Air temperature is the temperature of the atmosphere (air). One of the elements that make up the weather. It usually refers to the temperature of the air on the ground.
Only some languages such as Japanese and Chinese have a word that expresses only "temperature". Atmospheric temperature etc. are used.
Temperature measurements and statistics
When we think about weather and climate, the temperature is "ground temperature". Air temperature is measured by thermometers, but since there are several types of thermometers with different structures and characteristics of measured values, it is necessary to be careful when using measured values. The method of measuring the air temperature on the ground is specified by the World Meteorological Organization (WMO), and it is stipulated that the temperature should be measured at a height of 1.25 to 2.0 m above the ground, without exposing the thermometer directly to the outside air. In Japan, the Meteorological Agency defines the measurement height as 1.5m.
Usually, thermometers and hygrometers that require a similar measuring environment are placed in a ventilator with a fan or a centripetal box to meet the above measurement method.
If the thermometer gets wet due to intrusion of rain or condensation, or freezes due to intrusion of snow or frost, the latent heat absorption caused by evaporation or melting of water causes the temperature to drop, resulting in an error. Also, if the thermometer is exposed to direct sunlight or the flow of air around the thermometer is blocked, the temperature rises above the original ambient temperature, which also causes errors. In order to prevent this, the ventilation tube and the centripetal box have a structure that makes it difficult for rain and snow to enter. In order to reduce the influence of the heat generated by the fan, it is considered appropriate to provide a fan at the outlet of the outside air in the ventilation tube.
As for the installation environment of the ventilation tube and the centipede box containing the thermometer, the surrounding area should be well ventilated so that the temperature will be close to the original surrounding temperature, and the trees should be placed within a certain range to prevent the temperature from becoming unnecessarily low in the shade. It is desired that there are no heat sources in the surroundings so that the temperature does not become excessively high due to heating. The Japan Meteorological Agency's "Meteorological Observation Manual" stipulates that this should be done on open, level ground with no other obstacles such as trees or buildings nearby, on steep slopes or in depressions. should be avoided, but if installation is unavoidable, the characteristics should be understood by comparing with the ambient temperature. In addition, it is most desirable to use short grass for the ground (outdoor field) under the ventilator and the centipede box. there is On the other hand, materials such as asphalt, which is highly reflective, are considered unsuitable. It is said that the larger the area of the open field, the better, but at the Meteorological Agency's AMeDAS observatory, an open field of approximately 70m2 or more is secured.
Observations of air temperatures are also being carried out for use in weather forecasts. Radiosondes, in which temperature sensors are attached to rubber balloons and released into the sky, are most often used for fixed-time/fixed-point observations. The radiosonde passes through the troposphere and reaches up to about 30 km above the stratosphere. Airplanes also observe the temperature at any time and at fixed times, which is used for aviation weather.
In addition to the World Meteorological Organization, temperatures are expressed in degrees Celsius (°C) in many regions, including Japan, but in the United States, the traditional