<em>Barometers measure this pressure. ... Changes in the atmosphere, including changes in air pressure, affect the weather. Meteorologists use barometers to predict short-term changes in the weather. A rapid drop in atmospheric pressure means that a low-pressure system is arriving.</em>
This is the temperature indicated by a moistened thermometer bulb exposed to the air flow. The evaporation is reduced when the air contains more water vapor. The wet bulb temperature is always lower than the dry bulb temperature but will be identical with 100% relative humidity.
