Bioclimates of heat and cold stress in New Zealand | The Meteorological Society of New Zealand

Bioclimates of heat and cold stress in New Zealand

C. de Freitas

Climatic variables, level of activity and clothing are combined to produce easy to interpret indices of human thermal climates of the four main urban areas of New Zealand: Auckland, Wellington, Christchurch and Dunedin. Two approaches called HEBIDEX and CLODEX each produce an index of climate in fundamentally different ways. However, both schemes are similar in that they deal with the real processes of heat exchange between the person and the environment. HEBIDEX is expressed as the net body-atmosphere heat imbalance in either hot or cold environments of people wearing specified types of clothing. The index values can be readily interpreted in straight forward descriptive terms using a standard thermal sensation scale. Human climate is expressed by CLODEX as the actual clothing required in cool or cold conditions to keep an individual comfortable. Indices are presented for two reference states which give the user an impression of the effect of activity level on interpretations of climate. The results show that, for an inactive person, the climates of the four urban areas are characterised generally by cool and sometimes cold daytime conditions. Yet, conditions of severe cold stress are rare, even during mid-winter at night. The climate during the summer months is generally moderate, tending towards the cool side of neutral.

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