A snow gauge is a type of instrument used by meteorologists

Meteorology

Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 and hydrologists to gather and measure the amount of solid precipitation

Precipitation (meteorology)

In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 (as opposed to liquid precipitation that is measured by a rain gauge

Rain gauge

A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time....

) over a set period of time.

The snow gauge consists of two parts, a copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 catchment

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 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

Snow

Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...

 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. However, this multiplier can vary over a wide range (many say the range is 5 to 30, but the National Snow and Ice Data Center

National Snow and Ice Data Center

The National Snow and Ice Data Center, or NSIDC, is a United States information and referral center in support of polar and cryospheric research...

 has quoted a range as wide as 3 to 100), depending on the water content of the snow (how "dry" it is), so this only provides, at best, a rough estimate of snow depth.

The snow gauge suffers from the same problem as that of the rain gauge

Rain gauge

A rain gauge is a type of instrument used by meteorologists and hydrologists to gather and measure the amount of liquid precipitation over a set period of time....

 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

Rain

Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

 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.

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.

Another snow sensor called a snow pillow

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...

 looks like a round bag lying on the ground. Inside the pillow is a liquid such as an environmentally safe antifreeze

Antifreeze

Antifreeze is a freeze preventive used in internal combustion engines and other heat transfer applications, such as HVAC chillers and solar water heaters....

. Usually the snow pillow will be connected to a manometer. 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.