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Modified physiologically equivalent temperature—basics and applications for western European climate

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Abstract

A new thermal index, the modified physiologically equivalent temperature (mPET) has been developed for universal application in different climate zones. The mPET has been improved against the weaknesses of the original physiologically equivalent temperature (PET) by enhancing evaluation of the humidity and clothing variability. The principles of mPET and differences between original PET and mPET are introduced and discussed in this study. Furthermore, this study has also evidenced the usability of mPET with climatic data in Freiburg, which is located in Western Europe. Comparisons of PET, mPET, and Universal Thermal Climate Index (UTCI) have shown that mPET gives a more realistic estimation of human thermal sensation than the other two thermal indices (PET, UTCI) for the thermal conditions in Freiburg. Additionally, a comparison of physiological parameters between mPET model and PET model (Munich Energy Balance Model for Individual, namely MEMI) is proposed. The core temperatures and skin temperatures of PET model vary more violently to a low temperature during cold stress than the mPET model. It can be regarded as that the mPET model gives a more realistic core temperature and mean skin temperature than the PET model. Statistical regression analysis of mPET based on the air temperature, mean radiant temperature, vapor pressure, and wind speed has been carried out. The R square (0.995) has shown a well co-relationship between human biometeorological factors and mPET. The regression coefficient of each factor represents the influence of the each factor on changing mPET (i.e., ±1 °C of T a = ± 0.54 °C of mPET). The first-order regression has been considered predicting a more realistic estimation of mPET at Freiburg during 2003 than the other higher order regression model, because the predicted mPET from the first-order regression has less difference from mPET calculated from measurement data. Statistic tests recognize that mPET can effectively evaluate the influences of all human biometeorological factors on thermal environments. Moreover, a first-order regression function can also predict the thermal evaluations of the mPET by using human biometeorological factors in Freiburg.

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Authors and Affiliations

  1. Albert-Ludwigs-University Freiburg, Fahnenbergplatz, 79085, Freiburg, Germany

    Yung-Chang Chen & Andreas Matzarakis

  2. Research Center for Environmental Changes, Academia SINICA, No.128, Section 2, Academia Road, Nankang, Taipei, 11529, Taiwan

    Yung-Chang Chen

  3. Centre for Human Biometeorological Research, Deutscher Wetterdienst, Stefan-Meier-Str. 4, 79104, Freiburg, Germany

    Andreas Matzarakis

Authors
  1. Yung-Chang Chen
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  2. Andreas Matzarakis
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Correspondence to Yung-Chang Chen.

Appendix

Appendix

Symbol lists

c Heat capacity of a body tissue (J/(kg*K))

c bl Heat capacity of blood (J/(kg*K))

k Conductive coefficient of tissue (w/(m*K))

Q e , sk Sensible heat flux over skin (W/m2)

Q e , sk Evaporative heat flux over skin (W/m2)

q m Metabolic rate of tissue (W/m3)

R c , cl , total Conductive resistance of the total garments (w/(m2*K))

R c , cl , 1 Conductive resistance of the inner garments (w/(m2*K))

R e , cl , total Vapor pressure resistance of the total garments (w/(m2*hPa))

R e , cl , 1 Vapor pressure resistance of the inner garment (w/(m2*hPa))

RHRelative humidity (%)

r Radius of tissue (m)

T a Air temperature (°C)

T bl , a Temperature of arterial blood (°C)

T cl,1 Clothing temperature of the inner garment (°C)

T cor Core temperature (°C)

T mrt Mean radiant temperature (°C)

T sk Skin temperature (°C)

T t Temperature of tissue (°C)

t Time step (s)

VPAir vapor pressure (hPa)

VP sk Skin surface vapor pressure (hPa)

VP cl, 1 Vapor pressure of the inner clothing (hPa)

vWind speed (m/s)

w bl Perfusing rate of blood (1/s)

ρ Tissue density (kg/m3)

ρ bl Blood density (kg/m3)

ω Geometric coefficient of tissue (ω = 1 by a cylinder; ω = 2 by a sphere).

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Chen, YC., Matzarakis, A. Modified physiologically equivalent temperature—basics and applications for western European climate. Theor Appl Climatol 132, 1275–1289 (2018). https://doi.org/10.1007/s00704-017-2158-x

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  • DOI: https://doi.org/10.1007/s00704-017-2158-x

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