. An estimate of the snow depth can be obtained by multiplying the water equivalent by ten.
The snow gauge suffers from the same problem as that of the rain gauge when conditions are windy. If the wind is strong enough, then the snow may be blown across the wind gauge and the amount of snow fallen will be under-reported. However, due to the shape and size of the funnel this is a minor problem.
If the wind is very strong and a blizzard occurs then extra snow may be blown into the gauge and the amount of snow fallen will be over-reported. In this case the observer must judge how much of the water is from snow blown into the container and how much is fallen snow.
Another problem that occurs, is when both snow and rain fall before the observer has time to change the gauge. In all of these cases the observer must judge how much of the water is snow and how much is rain.
SODAR (SOnic Detection And Ranging), also written as sodar, is a meteorological instrument also known as a wind profiler which measures the scattering of sound waves by atmospheric turbulence. SODAR systems are used to measure wind speed at various heights above the ground, and the thermodynamic structure of the lower layer of the atmosphere.
Sodar systems are like radar (radio detection and ranging) systems except that sound waves rather than radio waves are used for detection. Other names used for sodar systems include sounder, echosounder and acoustic radar.[1]
A sunshine recorder is a device that records the amount of sunshine at a given location. The results provide information about the weather and climate of a geographical area. This information is useful in meteorology, science, agriculture, tourism, and other fields.
There are two basic types of sunshine recorders. One type uses the sun itself as a times scale for the sunshine readings. The other type uses some form of clock for the time scale.
A Jordan sunshine recorder (left). The other instrument is a Marvin sunshine recorder.
Older recorders required a human observer to interpret the results; recorded results might differ among observers. Modern sunshine recorders use electronics and computers for precise data that do not depend on a human interpreter. Newer recorders can also measure the global and diffuse radiation.[ clarification needed ]
A weather radar, or weather surveillance radar (WSR), is a type of radar used to locate precipitation, calculate its motion, estimate its type (rain, snow, hail, etc.), and forecast its future position and intensity.
Modern weather radars are mostly pulse-Doppler radars, capable of detecting the motion of rain droplets in addition to intensity of the precipitation. Both types of data can be analyzed to determine the structure of storms and their potential to cause severe weather.
Дата добавления: 2015-10-24; просмотров: 94 | Нарушение авторских прав
| <== предыдущая страница | | | следующая страница ==> |
| Minimize Harm | | | Стоимость услуг |