What precautions are required to be taken while fixing a Rain Gauge?
What precautions are required to be taken while fixing a Rain Gauge?
Rain Gauge :A rain gauge (also known as an udometer, pluviometer, or an ombrometer) 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.Some precautions are required to be taken otherwise some errors can occurs in measurement and accuracy.
As the environment of the instrument’s location significantly influences observation of precipitation, the
surroundings must be considered when selecting the observation site.
(1) Conditions of Exposure
To ensure representative observation, the following environmental conditions should be considered
as far as possible:
-
The airflow around the rain gauge should be as horizontal as possible. Avoid sites that are
concave, elevated or tilted. Choose a site far from precipices or mountain ridges, where local
winds are strongly distorted. Avoid sites where wind blows through or stagnates. Building
rooftops should not be considered.
-
Choose sites away from other instruments, trees or buildings. Ideally, the instrument should be
installed at a distance from such objects equivalent to at least two to four times their height.
-
As the wind speed near the ground increases with height, the efficiency of precipitation
collection decreases the higher a gauge is placed. Accordingly, the receptacle should be placed
as low as possible. However, too low a setting will result in the entry of splashed rainwater
from the ground or the introduction of ground snow in the case of a snowstorm.
-
The ground surface around the rain gauge should be flat and covered with short grass (lawn) or
gravel to prevent raindrops from splashing into the unit from outside.
(2) Limitations of Accuracy
The most significant influences on the accuracy of precipitation measurement are the
environment and wind at the installation site rather than the performance of the instrument itself.
Such influences are difficult to eliminate. Additionally, because precipitation is strongly
characterized by locality, it is difficult to choose observation sites with a sufficient level of
representation. Site selection without such consideration may result in observations that have very
poor accuracy. It is strongly advisable to shield rain gauges from the wind or install them in an
optimum observation environment. Satisfying the installation condition will ensure
high accuracy of observation.
As the environment of the instrument’s location significantly influences observation of precipitation, the
surroundings must be considered when selecting the observation site.
(1) Conditions of Exposure
To ensure representative observation, the following environmental conditions should be considered as far as possible:
-
The airflow around the rain gauge should be as horizontal as possible. Avoid sites that are
concave, elevated or tilted. Choose a site far from precipices or mountain ridges, where local winds are strongly distorted. Avoid sites where wind blows through or stagnates. Building rooftops should not be considered.
-
Choose sites away from other instruments, trees or buildings. Ideally, the instrument should be installed at a distance from such objects equivalent to at least two to four times their height.
-
As the wind speed near the ground increases with height, the efficiency of precipitation collection decreases the higher a gauge is placed. Accordingly, the receptacle should be placed as low as possible. However, too low a setting will result in the entry of splashed rainwater from the ground or the introduction of ground snow in the case of a snowstorm.
-
The ground surface around the rain gauge should be flat and covered with short grass (lawn) or gravel to prevent raindrops from splashing into the unit from outside.
(2) Limitations of Accuracy
The most significant influences on the accuracy of precipitation measurement are theenvironment and wind at the installation site rather than the performance of the instrument itself. Such influences are difficult to eliminate. Additionally, because precipitation is strongly characterized by locality, it is difficult to choose observation sites with a sufficient level of representation. Site selection without such consideration may result in observations that have very poor accuracy. It is strongly advisable to shield rain gauges from the wind or install them in an optimum observation environment. Satisfying the installation condition will ensure high accuracy of observation.
