Weather instruments

Junior Certificate Geography Notes on Weather Instruments and Weather forecasting for the Irish Second Level Education Curriculum

1. Weather Instruments
Weather Instruments
The main elements of the weather that are measured are-
 Temperature
 Wind (Direction and Speed)
 Humidity
 Precipitation
 Sunshine
Different instruments are used to measure these different elements of the weather.
These are-
Thermometer (Used to measure temperature)
Temperature can be measured in Degrees Celsius and also in Fahrenheit.
Thermometers have a bulb at the bottom that is full of Mercury or Alcohol. The
mercury rises or falls depending on the temperature.

2. A thermometer with alcohol that rises and falls in the glass tube
Stevenson’s Screen
Weather stations record the temperature in the shade, using a Stevenson’s screen. It
contains TWO thermometers, one to record the highest temperature and the other to
record the lowest. They then take the average.
To record the Average temperature. Add up all the temperatures of each month and divide by
the number of months.
To find the Range of temperature. Take the lowest from the highest.

3. A Stevenson’s Screen that measures temperature and humidity
Wind
Two elements are measured. Wind direction and wind speed.
Wind direction
Wind direction is measured with a Wind Vane.If the arrow is pointing to the north, that
means it is a Northerly Wind. Winds get their name from the direction they come
from. Prevailing winds are winds that are most common to an area. Ireland’s prevailing
winds are the South-Westerlies.

A Wind Vane that shows direction
Wind Speed
Wind speed is measured using an instrument called an anemometer. The Anemometer has
little cups on it that rotate when the wind blows. The faster the wind blows the faster the cups
turn.

4. An Anemometer that calculates wind speed
Rain Gauge
A rain gauge calculates the amount of rain that falls by collecting it in a graduated cylinder.
The rain gauge must be left out in the open, above the ground and away from any form of
shelter.

A Rain Gauge