1. WEATHER, CLIMATE
AND
HUMAN COMFORT

2. HUMAN ENERGY BALANCE Q S M M = Metabolism (Heat - Work) IR
Q = Shortwave solar IR
IR = Infrared (in and out) M
M = Metabolism
(Heat - Work) S
S = Storage
SEN
SEN = Sensible (in and out) E
E = Evaporation (out only)
Processes that convert food to energy to sustain body’s functioning

3. HUMAN ENERGY BALANCE Q S Goal: Keep “S” close to zero (“homeostasis”)IR
SEN E S
Goal: Keep “S”
close to zero
(“homeostasis”)
M + Q ± IR ± SEN – E= ±S

4. Homeostasis: mechanisms that attempt to maintain a relatively
constant core body temperature (or at least a narrow range)
(i.e., S = 0)
Average core (rectal) temperature = 98.6°F (37°C)
Low core temperatures = hypothermia (<95°F or so)
High core temperatures = hyperthermia (>104°F or so)

5. COLD CONDITIONS – SEN insulating layer of air skin
Rapid sensible heat loss can result
– SEN
insulating layer of air
skin
Wind reduces insulating layer

6. HYPOTHERMIA Low core temperature from: exposure to a cold environment
drug and alcohol use
improperly functioning thyroid
Body’s response:
muscle shivering to generate heat
thyroid releases hormones to increase metabolism
vasoconstriction: blood vessels constrict flow to skin, keeping heat closer to body’s core

7. Vasoconstriction
Reduces sensible heat loss by keeping heat closer to body core

8. Progression to Frostbite

9. (OLD) WIND CHILL INDEX Combination of air temperature and wind speed
Assumes walking speed (3 kts)
Person not wearing clothing

11. HYPOTHERMIA Core temperature < 95°F (35°C)
Wet clothing raises sensible heat loss
Symptoms
Exhaustion
Lack of coordination
Shallow breathing
Weak pulse
Shivering (if not too far along)
Loss of reasoning power, memory loss
Stupor
Death
Often occurs above freezing!

12. HOT CONDITIONS Tw = 70˚F Tskin = 88˚F Strong Evaporation Rapid Cooling

13. HOT CONDITIONS Tw = 86˚F Tskin = 88˚F Reduced Evaporation
Slight Cooling
Tw = 86˚F
skin
Tskin = 88˚F

14. RAPID RISE IN BODY CORE TEMPERATURE!
HOT CONDITIONS
No evaporation—
body gains heat
from atmosphere
Tw = 90˚F
skin
Tskin = 88˚F
RAPID RISE IN BODY CORE TEMPERATURE!
(Hyperthermia)

15. HYPERTHERMIA High core temperature from:
exposure to a hot environment (dry or humid)
exercise
digestion
fever
Body’s response:
sweating (evaporative cooling)
vasodilatation: blood vessels widen, increasing flow to skin and away from core where it can radiate away

16. Vasodilatation

17. HEALTH AND EXCESSIVE HEAT
Heat Cramps
Exercise in heat
Cramping of specific muscles
Fluid loss or electrolyte imbalance from excessive sweating and salt loss
Heat Exhaustion
Dizziness, weakness, fatigue
Slight elevation of body core temperature
Often related to fluid loss to replace perspiration
Heat Stroke
Body core temperature exceeds 105˚F
Sweating response shuts down, evap.cooling stops
Person becomes delirious or comatose
15% of those affected die

18. APPARENT TEMPERATURE (“Heat Index”)
Temperature a person “feels”
Summer equivalent of wind chill index
Depends on temperature and humidity
Some versions include wind speed

19. Apparent Temperature (Heat Index)
Page: 108
FIGURE 4.21 Air temperature (°F) and relative humidity are combined to determine an apparent temperature or heat index (HI). An air temperature of 96°F with a relative humidity of 55 percent produces an apparent temperature (HI) of 112°F.

20. Chicago Heat Wave, 1995

21. Other Topics Related to Human Biometeorology
Air pollution impacts on human health
Acclimatization and adaptation to weather changes
Disease transmission and weather (e.g., influenza)
Vector-borne diseases (dengue fever, malaria, etc.)
Climate and occupational health and productivity
Exercise physiology
Tourism