]> The lowering of temperature during night time, due to a net loss of radiant energy. In meteorology, the result of radiative cooling of the earth's surface and adjacent air. Radiational cooling occurs, as is typical on calm, clear nights The temperature to which a given air parcel must be cooled at constant pressure and constant water vapor content in order for saturation to occur. The temperature at which motionless saturated air would induce, in a sedentary worker wearing ordinary indoor clothing, the same sensation of comfort as that induced by the actual conditions of temperature, humidity, and air movement. Effective temperature is used as a guide in air-conditioning practice, and, on the comfort chart (American Society of Heating and Air Conditioning Engineers), it appears as a family of curves that serves as one coordinate in defining comfort zones. A means of quantifying the threat of rapid cooling during breezy or windy conditions that may result in hypothermia in cold conditions.