Weekly Water News

DATASTREME WES WEEK TWO: 31 January-4 February 2005


Water in the News


REPORTS FROM THE FIELD--

Faye McCollum, LIT Leader from Columbus, GA, reported that last weekend's ice storm across the Southeast caused power outages as far south as Columbus. While air temperatures hovered in the low 30s, freezing rain and ice pellets fell. However, she reported no snow. Debris from the tree limbs downed in the ice storm remained in the neighbors' yards. While life was returning to normal on Monday, she was still experiencing some brief power outages on Tuesday.

Carol Hildreth, LIT leader from Mechanicville, NY, reported seeing a "beautifully colored" sun dog last week. Sun dogs, or parhelia, are optical phenomena that appear on either side of the sun at an angular departure of approximately 22 degrees (an angular distance roughly equivalent to one hand-span on an outstretched arm from the sun). These optical phenomena are caused by the bending of the rays of sunlight (refraction) by airborne ice crystals. She noted that she only saw one and not a possible second sun dog. Carol also reported on a thin band of fog one morning last week that was approximately 20 feet above a field, several meters thick and about 300 feet in length. Finally, she sent pictures of hoarfrost (feathered white ice crystals formed on trees) on a weekend trip to Vermont.


Concept of the Week: Water Chill

The epic movie Titanic dramatically portrayed how immersion in cold water can be deadly. After abandoning ship, passengers and crew who were floating in relatively calm seas perished within a short time. Residents of cold climates are warned of the dangers posed by a combination of low air temperature and strong winds (the wind-chill). Because of the special thermal properties of water, immersion in cold water can be even more hazardous. A boating accident or a plunge through thin ice on a lake can have deadly consequences.

One of the principal hazards of cold water immersion is a lowering of body temperature due to excess heat loss. (Perhaps half of all drowning victims actually die from this effect of cold water rather than water-filled lungs.) Heat is energy that is transferred between two objects at different temperatures, always flowing from the warmer to the colder object. The human body can regulate its core temperature so that it normally varies by no more than about 2 Celsius degrees (3.6 Fahrenheit degrees) above or below 37 °C (98.6 °F). Hence, heat usually flows from the human body to its cooler surroundings. Core temperature refers to the temperature of vital organs such as the heart, lungs, and kidneys.

When immersed in cold water, a body may lose heat at such a high rate that thermoregulatory processes cannot prevent a steady drop in core temperature and the victim may exhibit symptoms of hypothermia. These symptoms set in when a person's core temperature falls below 36 °C (96.8 °F). Shivering (a natural thermoregulatory process) becomes violent and uncontrollable and the victim has difficulty speaking and becomes lethargic. If the core temperature drops below 32 °C (90 °F), shivering ceases, muscles become rigid, and coordination deteriorates. At a core temperature of 30 °C (86 °F), a person may drift into unconsciousness and death may ensue at a core temperature below 24 °C (75 °F).

A person runs a greater risk of developing hypothermia when immersed in water than air at the same temperature. Water conducts heat at a rate that is more than 20 times greater than still air and water's specific heat is almost 6 times that of dry air. Whereas the risk of hypothermia due to low air temperature primarily occurs in winter, cold water immersion is possible anytime of year in many locations. Ocean or lake temperatures may remain relatively low throughout the summer months because of water's relatively great thermal inertia.

For more information on hypothermia, including expected survival time for various water temperatures, got to: http://www.seagrant.umn.edu/tourism/hypothermia.html.

Concept of the Week: Questions

  1. Water is a [(much better)(poorer)] conductor of heat than still air.
  2. Hypothermia is a potentially lethal [(rise)(fall)] in the temperature of the human body's vital organs.


Historical Events


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Prepared by DS WES Central Staff and Edward J. Hopkins, Ph.D.,
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hopkins@meteor.wisc.edu
© Copyright, 2005, The American Meteorological Society.