DATASTREME WES WEEK FOUR: 16-20 February 2004

• Coral reefs threatened by climatic change and pollution -- In a report authored by scientists at the National Center for Atmospheric Research, the Kansas Geological Survey and Dauphin Island Sea Lab, a warning has been issued that warns that changes in the surface temperature and chemistry of the oceans will continue to damage coral reefs, biologically vital and economically important ecosystems. [EurekAlert!] Harbor Branch scientists suggest that pollution from such sources as sewage and agricultural runoff, is the main cause of the coral-smothering spread of seaweed on many reefs. [EurekAlert!]
• Lakeshore property values increase with restrictions -- An interdisciplinary group of researchers at the University of Wisconsin-Madison reported that property values increased along the shorelines of lakes in northern Wisconsin when action was taken to protect the quality of these lakes. [EurekAlert!]
• Former foes working to manage Colorado water shortage-- Faced with a continuing drought, the recent annual meeting of the Colorado Water Congress featured a gathering of various groups from across the state that had fought for the scarce water but now are in need to find ways at better water management. [US Water News]
• Measuring snowpack in Idaho -- The snow survey program in Idaho is described, along with its history. [Ag Weekly Online]
• Species protection programs could be threatened -- A recent ruling by a federal judge in California could spell major problems for programs designed to protect endangered species. The judge ruled that millions of dollars can be awarded to farmers who lost water because of an effort a decade ago designed to save two rare fish species. [ENN]
• Camera could aid fishing industry -- A Danish inventor recently demonstrated a new camera that could take digital pictures of the catch of fish caught in nets and quickly identify individual species, thereby permitting the culling out of unwanted fish. [ENN]
• The "iron fertilization" experiment still unproven -- A Duke University scientist reported that the decade-long small scale "iron fertilization" experiment whereby iron particles were broadcast across ocean waters in an attempt to promote increased photosynthesis by marine phytoplankton have not demonstratively produced the significant reduction in the absorption of atmospheric carbon dioxide needed to alleviate global warming. [EurekAlert!]
• More tropical rains foreseen for a warmer world -- Scientists at NASA's Goddard Space Flight Center predict that if tropical oceans continue to warm following an observed 20-year trend, then warm rains in the tropics would likely become more frequent, as patterns of evaporation and precipitation may accelerate in some areas due to increased temperatures. [EurekAlert!]
• A new stage reached by the Hudson River Estuary -- Based on analysis of sediment accumulation, geologists at Lamont-Doherty Earth Observatory and Queens College have found that the stretch of the Hudson River called the Hudson River Estuary has reached what they consider as middle age. [The Earth Institute at Columbia University]
• Damming a river could have disastrous consequences -- Environmentalists have warned that a proposed dam on the Okavango River would cause the death of the extraordinary Okavango Delta in Botswana of southern Africa. [ENN]
• Tracking atmospheric carbon to beneath the ocean floor -- An earth science professor at Rice University recently reported on his analysis of clathrate hydrates located just beneath the ocean floor. He suggests that these ice-like substances formed from water, methane and other gases by various biological and geological processes represent an enormous pool of carbon in the form of methane. [Rice University]
• Global and US Hazards/Climate Extremes -- A review and analysis of the global impacts of various weather-related events, including drought, floods and storms during the current month. [NCDC]
• Global Water News Watch -- Other water news sources can be obtained through the SAHRA Project at the University of Arizona [SAHRA Project]
• Earthweek --Diary of the Planet [earthweek.com] Requires Adobe Acrobat Reader.

Concept of the Week: Controlling Indoor Humidity

In public buildings as well as individual homes, it is sometimes desirable to alter extremes of relative humidity so that living spaces are more comfortable. For human comfort, optimum relative humidity is between about 30% and 50%. When indoor air is exceptionally dry, a humidifier may be used to add water vapor to the air, but when indoor air is excessively muggy, a dehumidifier may be used to remove water vapor from the air.

As cold, dry winter air is drawn indoors and heated by a furnace, its relative humidity declines--sometimes to uncomfortably low levels. Suppose, for example, that outdoor air has a temperature of -20 ºC (-5 ºF) and relative humidity of 50%. If that air were brought indoors and heated to 21 ºC (70 ºF), its relative humidity drops to about 2% -- well below the optimal winter indoor relative humidity of 30% to 50%. At such very low relative humidity values, people often feel discomfort caused by dry skin and irritation of the mucus membranes in their nose and throat. Also, wood furniture dries out and may crack and become unjointed. Discharge of static electricity (e.g., after walking across a carpet and touching a metal doorknob) can be a nuisance in dry rooms.

One remedy for excessively low indoor relative humidity is a device known as a humidifier. A humidifier elevates the relative humidity of indoor air to more comfortable levels by evaporating water into the air (increasing the vapor pressure). A common humidifier design consists of a wheel that continually rotates a porous belt (or pads) into and out of a reservoir of water. A fan blows air through the wetted belt, water evaporates into the air stream, and the more humid air circulates through the dwelling.

On the other hand, a dehumidifier may be desirable during warm muggy summer days. In addition to discomfort caused by reduced evaporative cooling, high values of indoor humidity can increase the incidence of mold and mites. A dehumidifier lowers the relative humidity of indoor air to more comfortable levels by inducing condensation of water vapor (decreasing the vapor pressure). In a standard dehumidifier, a fan draws humid air past a cold refrigerated coil. Air in contact with the coil is chilled to saturation, water vapor condenses on the coils and liquid water drips from the coils into a collection reservoir or through a hose into a drain. Most dehumidifiers function best when the air temperature is at or above 18 ºC (65 ºF).

Click on forecast map for locations across the country where today's indoor relative humidity is expected to be too high or too low in the absence of any controls on indoor humidity. For an interactive applet (from the University of Wisconsin-Madison) that explores the relationships between temperature, dewpoint, and relative humidity, go to http://profhorn.meteor.wisc.edu/wxwise/museum/a7/a7exercise1.html. Follow instructions and note how the indoor relative humidity changes with changes in outdoor conditions.

Concept of the Week: Questions

1. A humidifier elevates the relative humidity by causing [(evaporation)(condensation)].
2. A dehumidifier reduces the relative humidity by causing [(evaporation)(condensation)].

• 16 February 1966...Heavy rain fell in Whenuapai, New Zealand, with 4.2 inches of rain falling in one hour, the record for that time in New Zealand. (The Weather Doctor)
• 19 February 1972...A vicious coastal storm dumped 10 to 20 inches of snow over interior sections of the mid-Atlantic and Northeast states and caused some of the worst coastal damage this century in New England. Twenty-three inches of snow fell at McHenry, MD, 23 inches piled up at Williamsport, PA, and Syracuse, NY recorded 20 inches. Twenty-foot drifts were reported in northeastern Pennsylvania. Storm surges up to 4.5 feet and winds gusting over 80 mph along coastal Rhode Island, Massachusetts, New Hampshire, and Maine resulted in extensive property damage and tremendous beach erosion. Twenty-seven houses were destroyed and 3000 damaged in Massachusetts alone. (Intellicast)
• 20 February 1805...The Potomac River was opened after being closed by ice for a period of two months. (Sandra and TI Richard Sanders - 1987)
• 20 February 1997...A vast mudslide swept off an Andean mountainside onto two remote villages in southeastern Peru burying up to 300 people. Inhabitants had been evacuated after weekend flooding, but their refuge above the village put them in the path of the mudslide. (The Weather Doctor)
• 21 February 1992...Today marked the 16^th consecutive day that Sacramento, CA recorded measurable rain, breaking the old record of 15 consecutive days set back in February 1936 and again in November 1970. Total rainfall over the 16-day period was 6.41 inches. (Intellicast)
• 22 February 1986...A twelve-day siege of heavy rain and snow, which produced widespread flooding and mudslides across northern and central California, finally came to an end. The storm caused more than 400 million dollars property damage. Bucks Lake, located in the Sierra Nevada Range, received 49.6 inches of rain during the twelve-day period. (Storm Data)
• 22-26 February 1995...Cyclone Bobby slammed into the Western Australia coast causing widespread flooding. Some areas reported up to 12 inches of rain from the storm. (The Weather Doctor)

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Prepared by AMS WES Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2004, The American Meteorological Society.