Total Air Temperature is a term used generally in aviation. It is the temperature measured approximately by a temperature probe mounted on the surface of the aircraft by or on the pitot intakes. It is higher than the static air temperature due to the translational energy of the molecules hitting the proble while the aircraft is in motion.
In summary, an aircraft in motion with a true airspeed will have a TAT greater (hotter) than the static air temperature by itself.
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