Bio Indexes

Heat Index

El �ndice de calor (HI) es un �ndice que combina la temperatura del aire y la humedad relativa, en �reas sombreadas, como un intento de determinar la temperatura equivalente percibida por los humanos, es decir, qu� tan caliente se sentir�a si la humedad fuera alg�n otro valor en la sombra. El �ndice de calor fue desarrollado en 1978 por George Winterling como "humiture" y adoptado por el Servicio Meteorol�gico Nacional de Estados Unidos un a�o despu�s. Se deriva del trabajo realizado por Robert G. Steadman. Al igual que el �ndice de sensaci�n t�rmica, el �ndice de calor contiene suposiciones sobre la masa y la altura del cuerpo humano, la ropa, la cantidad de actividad f�sica, el espesor de la sangre, la exposici�n a la luz solar y a la radiaci�n ultravioleta, y la velocidad del viento. Las desviaciones significativas de estos dar�n como resultado valores de �ndice de calor que no reflejan con precisi�n la temperatura percibida.

El �ndice de calor se define de manera que iguale la temperatura real del aire cuando la presi�n parcial del vapor de agua es igual a un valor de referencia de 1,6 kilopascales [kPa] (0,23 psi). A una presi�n atmosf�rica est�ndar (101,325 kPa), esta l�nea base corresponde a un punto de roc�o de 14 �C (57 �F) y una proporci�n de mezcla de 0,01 (10 g de vapor de agua por kilogramo de aire seco). Esto corresponde a una temperatura del aire de 25 �C (77 �F) y una humedad relativa del 50% en el mapa psicrom�trico del nivel del mar.

Summer Simmer Index

Summer Simmer Index provides a proven indicator of heat stress concerns and discomfort using meaningful equivalent temperature values for general public acceptance and awareness. Based on sound, scientific principles, it is confirmed by independent physiological models and backed up by hundreds of tests on human individual subjects. It is derived from studies by the American Society of Heating and Refrigeration Engineers (ASHRAE) and confirmed by tests and analyses done at Kansas State University. Unlike the index derived from those studies, however, it meets all subjective and objective requirements while relating to a dry environment. As such, the new SSI is the only temperature-humidity index that uses the results of proven physiological models and human tests and can be related to a dry environment for acceptance by the general public. By doing so the index, like the wind chill factor used during the winter, provides a meaningful and realistic temperature equivalent that can be used not only as an indication as to how hot it feels, but also as a readily identifiable warning for individuals subject to the physiological dangers of heat exposure.

Scharlau Winter Index

The Scharlau Winter Index has been established experimentally by K.Scharlau to asses cold exposure and measure the intensity of the human overcooling stress. The index is only valid if temperature is between -5 and +6�C (23 to 43�F) and humidity is above or equal to 40%. It reflects the feeling of discomfort due to radiative and evaporation heat losses from the exposed skin.

Scharlau Summer Index

The Scharlau Summer Index indicates the degree of thermal comfort or discomfort during the summer and higher temperatures. It is only defined in the temperature range between 17 and 39�C (63 to 102�F) and relative humidity above 30% (in the absence of wind).

Humidex

The humidex (humidity index) is an index number used by the Canadian meteorologists to describe how hot the weather feels to an average person as a result of the combined effect of heat and humidity. It is a dimensionless number calculated from the dew point.

The formula used to calculate it was developed by J.M.Masterton and F.A.Richardson of Canada's Atmospheric Environment Service in 1979. Unlike the heat index used in the United States, it is derived from dew point, rather than relative humidity.

Humidex above 40 is considered very high and in such conditions all unnecessary exposure and outdoor activity should be limited. If the reading is in the mid to high 30s, certain types of outdoor exercise should be reduced or modified, depending on the age and health of the individual, physical shape, type of clothes etc.

Relative Strain Index

The relative strain index (RSI) was developed by Lee and Henschel. It is also a measure of discomfort resulting from the combined effect of temperature and humidity. It assumes a person dressed in a light business suit, walking at a moderate pace in a very light air motion. It is applicable to assess heat stress of manual workers under shelter at various metabolic rates.

Thom's Discomfort Index (TDI)

Thom's Discomfort Index (TDI) indicates the level of discomfort as a result of high temperature and the combined effect with relative humidity. It was developed by E.C.Thom a researcher working at the U.S. Weather Bureau.