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The development of the Hong Kong Heat Index for enhancing the heat stress information service of the Hong Kong Observatory


This paper presents a study to develop a heat index, for use in hot and humid sub-tropical climate in Hong Kong. The study made use of hospitalization data and heat stress measurement data in Hong Kong from 2007 to 2011. The heat index, which is called Hong Kong Heat Index (HKHI), is calculated from the natural wet bulb temperature, the globe temperature, and the dry bulb temperature together with a set of coefficients applicable to the high humidity condition in the summer of Hong Kong. Analysis of the response of hospitalization rate to variation in HKHI and two other heat indices, namely Wet Bulb Globe Temperature (WBGT) and Net Effective Temperature (NET), revealed that HKHI performed generally better than WBGT and NET in reflecting the heat stress impact on excess hospitalization ratio in Hong Kong. Based on the study results, two reference criteria of HKHI were identified to establish a two-tier approach for the enhancement of the heat stress information service in Hong Kong.

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  1. Beniston M, Diaz HF (2004) The 2003 heat wave as an example of summers in a greenhouse climate? Observations and climate model simulations. Glob Planet Chang 44:73–81

    Article  Google Scholar 

  2. Budd GM (2008) Wet-bulb globe temperature (WBGT)—its history and its limitations. J Sci Med Sport 11:20–32

    Article  Google Scholar 

  3. Chan EYY, Goggins WB, Kim JJ, Griffiths SM (2011) Help-seeking behavior during elevated temperature in Chinese population. J Urban Health 88(4):637–650

    Article  Google Scholar 

  4. Chan HS, Kok MH, Lee TC (2012a) Temperature trends in Hong Kong from a seasonal perspective. Clim Res 55:53–63

    Article  Google Scholar 

  5. Chan EYY, Goggins WB, Kim JJ, Griffiths SM (2012b) A study of intracity variation of temperature-related mortality and socioeconomic status among the Chinese population in Hong Kong. J Epidemiol Community Health 66(4):322–327

    Article  Google Scholar 

  6. Chan EYY, Goggins WB, Yue JSK, Lee P (2013) Hospital admission as a function of temperature, other weather phenomena and pollution levels in an urban setting in China. Bull World Health Organ 91:576–584

    Article  Google Scholar 

  7. Claassen N, Kok R (2007) The accuracy of the WBGT heat stress index at low and high humidity levels. Occup Health South Afr 13(2):12–18

    Google Scholar 

  8. D’Ambrosio Alfano FR, Malchaire J, Palella BI, Riccio G (2014) WBGT index revisited after 60 years of use. Ann Occup Hyg 58(8):955–970

    Article  Google Scholar 

  9. DeGaetano A, Allen AJ, Gallo KP (2002) A homogenized historical temperature extreme dataset for the United States. J Atmos Ocean Technol 19:1267–1283

    Article  Google Scholar 

  10. D’Ippoliti D, Michelozzi P, Marino C, de‘Donato F, Menne B, Katsouyanni K, Kirchmayer U, Analitis A, Medina-Ramón M, Paldy A, Atkinson R, Kovats S, Bisanti L, Schneider A, Lefranc A, Iñiguez C, Perucci CA (2010) The impact of heat waves on mortality in 9 European cities: results from the EuroHEAT project. Environ Heal 9:37. doi:10.1186/1476-069X-9-37

    Article  Google Scholar 

  11. Ginn WL, Lee TC, Chan KY (2010) Past and future changes in the climate of Hong Kong. Acta Meteor Sinica 24(2):163–175 (English Edition).

  12. Goggins WB, Chan EYY, Ng E, Ren C, Chen L (2012) Effect modification of the association between short-term meteorological factors and mortality by urban heat islands in Hong Kong. PLoS ONE 7(6):e38551. doi:10.1371/journal.pone.0038551

    CAS  Article  Google Scholar 

  13. Goggins WB, Chan EYY, Yang CY, Chong M (2013) Associations between mortality and meteorological and pollutant variables during the cool season in two Asian cities with sub-tropical climates: Hong Kong and Taipei. Environ Heal 12:59

    CAS  Article  Google Scholar 

  14. Goldman RF, Green EB, Iampietro PF (1965) Tolerance of hot, wet environments by resting men. J Appl Physiol 20(2):271–277

    Google Scholar 

  15. Hong Kong Observatory (2014) Statistics of special weather events in Hong Kong.

  16. Hong Kong Observatory (2015) Cold and very hot weather warnings.

  17. ISO 7243 (1989) Hot environments—estimation of the heat stress on working man, based on the WBGT index

  18. Jeffcott L, Leung WM, Riggs C (2009) Managing the effects of the weather on the Equestrian events of the 2008 Beijing Olympic Games. Vet J 182(3):412–429

    Article  Google Scholar 

  19. Kerslake MKD (1972) The stress of hot environments. University Press, Cambridge

    Google Scholar 

  20. Kjellstrom T, Kovats RS, Lloyd SJ, Holt T, Tol RSJ (2009) The direct impact of climate change on regional labor productivity. Arch Environ Occup Health 64:217–227

    Article  Google Scholar 

  21. Kuwabara K, Mochida T, Sakoi T (2007) Derivation and analysis of the outdoor Wet Bulb Globe Temperature (WBGT) with a human thermal engineering approach—part 2. Properties of the WBGT formula for outdoor activities with solar radiation. Proceedings of Clima 2007 Well-being indoors

  22. Lam CY (2006) On climate changes brought about by urban living. Hong Kong Meteorological Society Bulletin, Vol 16, Number 1/2, 2006

  23. Lee TC, Chan KY, Ginn EWL (2011) Projections of extreme temperature events in Hong Kong in the 21st century. Acta Meteor Sin (Engl Ed) 25(1):1–20

    Article  Google Scholar 

  24. Li PW, Chan ST (2000) Application of a weather stress index for alerting the public to stressful weather in Hong Kong. Meteorol Appl 7(4):369–375

    CAS  Article  Google Scholar 

  25. Lin S, Hsu W, Van Zutphen AR, Saha S, Luber G, Hwang SA (2012) Excessive heat and respiratory hospitalizations in New York State: estimating current and future public health burden related to climate change. Environ Health Perspect.

  26. Macpherson RK (1960) Physiological responses to hot environments. An account of work done in Singapore, 1948–1953, at the Royal Naval Tropical Research Unit, with an appendix on preliminary work done at the National Hospital for Nervous Diseases, London. London, Her Majesty’s Stationery Office

  27. Minard D (1964) Effective temperature scale and its modifications. Research Report No. 6. Naval Medical Research Institute, Bethesda

  28. Mok HY, Leung B (2009) The impact of cold and hot weather on senior citizens in Hong Kong. Hong Kong Meteorological Society Bulletin, Vol 19 (2009) August 2011

  29. Moran DS, Shapiro Y, Epstein Y, Matthew W, Pandolf KB (1998) A modified discomfort index (MDI) as an alternative to the wet bulb globe temperature (WBGT). In: Hodgdon JA, Heaney JH, Buono MJ (eds) Environmental ergonomics VIII. Int Conf Environ Ergo, San Diego, pp 77–80

    Google Scholar 

  30. Ramanathan NL, Belding HS (1973) Physiological evaluation of the WBGT index for occupational heat stress. Am Ind Hyg Assoc J 34:375–383

    CAS  Article  Google Scholar 

  31. Van Zutphen AR, Lin S, Fletcher BA, Hwang S (2012) A population-based case–control study of extreme summer temperature and birth defects. Environ Health Perspect 120(10):1443–1449

    Article  Google Scholar 

  32. Willett KM, Sherwood S (2012) Exceedance of heat index thresholds for 15 Regions under a warming climate using the wet-bulb globe temperature. Int J Climatol 32:161–177

    Article  Google Scholar 

  33. Wong TK, Lee TC (2008) Heat stress analysis related to the 2008 Olympic Equestrian events in Hong Kong. Guangdong-Hong Kong-Macau Seminar on Meteorological Science and Technology, Zhongshan, China, 21–23 January 2008 (in Chinese only)

  34. Wong MC, Mok HY, Lee TC (2011) Observed changes in extreme weather indices in Hong Kong. Int J Climatol 31:2300–2311. doi:10.1002/joc.2238

    Article  Google Scholar 

  35. Wong HT, Chiu YL, Wu ST, Lee TC, SCHSA (2014) The influence of weather on health-related help-seeking behavior of senior citizens in Hong Kong. Int J Biometeorol. doi:10.1007/s00484-014-0831-7

    Google Scholar 

  36. World Health Organization (1978) International statistical classification of diseases and related health problems, ninth revision. WHO, Geneva

  37. World Health Organization (2007) Improving public health responses to extreme weather / heat-waves - EuroHEAT.

  38. World Meteorological Organization, World Health Organization (2015) Heatwaves and health: guidance on warning system development. WMO-No. 1142.

  39. Yaglou CP, Minard D (1956) Prevention of heat casualties at Marine Corps training centers. Harvard School of Public Health. Boston, MA.

  40. Yaglou CP, Minard D (1957) Control of heat casualties at military training centers. Am Med Assoc Arch Ind Health 16:302–316

    CAS  Google Scholar 

  41. Yi W, Chan APC (2014a) Optimal work pattern for construction workers in hot weather: a case study in Hong Kong. J Comput Civ Eng

  42. Yi W, Chan APC (2014b) Effects of temperature on mortality in Hong Kong: a time series analysis. Int J Biometeorol. doi:10.1007/s00484-014-0895-4

    Google Scholar 

  43. Yip KM, Leung YK, Yeung KH (2007) Long-term trend in thermal index and its impact on mortality. Hong Kong International Conference on Climate Change, Hong Kong, China, 29–31 May 2007

  44. Zander KK, Botzen WJW, Oppermann E, Kjellstrom T (2015) Heat stress causes substantial labour productivity loss in Australia. Nat Clim Chang 5:647–652

    Article  Google Scholar 

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The authors would like to thank the Hospital Authority for providing the data sets for this study. The authors are also thankful to colleagues of the Hong Kong Observatory, Dr. C.M. Cheng, Mr. K.C. Tsui, Mr. L.S. Lee, and Dr. Y.F. Lee, for their useful inputs and valuable comments on the manuscript.

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Correspondence to Y. H. Chan.

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Lee, K.L., Chan, Y.H., Lee, T.C. et al. The development of the Hong Kong Heat Index for enhancing the heat stress information service of the Hong Kong Observatory. Int J Biometeorol 60, 1029–1039 (2016).

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  • Heat stress
  • Heat index
  • Hot
  • Hospitalization
  • Wet bulb globe temperature