The Heat Index can be useful for calculating the dangers related to medical issues such as muscle cramping, dehydration, heat exhaustion, or the more serious heatstroke on hot and humid days. The apparent temperature is often described as how hot it feels to the human body. When relative humidity is high, it becomes increasingly difficult for the body's sweat to evaporate, leaving individuals without an effective natural way to cool off. Maps of heat advisories or warnings are often a product of reclassifying the heat index result into buckets. The higher the index value, the more likely it is to become a warning rather than an advisory.
The formula the function uses to compute heat index is as follows:
Output Heat Index = (-42.379 + (2.04901523 * T) + (10.14333127 * R) - (0.22475541 * TR) - (6.83783e-3 * TT) - (5.481717e-2 * RR) + (1.22874e-3 * TTR) + (8.5282e-4 * TRR) - (1.99e-6 * TTRR))
- T = Air temperature
- R = Relative humidity
Temperature Raster: A single-band raster where pixel values represent ambient air temperature.
Temperature Units: The unit of measurement associated with the input temperature raster. Available input units are as follows:
Relative Humidity Raster: A single-band raster where pixel values represent relative humidity as a percentage value between 0 and 100.
Heat Index Units: The unit of measurement associated with the output heat index. Available units are as follows:
Steadman, Robert G. "The Assessment of Sultriness. Part I: A Temperature-Humidity Index Based on Human Physiology and Clothing Science." Journal of Applied Meteorology 18.7 (1979): 861–873.
Steadman, Robert G. "The Assessment of Sultriness. Part II: Effects of Wind, Extra Radiation and Barometric Pressure on Apparent Temperature." Journal of Applied Meteorology 18.7 (1979): 874–885.
National Weather Service. "NWS Heat Index." http://www.nws.noaa.gov/om/heat/heat_index.shtml.