Definition
The temperature of the air as measured by an ordinary thermometer whose sensing bulb is dry and shielded from direct radiation and moisture. It reflects the actual heat of the air without accounting for the cooling effect of evaporation.
Plain English
The plain temperature of the air, taken with a regular thermometer that has nothing wet on it.
Context Anchor
Seen in aviation weather study, humidity discussions, and aircraft performance planning where outside air temperature matters.
Derivation
Called 'dry-bulb' because it is paired with a 'wet-bulb' thermometer in a psychrometer. The wet-bulb has a damp wick around its sensing bulb, while the dry-bulb has none. Comparing the two readings reveals how much moisture is in the air.
Why Pilots Care
Used with dew point to determine humidity and density altitude, which affect engine performance and takeoff distance.
Analogy
It is like checking the room temperature with a normal dry thermometer, not one wrapped in a damp cloth.
Grounding Statement
Picture a thermometer sitting in the shade at the airport: the number it shows is the dry-bulb temperature.
Intuition Check
“Dry” does not mean the air itself has no moisture. It means the thermometer’s sensing end is dry when the temperature is measured.
Example Sentence 1
The METAR showed a dry-bulb temperature of 28 °C and a dew point of 26 °C, suggesting high humidity and a strong chance of fog by morning.
Example Sentence 2
The pilot compared the dry-bulb temperature and dew point to judge how much humidity would reduce climb performance.