944mm 26/27 July : Rain measurement (pluviometer / udometer / rain guage)
What does "it rained 944 mm" mean ?
The basic measurement of rainfall is that of how much rain falls in a specified period of time. By how much, we mean the depth of rain accumulating on a level surface without soaking in, running away or evaporating. The depth is usually measured in millimetres. The standard periods are the hour, the day, the month and the year.
Since the required observation is that of the amount of rainfall, then the simplest way of obtaining this is to accumulate the rainfall in a container and measure the amount at the end of each day. The combination of a storage container and a device for measuring the amount of rain collected is usually called a storage gauge.
Why use a guage ? In answering this question we can partly explain why storage gauges are designed and operated the way they are. Suppose on a particular day some rain falls on the ground; why do we not just go out and measure the depth of the rain somewhere with, say, a ruler?
Consider what happens to rainwater when it falls on the ground. It collects in puddles, drains into gutters and streams, soaks into the ground and evaporates. It is quite possible for a puddle in a car park, which collects water from a large surrounding area, to have a depth ten times the depth of rain that fell. The area which drains into the puddle may be dry soon after the rain stops falling. Rain soaks into porous ground, such as fields, very quickly and leaves no accumulation to measure.
Obviously then, it is difficult to find a 'natural' place where an accurate representative measurement of depth of accumulated rainfall can be made with confidence. We use a gauge to overcome these problems.
Calibrations on the guage are representative of the area its supposed to cover. The guage is appropriately callibrated.
The Rain Guage. Also known as a pluviometer or a udometer.A rain gauge is a type of instrument used by meteorologists to gather and measure the amount of falling precipitation, rain.
The basic measurement of rainfall is that of how much rain falls in a specified period of time. By how much, we mean the depth of rain accumulating on a level surface without soaking in, running away or evaporating. The depth is usually measured in millimetres. The standard periods are the hour, the day, the month and the year.
Since the required observation is that of the amount of rainfall, then the simplest way of obtaining this is to accumulate the rainfall in a container and measure the amount at the end of each day. The combination of a storage container and a device for measuring the amount of rain collected is usually called a storage gauge.
Why use a guage ? In answering this question we can partly explain why storage gauges are designed and operated the way they are. Suppose on a particular day some rain falls on the ground; why do we not just go out and measure the depth of the rain somewhere with, say, a ruler?
Consider what happens to rainwater when it falls on the ground. It collects in puddles, drains into gutters and streams, soaks into the ground and evaporates. It is quite possible for a puddle in a car park, which collects water from a large surrounding area, to have a depth ten times the depth of rain that fell. The area which drains into the puddle may be dry soon after the rain stops falling. Rain soaks into porous ground, such as fields, very quickly and leaves no accumulation to measure.
Obviously then, it is difficult to find a 'natural' place where an accurate representative measurement of depth of accumulated rainfall can be made with confidence. We use a gauge to overcome these problems.
Calibrations on the guage are representative of the area its supposed to cover. The guage is appropriately callibrated.
The Rain Guage. Also known as a pluviometer or a udometer.A rain gauge is a type of instrument used by meteorologists to gather and measure the amount of falling precipitation, rain.
posted by Who's Blog - WGFA - CS | 3:45 AM
0 Comments:
Post a Comment
<< Home