The Hong Kong Polytechnic University
Department of Applied Physics
Weather and Our Feelings
(Author: Ng Wai Fong)
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
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Temperature and thermal feelings
• What does the temperature in weather report
refer to?
– Temperature of Air
• What is cold/hot?
– The feelings of human on temperature
• 15℃ = Cold? 35℃ = Hot?
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
Related Weather Warnings from
Hong Kong Observatory
Cold Weather Warning
– Winter Only
Very Hot Weather Warning
– Summer Only
Is it enough?
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
Weather and Our Feelings
• Factors that influence us on the thermal feelings:
–
–
–
–
Temperature
Wind Speed
Relative humidity
Radiation of the Sun
• Example:
– A hot weather with high relative humidity hinder heat loss
by the evaporation of sweat, low wind speed will also
lower heat loss from human body, thus increasing the level
of discomfort.
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
Heatstroke
• Under very hot weather, who are having a
greater risk of a heatstroke?
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
Weather and Our Feelings
Scientists make use of weather data to estimate human feelings
•Thermal comfort (熱舒適度)
– The satisfactory level of human towards the coldness/hotness of
environment
• Eg. Hot, warm, slight warm, neither cold nor hot, just right, slight cool,
cool, cold
• The condition of the heat exchange between human body and
environment
– Factors
•
•
•
•
•
•
Temperature
Humidity
Air Current
Hot Radiation
Metabolism
Clothing
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
Weather and Our Feelings
Ways to express the comfort level due to heat:
• Net Effective Temperature (NET)
• Heat Index (HI) – Summer Only
• Humidex (HMI) – Summer Only
• Apparent Temperature (AT)
• Wind Chill Index (WCI) – Winter
• Wet Bulb Globe Temperature Index (WBGT)
2008 Summer Olympics Equestrian Events in Hong Kong
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
(Activity 1) Calculations:
Apparent Temperature AT
• AT = Ta + 0.33×e − 0.70×ws − 4.00
where, e = rh / 100 × 6.105 × exp ( 17.27 × Ta / ( 237.7 + Ta ) )
Air Temperature, Ta (°C)
25
30
35
38
Relative Humidity,rh (%)
50
50
50
50
Wind Speed, ws (km/h)
5
5
5
5
Apparent Temperature,
AT (°C)
22.71
29.48
36.74
41.39
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
(Activity 1) Calculations:
Apparent Temperature AT
• AT = Ta + 0.33×e − 0.70×ws − 4.00
where, e = rh / 100 × 6.105 × exp ( 17.27 × Ta / ( 237.7 + Ta ) )
Air Temperature, Ta (°C)
30
30
30
30
Relative Humidity, rh (%) 20
40
60
80
Wind Speed, ws (km/h)
5
5
5
5
Apparent Temperature,
AT (°C)
25.29
28.08
30.87
33.66
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
(Activity 1) Calculations:
Apparent Temperature AT
• AT = Ta + 0.33×e − 0.70×ws − 4.00
where, e = rh / 100 × 6.105 × exp ( 17.27 × Ta / ( 237.7 + Ta ) )
Air Temperature, Ta (°C)
35
35
35
35
Relative Humidity, rh (%) 50
50
50
50
Wind Speed, ws (km/h)
0
5
10
20
Apparent Temperature,
AT (°C)
40.24
36.74
33.24
26.24
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
(Activity 2) Scientific Experiment:
Estimating Human’s Feelings on Weather
• Refer to the worksheet
(Scientific Experiment: Estimating Human’s
Feelings on Weather by Ng Wai Fong)
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.
(Activity 3) Investigation on the
Wet Bulb Globe Temperature
Video:
http://www.weather.gov.hk/wservice/cstdi/cstdic.htm
Discussions:
•What is the use of Wet Bulb Globe Temperature (WBGT)?
•Why Heat Stress Index is better than other weather information?
•Should Heat Stress Index be used and disseminated?
•Students can discuss the issues about disseminating Heat Stress Index to the public
through a role play with different characters:
– Representative of the industrial and commercial sector
– Representative of the transport services
– Director of the Hong Kong Observatory
– School Principal
This work by Ng Wai Fong of the Department of Applied Physics, The Hong Kong Polytechnic University, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Hong Kong License, based on the information provided by
Creative Common. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/hk/deed.zh_HK.