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Temperature plays a major role in everyday life and also in meteorology. It indicates how hot or cold something is. You can measure the temperature with a thermometer. The temperature is usually indicated in the unit of measurement of degree Celsius.

An article by weather expert, weather columnist and meteorologist Roland Schmidt.

Temperature is an enormously important physical quantity for our bodily sensation. As living beings with a largely constant body temperature, we automatically react to outside temperatures that are too low or too high by shivering or sweating.

Since our well-being is therefore directly linked to the temperature, it is one of the basic ingredients of every weather forecast, which should really enable us to adjust to the external conditions in good time.

How can you measure the temperature?

Thermometers and devices with a temperature sensor from TFA measure the temperature for various purposes and display the values in degrees Celsius. Many TFA measuring instruments also offer the function of displaying the temperature in degrees Fahrenheit.

In meteorology, the science of all things related to the weather, air temperature plays a major role. That is why it is regularly measured under precisely specified conditions around the world.

Temperature measurement for weather observation

Measuring the temperature is one of the most important parts of weather observation. This is because water is the third main ingredient of our weather, along with the air and the sun. What’s important here:

Water changes its appearance according to the temperature. Firstly, as temperature rises, more and more water molecules change from a liquid to a gaseous state of aggregation and consequently become invisible to us (“water evaporates”).

Secondly, water generally reaches its freezing point at 0 degrees Celsius and so becomes solid. This also changes the precipitation that falls from the clouds: Rain becomes snow, sleet or hail.

But the special features of water are also linked to temperature: It already reaches its greatest density at the measured value of 4 degrees Celsius. Colder liquid water is nevertheless lighter and lies above warmer water that is 4 degrees Celsius. Water can be cooled in very fine droplet form to well below 0 degrees Celsius, which is of immense importance for precipitation formation in clouds. This is referred to as “supercooled water”.

What are the units of temperature?

In the measurement of temperature, three units have become established over time, all three of whose names stand for renowned physicists:

  • Celsius,
  • Fahrenheit and
  • Kelvin.

They were extensively involved in the development of temperature scales in the 18th and 19th centuries; other names, such as Reaumur, etc., have since fallen into disuse.

The unit of temperature commonly used for weather is Celsius. In this temperature scale, the boiling and freezing points of water are given as one hundred and zero degrees respectively.

The Kelvin scale works with the same graduation, but its zero point corresponds to the absolute lowest value of minus 273.15 degrees Celsius. On this so-called absolute temperature scale, the temperature cannot fall below the zero point.

The Fahrenheit scale, which is still used in Anglo-Saxon countries today, is somewhat more complicated: The temperature reading of 32 degrees Fahrenheit corresponds to 0 degrees Celsius, the reading of 100 degrees Celsius is 212 degrees Fahrenheit. So, the division into 100 degrees Celsius is contrasted with a corresponding one of 180 degrees Fahrenheit.

Tip: With the TFA conversion calculators, you can easily convert the temperature readings of the Celsius and Fahrenheit temperature scales.

How do you measure the temperature?

The decisive factor in weather observation of the temperature is above all the measuring point:

To guarantee international comparability, the temperature should always be determined in a shady, air-circulated place at a height of 2 metres. In addition, there should be a closely-cut grassy area under the measuring point and neither higher buildings nor high vegetation in the form of woody plants and trees should provide a “heat or cold sink effect” in the surrounding area.

For example, the maximum temperature for Germany of 42.6 degrees Celsius measured in Lingen in the Emsland region in July 2019 was subsequently declared invalid because unacceptably high vegetation had grown in the vicinity of the measuring station.

When installing a temperature sensor, make sure that it is never exposed to direct sunlight throughout the day – many maximum temperatures that are clearly too high have been recorded in this way.

In addition, there must be no walls in the immediate vicinity of the measuring point, which heat up strongly during the day due to direct sunlight. They emit the stored heat at night as long-wave radiation and thus prevent the measurement of a correct lowest temperature.

Moisture caused by rain or watering the garden must not affect the sensor either because evaporation of the water draws heat from the surroundings and consequently distorts the readings.

Temperature at ground level

In addition to the air temperature at a height of two metres that can be determined in this way, another temperature often plays an important role in everyday life: The Earth Minimum. Most of the change in air temperature occurs at ground level (assuming no change in air mass due to frontal passage).

During the day, the ground heats up due to the incident solar radiation and then releases this heat into the air; at night, the reverse process takes place. For example, the temperature drops significantly faster and more sharply directly above the ground than at a height of two metres; a ground minimum thermometer measures this effect at five centimetres above the ground.

All gardeners fear it because the difference between air and soil minimum may be two to three degrees. Although the weather forecast has predicted lows in the air temperature above zero degrees for the night, many sensitive plants have often been damaged by ground frost as a result.

What is temperature?

How can the concept of temperature be defined? The term temperature is used to describe a specific thermal state of a body or system. Temperature is an objective measure of how warm or cold an object is, e.g. air or water.

Temperature is a physical quantity expressed in various units of measurement: Kelvin, degrees Celsius, degrees Fahrenheit, degrees Rankine, degrees Delisle, degrees Newton, degrees Réaumur and degrees Rømer.

We monitor the temperature for weather trends, to check room temperature or to measure body temperature in the case of fever.

When preparing food, we concern ourselves with cooking chamber or core temperatures. When food or foodstuffs are stored and transported, measuring the temperature is important for maintaining the cold chain in order to comply with hygiene standards.

It may also be advisable to include a temperature reading for other products, such as alarm clocks, in order to keep a constant eye on the room temperature, for example.

Private households, companies, test centres and laboratories use thermometers to measure the temperature for various purposes.