Nebraskaland

14 Nebraskaland • December 2021 IN THE FIELD In recent years, I've heard a new term when listening to weather reports during summer — the "feels like" temperature. I'm not sure what precipitated the shift in nomenclature away from heat index, but I am personally not a fan of the weather conditions that result in its usage. This "feels like" measurement is designed to provide an apparent temperature that takes into account more than just the temperature of the air around you. How is this "feels like" temperature determined? The calculation uses both relative humidity and air temperature. As both of these values increase, human comfort decreases. Sometimes what may seem like a relatively modest air temperature of 90 degrees can seem downright oppressive if the atmosphere is moist, or sultry, as some early biometeorology researchers have phrased it. Our bodies take advantage of evaporative cooling through sweat, but humid conditions suppress its effectiveness. Exposure at certain categories of high heat feels like temperatures can lead to dangerous outcomes. For example, an index of 103 degrees or higher can cause heat exhaustion with prolonged exposure and/or physical activity. Temperature and humidity are two commonly observed parameters, although some weather stations also record solar radiation and wind. If this is the case, it is possible and more representative, in fact, to calculate a comprehensive climate index. Often used to determine cattle stress, it is a product of four different weather variables rather than two. Sunny and calm days drive up this climate index to indicate more uncomfortable conditions, while a breeze and overcast skies suppresses it. Even just a breath of wind can sometimes provide welcome relief and aid in evaporative cooling. When winter settles upon us, the "feels like" temperature switches to a different mode. Air temperature and wind speed are two of the most important factors that determine our comfort level. As temperatures take a dive and the wind kicks up, a wind chill temperature is determined and reported. This metric is based on the rate of heat loss from exposed skin. The higher the wind speed, the more heat that is lost, and the colder we feel. Even with an air temperature of zero, a wind speed of just 15 mph can result in frostbite in 30 minutes, with a "feels like" temperature of -19. This same cattle comfort index used to describe a summer "feels like" temperature also depicts the cold extremes. The weather observation network run by our climate office keeps tabs on these "feels like" temperatures all season long. If you are exposed to the elements for any length of time and you're feeling uncomfortable, be sure to check these "feels like" temperatures. Martha D. Shulski, at the University of Nebraska-Lincoln, is the director of the Nebraska State Climate Office. HOW DO YOU FEEL? By Martha D. Shulski The "feels like" temperature can be bearable for winter hunters when the wind is light. JEFF KURRUS, NEBRASKALAND

• Cover