DataStreme WES Week Four: 14-18 February 2005

• Flooding rains plague the Southwest--A storm system that brought a plume of humid air northward from the tropical Pacific spread heavy rains across the typically arid sections of southern California, Arizona and New Mexico. Especially hard hit was central Arizona's Mogollon Rim north of Phoenix where some streams flooded due to the heavy rain and the snowmelt from the heavy snow cover in the mountains. Many residents were forced to evacuate. [USA Today] [CNN]
• Snowstorm was a nuisance but welcome -- The storm that dropped more than 2 feet of heavy, wet snow across northern New England at the end of last week caused travel and power disruptions, but was welcomed by ski resorts because the new snow could attract increased business on the upcoming President's Day weekend [USA Today]
• Dam failure proves deadly--Pakistani officials reported that a large dam in southwest Pakistan broke because of heavy rains late last week, resulting in the deaths of at least 54 people. More than 400 others remained missing because of the flooding that also caused much destruction of property. [USA Today]
• Snow in Iran--Record snowfall was reported across northern Iran late last week. [USA Today]
• January 2005 created water woes in the West -- Scientists at the National Climatic Data Center reported that much below average precipitation across the Pacific Northwest was responsible for worsening the drought across the region, while a series of storms produced much above average to the Southwest, were some locations received record rains leading to flooding and mudslides. [NOAA News]
• Western drought could persist -- A recently released study by the Energy and Environmental Research Center indicates that based upon analysis of lake sediments, significant drought could persist across the Plains for the next several decades. [US Water News Online]
• Recent Alaskan oil spill was big -- Alaskan state environmental officials reported last week that the fuel oil spilled into the Bering Sea from a cargo ship that ran aground in the Aleutians and split was the largest spill since the infamous 1989 Exxon Valdez disaster. [ENN]
• Middle East cooperation for river clean-up -- Local Israelis and Palestinians have agreed to cooperate and clean up the Alexander River that flows near Tel Aviv, Israel. The clean-up operation could improve the quality of the drinking water and save an endangered soft-shell turtle species. [ENN]
• College students to study melting ice shelves in Antarctica -- Undergraduate researchers from five colleges in the Northeastern States and Canada are heading to Antarctica in mid February to study the paleohistory of the Larsen Ice Shelf that has been melting and resulted in the collapse of Larsen B, a massive ice sheet. [Hamilton College]
• 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)].

• 14 February 1954...A waterspout was observed two miles east of Baranof, AK, an unusual occurrence for Alaska, particularly in winter. Just prior to the formation of the waterspout, a "terrific wind from the south out of a bay inside Warm Springs Bay" lifted water 20 feet and looked "as if it were boiling". (Accord's Weather Guide Calendar)
• 15 February 1982...An intense cyclone (low pressure system) off the Atlantic coast of Newfoundland capsized the Ocean Ranger, a drilling rig, killing 84 persons, and sank a Soviet freighter resulting in 33 more deaths. The cyclone produced 80-mph winds that whipped the water into waves fifty feet high. (David Ludlum)
• 15 February 1998...A "rogue" wave from the Pacific Ocean swept into the harbor at Port Arena, CA. This wave continued through a harbor parking lot, depositing sand, debris and logs, as well as moving thirty parked vehicles. No injuries were sustained. (Accord's Weather Guide Calendar)
• 16 February 1966...Heavy rain fell in Whenuapai, New Zealand, with 4.2 inches of rain falling in one hour, a new 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 of the 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)

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URL: DS WES:/news.html
Prepared by AMS WES Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2005, The American Meteorological Society.