Instrument which measures rainfall

Anything under. This standard rain gauge is shown in the following figure. A rain gauge is an instrument that measures the amount of rainfall at a given time interval. In the more modern era, a common rain gauge is called the tipping bucket type. A bucket doesn't really tip? When one fills up with water, it tips and spills out, and the other comes into place to do the collecting.

These little funnels tip each time rainfall amounts to. The tip triggers a signal that is transmitted and recorded. Of course, these rain gauges have a problem when the temperature drops below freezing, so the standard versions are heated for the occasion. What about snowfall? When snow falls on these heated rain gauges, it melts, and a water equivalent is determined. The recorded precipitation is always expressed in terms of rainfall or melted snow.

The snow depth doesn't count? Sometimes a foot of snow amounts to just a half-inch of water, other times it amounts to three inches of water. Ceilometers can also be used to measure the aerosol concentration within the atmosphere.

A type of evaporation gauge or evaporimeter; it is a pan used in the measurement of the evaporation of water into the atmosphere over specified periods of time. An instrument used to measure the humidity, or amount of water vapour in the atmosphere.

The sensing mechanism of the instrument can be hair hair hygrometer , a plate coated with carbon electrical hygrometer , or an infrared sensor infrared hygrometer. A hygrometer composed of two similar thermometers. The bulb of one thermometer is kept wet by means of a thin, wet cloth wick so that the cooling that results from evaporation makes it register a lower temperature than the dry-bulb thermometer.

When readings are taken simultaneously, it is possible with the use of psychrometric tables to determine the relative humidity and dew-point temperature of the air. An instrument which records the environmental temperature and humidity at the same time, usually both continually. A standard shelter for housing four types of thermometers: dry, wet, maximum and minimum.

The screen shields the instruments from direct sunlight. A traditional thermometer consists of mercury, red spirit or green spirit in a glass tube and operates on the principle that the liquid expands more than the glass does when heated. Maximum temperature has historically been measured with a mercury-in-glass thermometer which has a constriction in the neck of the thermometer tube. As the air temperature rises mercury is forced past the constriction.

However, as the temperature falls the constriction prevents the mercury from returning to the bulb of the thermometer. The height of mercury in the tube remains at that reached at the hottest time of day. The thermometer is reset by gentle shaking. Alcohol-in-glass thermometers containing a moveable index are used to manually record minimum temperatures. When the temperature falls, the liquid and index move down the column, but when the temperature rises the index remains in the lowest position while the liquid expands up the tube.

The position of the index indicates the lowest temperature reached since the last reset - which is achieved by tilting the thermometer, bulb end upwards. When people refer to the temperature of the air they are normally referring to the dry bulb temperature.

The recording of rainfall using the standard or funnel rain gauge is generally done manually. These gauges work by catching the falling rain in a funnel-shaped collector that is attached to a measuring tube. The diameter of the collector is 10 times that of the tube; thus, the rain gauge works by magnifying the liquid by a factor of Magnifying the rain in this way allows precise measurements down to a one-hundredth of an inch.

Amounts that exceed the tube capacity are caught in the outer shell of the gauge, allowing the recorder to pour out the liquid in the tube and fill it back up if needed. The operation of a tipping bucket rain gauge is quite different from the standard gauge. The receiving funnel leads to one of two small buckets.

Filling of one bucket occurs at one-hundredth of an inch.