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A snow gauge is a type of instrument used by
meteorologist A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists in research, while t ...
s and
hydrologist Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
s to gather and measure the amount of solid
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...
(as opposed to liquid precipitation, which is measured by a
rain gauge A rain gauge (also known as udometer, pluvia metior, pluviometer, ombrometer, and hyetometer) is an instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a predefined area, over a period o ...
) over a set period of time.


History

The first use of snow gauges were precipitation gauges that was widely used in 1247 during the
Southern Song dynasty The Song dynasty (; ; 960–1279) was an imperial dynasty of China that began in 960 and lasted until 1279. The dynasty was founded by Emperor Taizu of Song following his usurpation of the throne of the Later Zhou. The Song conquered the res ...
to gather meteorological data. The Song Chinese mathematician and inventor Qin Jiushao records the use of gathering rain and snowfall measurements in the Song mathematical treatise '' Mathematical Treatise in Nine Sections''. The book discusses the use of large conical or barrel-shaped snow gauges made from bamboo situated in mountain passes and uplands, which are speculated to be first referenced to snow measurement.


Description

The snow gauge consists of two parts: a
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...
catchment A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
container; and the funnel-shaped gauge itself. The actual gauge is mounted on a pipe outdoors and is approximately in height, while the container is in length.


Measurement procedure

When
snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughou ...
is collected, the container is removed and replaced with a spare one. The snow is then melted while it is still in the container, and then 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 330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter. The millimetre (American and British English spelling differences#-re, -er, ...
. An estimate of the snow depth can be obtained by multiplying the water equivalent by a factor of 10. This multiplier can vary over a wide range, however, with many citing a range from 5 to 30, while the
National Snow and Ice Data Center The National Snow and Ice Data Center (NSIDC) is a United States information and referral center in support of polar and cryospheric research. NSIDC archives and distributes digital and analog snow and ice data and also maintains information abo ...
has quoted a range as wide as from 3 to 100. Any proposed factor depends on the water content of the snow (how "dry" it is), so this at best provides only a rough estimate of snow depth.


Issues

The snow gauge suffers from the same problem as that of the
rain gauge A rain gauge (also known as udometer, pluvia metior, pluviometer, ombrometer, and hyetometer) is an instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a predefined area, over a period o ...
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 occurs when both snow and
rain Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
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.


Other snow gauges


Automated

Remote reading gauges, such as used by weather stations, work similarly to rain gauges. They have a large catch area (such as a drum sawn in half, top to bottom) which collects snow until a given weight is collected. When this critical weight is reached, it tips and empties the snow catch. This dumping trips a switch, sending a signal. The collection then repeats. If the catch container has a heater in it, it measures the snow weight accurately. It is also possible to tip based on volume instead of weight, with appropriate fill sensing.


Snow pillow

Another snow sensor called a
snow pillow A snow pillow is a device for measuring snowpack, especially for automated reporting stations such as SNOTEL. The snow pillow measures the water equivalent of the snow pack based on hydrostatic pressure created by overlying snow. Any discrepancy ...
looks like a round bag lying on the ground. Inside the pillow is a liquid such as an environmentally safe
antifreeze An antifreeze is an additive which lowers the freezing point of a water-based liquid. An antifreeze mixture is used to achieve freezing-point depression for cold environments. Common antifreezes also increase the boiling point of the liquid, all ...
. Usually the snow pillow will be connected to a
manometer Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressu ...
. The manometer reading will vary based on how much snow is sitting on the pillow. This type of sensor works well for many locations but is more difficult to use in areas of hard blowing snow.


References


External links

{{Meteorological equipment Chinese inventions Meteorological instrumentation and equipment Snow Hydrology instrumentation