Rain gauge description and 10 uses
Answers
A rain gauge is a meteorological instrument to measure the precipitating rain in a given amount of time per unit area. The instrument consists of a collection container which is placed in an open area. The precipitation is measured in terms of the height of the precipitated water accumulated in the container per given time and is expressed in millimetres. Since the same amount of rain precipitation is assumed to be occurring around the container, the area of collection is not a factor. However, it should not be too small, neither should it be too large. Due to spatial uniformity of rainfall, 1 mm of measured precipitation is the equivalent of 1 L of precipitated rain water volume per metre squared.
A tipping bucket rain gauge consists of a pair of rainwater collecting buckets. It is covered by a funnel, with an open collector area at the top where A is the area of collection. The buckets are so placed on a pivot that only one bucket remains under the funnel at a time. During rain, rain water is collected in the collecting bucket, through the funnel. When the water fills up to a known point of the bucket, say having a volume v, the bucket tips, emptying the water. When one bucket tips, the other bucket quickly moves into place to collect rainwater. Each time a bucket tips, an electronic signal is sent to a recorder which is registered by the instrument with time stamp.
Rain gages have been designed as meteorological tools to measure the amount of typical precipitation (rain and snow) reaching the ground, unobstructed by surface effects.
The advantages of this type of gauge over tipping buckets are that it does not underestimate intense rain, and it can measure other forms of precipitation, including rain, hail and snow. These gauges are, however, more expensiveand require more maintenance than tipping bucket gauges.
Answer:
rain gauge is an instrument used by meteorologists and hydrologists to measure precipitation (e.g. rain, snow, hail or sleet) in a certain amount of time. It is usually measured in millimetres. Rain gauge is a meteorological instrument for determining the depth of precipitation (usually in mm) that occurs over a unit area (usually one metre square) and thus measuring rainfall amount. One millimetre of measured precipitation is the equivalent to one litre of rainfall per metre square.Usually a tapering funnel of copper or polyester of standard dimension allows the rain water to collect in an enclosed bottle or cylinder for subsequent measurement. The gauge is set in open ground with the funnel rim up to 30 cm above the ground surface. Some gauges are calibrated to allow the amount of rainfall to be read directly; with others it must be calculated from the depth of water in the container and the dimensions of the funnel.
The second type of rain gauge is the autographic gauge which can be either of the tilting-siphon type or the tipping-bucket type. The recording chart on an autographic rain gauge is mounted on a drum which is driven by clockwork and typically rotates round a vertical axis once per day. For a tilting-siphon rain gauge, the rainwater in a collector displaces a float so that a marking pen attached to the float makes a continuous trace on the paper. The two buckets in a tipping-bucket rain gauge rest on a pivot so that when one bucket has received 0.2 (or 0.5 mm) of rain it tips by gravity, empties the rainwater and allows the other bucket to start collection. During the tip, an electrical switch is closed and triggers a nearby autographic recorder to register each 'tilt', thus giving a fairly continuous record of precipitation and, in a more sophisticated form, even rainfall intensity. Rain gauges must be sited in as representative a location as possible, but the choice of location is difficult, since many precipitation events are highly aggregate. King Sejong the Great was the man who introduced rain gauge to the world. There are advantages and disadvantages of this instrument.