Weather Instruments

The two most common thermometer scales in use are Fahrenheit and the Celsius scales. On Fahrenheit scale, the melting point of ice is 32°F and the boiling point of water is 212°F whereas on the Celsius scale, the melting and boiling points are 0°C and 100°C respectively. In India, the Celsius scale is used to measure temperature.

An aneroid barometer has a corrugated metal box which is made air tight by pumping air out of it and completely sealed. It has a thin flexible lid which is sensitive to changes of air pressure. The lid is pressed inward or outward as the air pressure increases or decreases respectively. The inward or outward movement of the lid moves a system of levers which is connected to a pointer. The pointer moves over the graduated dial to give the reading of the atmospheric pressure.

The unit used to measure wind speed is kilometres or knots per hour.
The arrow of the wind vane points to the direction from which the wind blows.

We can find the humidity in air by using Hygrometer or dry and wet bulb thermometer. It has two identical thermometers fixed on to a wooden frame. The bulb of one thermometer is kept uncovered. This is the dry bulb thermometer. The bulb of other thermometer is wrapped in a piece of wet cotton cloth. This is the wet bulb thermometer.
When the wind blows, water from the wet bulb thermometer evaporates and thus lowers the temperature. Hence, the wet bulb thermometer records a temperature lower than the dry bulb thermometer. The difference in the readings of the dry bulb thermometer and wet bulb thermometer helps us to find the humidity in the air. The lesser the difference, the more humid is the air.

If both the dry and the wet bulb thermometers show the same reading, it can be concluded that the air is fully saturated and the relative humidity is 100 percent.

On a map, the distribution of rainfall is shown using lines which join the places having the same amount of rainfall. Such lines are called isohyets. They are labelled with the rainfall values.

The meteorologists study weather.

Mercury is found inside a thermometer.

An anemometer is used to measure wind speed.

The dry bulb thermometer records a temperature higher than the wet bulb thermometer.

The measuring jar is used to measure the rainwater collected.

1. C
2. W
3. W
4. C
5. W

For accurate recording of temperature of free-moving air, the Six's thermometers are kept inside a Stevenson screen which is designed to allow the free movement of air through the box but protects the thermometers from the direct rays of the sun as it can affect the readings of thermometers.

The bulb of the wet bulb thermometer is always wrapped in a piece of wet cotton cloth so that when the wind blows, water from the wet bulb thermometer evaporates and thus lowers the temperature. Hence, the wet bulb thermometer records a temperature lower than the dry bulb thermometer. The difference in the readings of the dry bulb thermometer and wet bulb thermometer helps us to find the humidity in the air. The lesser the difference, the more humid is the air.

The study of weather through careful observation, measurement and recording of the conditions of the various elements of the weather is called meteorology.

Fahrenheit and Celsius scales are used to measure temperature.

False

Corrected statement — The Six's maximum and minimum thermometers are kept inside a Stevenson screen.

Isotherms connect places having equal temperature.

Millibar is the unit used to measure atmospheric pressure.

Weather station

Stevenson screen

Barograph

Hygrometer or wet and dry thermometer

Millimetres