The anemometer is used measure wind speed and direction. It is mounted on a mast of standard height of 30 feet (10 meters), and there should be no obstructions such as buildings or trees to deflect the wind from the anemometer. It should also be set absolutely vertical and to true north for an accurate wind direction indication. There are several types of anemometers;
This is the type most of us are familiar with. Modern ones have three cups and a vane at the tail to give wind speed and direction. A modern cup anemometer is shown below;
This instrument consists of a number of “Z” shaped sensors/transducers through which sonic pulses are transmitted and received. These pulses measure the wind speed very accurately, especially if numerous sensors are fitted, and because there are no moving parts maintenance is minimal. Most ultrasonic anemometers also have a tail vane to give wind direction. Some have heated sensor tips to keep them free from snow or ice thus ensuring accurate measurements. An Ultrasonic Anemometer is shown below;
5. Rain Gauges.
- Tipping Bucket Rain Gauge.
This gauge operates using two small buckets on a seesaw board. The rain collection funnel leads into the first bucket and once one hundredth of an inch is collected, the bucket tips the rainwater into a gauge. The funnel is then directed to the second bucket, and the process repeated. The tipping action sends a signal to the weather station that records the number of “tippings”. This is then multiplied by one hundredth of an inch to give the total rainfall over a given period.
The internal parts of a tipping bucket are shown below;
The modern tipping bucket rain gauge is digital but still works on the same principles.
This is the preferred rain gauge by many meteorologists as it is a very accurate means of rainfall measurement. This is due to the use of a vacuum that allows all the rainwater to enter the funnel and fall into the weighing mechanism and actual gauge. The amount of rainfall is then calculated from the weight. This also allows the amount of rainfall to be recorded by depth (inches) and weight (pounds) over a predetermined timescale.