2002 Annual

Wednesday, 16 January 2002
A New Year-round Multivariable Comfort Index
Ken Reeves, AccuWeather, Inc., State College, PA; and M. Steinberg
There are a number of indices that describe the effects of other weather parameters upon how a particular ambient temperature feels, and the effects it has on the health and safety of a person. Indices such as Wind Chill, Apparent Temperature, Heat Index and Humiture each include only one element in addition to temperature, either wind speed or a measure of humidity. Each of these indices is therefore limited in two ways: First, because of their nature, they are each only of value in either hot or cold weather, and are therefore not suitable for year-round use in temperate climates. Second, because they each include only two parameters, they do not accurately portray how the weather feels and effects human activity.

We recognize from experience that multiple parameters play a role in how hot or cold it feels at a particular temperature. For example, while Apparent Temperature is based only upon ambient temperature and humidity, personal experience tells us that a variety of factors, such as solar intensity and the presence (or absence) of a breeze also play a role in the level of discomfort we feel during hot weather, and the level of hazard to a person during outdoor activities.

The RealFeel Temperature (tm) is a new index, created utilizing heat flux equations with regard to an appropriately clothed person, and truthed using study groups that examined both meteorological assessments and people's perceptions of the effects of a variety of parameters on how hot or cold it feels to a person, based upon temperature and a variety of weather and other parameters.

It incorporates all of the weather factors that play a role in how a given weather situation feels to an appropriately clothed person, and can therefore be used as a guide to appropriate outdoor activities and safety precautions. Included in the calculation of RealFeel Temperature are ambient temperature, dew point, wind speed, atmospheric pressure and type and intensity of precipitation. Also included is solar intensity, which is derived utilizing latitude, date, time of day, elevation, visibility, precipitation type and intensity, cloud coverage, cloud types and cloud thickness.

Because it is designed to incorporate all relevant weather parameters, the RealFeel Temperature is also appropriate for year-round use, in all climates.

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