Determining this specific temperature measurement involves understanding the interplay between air temperature and humidity. A common method employs a sling psychrometer, which consists of two thermometers: a dry-bulb thermometer measuring ambient air temperature and a wet-bulb thermometer, the bulb of which is covered with a water-soaked cloth. The instrument is then spun rapidly, causing evaporation from the wet cloth. This evaporation requires energy, which is drawn from the wet-bulb thermometer, causing its temperature to drop. The difference between the dry-bulb and wet-bulb readings, known as the wet-bulb depression, is then used in conjunction with psychrometric charts or equations to determine the desired value.
This measurement plays a critical role in assessing atmospheric conditions, especially related to human comfort and safety. It provides a more comprehensive understanding of heat stress than dry-bulb temperature alone, as it accounts for the cooling effect of evaporation. Historically, this method has been vital for industries ranging from agriculture and meteorology to HVAC system design and industrial processes where understanding the effects of humidity and temperature are essential for safety and efficiency. Furthermore, it remains a valuable tool in assessing the potential severity of heat waves and their impact on public health.