WES WEEK TEN: 12-16 November 2001

• Water well owners polled -- The results were recently released of a survey conducted by the National Ground Water Association (NGWA) of water well owners.  Roughly three-quarters of the respondents indicated that they preferred their water source and deemed the source relatively safe. [ENN]
• No-wake zones may aid in water quality of lakes -- A Penn State University researcher reported that instituting a no-wake zone in shallow portions of lakes may be better than speed limits on motorized boats since the turbulence from the wakes and the prop wash stir the bottom sediments, thereby reducing the water quality in the lake. [EurekAlert!] 
• Improved methods for cleaning up underground gasoline spills studied -- Virginia Tech researchers are studying bioremediation techniques that involve various microbes in an attempt to improve the process of cleaning up gasoline plumes that emanate from leaks in underground storage tanks. Various volatiles in the gasoline are known carcinogens. [EurekAlert!]
• More effective fertilizer applications could reduce pollution of river shed -- A scientist with the University of Illinois has shown through a computer model that more efficient means of applying nitrogen fertilizer to Midwest cropland could reduce the nitrate flux into the Mississippi River and the Gulf of Mexico, yet not reducing crop yields. He found that with a 12 percent reduction in the amount of nitrogen fertilizer applied a 33 percent reduction in the nitrates could be realized.  [EurekAlert!] 
• A large sediment role for small rivers -- Geologists at Ohio State University report that small streams from mountainous terrain can transport as much sediments to the ocean as large rivers such as the Amazon or Nile.  Their research involved mountain streams on Taiwan and New Zealand.  [Ohio State University]
• A self-cleaning Hudson River -- A team of scientists from Rutgers University and other universities reported that the water quality in the lower Hudson River estuary has improved to levels of approximately 30 years ago.  Their area of study extended approximately 40 miles upstream from New York Harbor.  They suggest that in this portion of the estuary, the natural actions of tides, storms and runoff from precipitation and snowmelt have apparently diluted and flushed many of the dangerous pollutants out to sea.  [EurekAlert!]
• A large ancient river in South Florida -- Scientists from the US Geological Survey report that sand samples found along the Caloosahatchee River in Florida indicate the existence of large sand dunes and a structure of a river delta rivaling that of the present-day deltas at the mouth of the Mississippi River.  These deposits suggest the possible existence of an ancient large river.  [EurekAlert!]
• A somber anniversary remembered  -- Saturday was the 26th anniversary of the sinking of the Great Lakes ore carrier, Edmund Fitzgerald, during a powerful storm on Lake Superior. Last year the National Weather Service Forecast Office at Marquette, MI created a web page commemorating the sinking and describing the advances in marine weather forecasting over the last quarter century.
• Earth diary - A summary of the week's major environmental events on Planet Earth. [CNN]

Concept of the Week: Water in Microclimates

Water is an important component of the planetary-scale climate system, playing a key role in the global radiation balance (e.g., the greenhouse effect) and large-scale transport of heat (e.g., latent heat transfer). The global climate system exhibits considerable spatial variability so that Earth is a mosaic of numerous climate types and water is often an important factor in distinguishing among individual climates. Hence, for example, the climate of a desert differs from that of a rainforest primarily because of differences in precipitation and potential evaporation rate.

Climate (average atmospheric conditions) also varies on smaller spatial scales. Here, we consider examples of how the local water and heat energy budget vary on the scale of microclimates, having horizontal dimensions from less than 1 m to 100 m (3.3 ft to 330 ft) and vertical dimension from Earth’s surface to an altitude of 100 m (330 ft).

All other factors being equal, afternoon air temperatures tend to be lower over an irrigated farm field than over a non-irrigated field. Where soils are wet, more of the available heat is used to evaporate water (latent heating) leaving less to raise the temperature of the soil surface and overlying air (sensible heating). In the Northern Hemisphere, snow tends to persist longer and the growing season is shorter on the shaded north- and east-facing hill slopes (facing away from the sun) than on south- and west-facing slopes (facing the sun). In portions of the Rocky Mountains, the sunnier, drier, and warmer south-facing slopes are sparsely vegetated by grasses, ponderosa pine, and juniper. Meanwhile, dense stands of fir and spruce grow on the shaded, moist, and cooler north-facing slopes.

Trees, sand dunes, buildings and other obstacles slow the wind and reduce the wind’s ability to transport material (including soil particles) in suspension. Farmers take advantage of this effect by constructing shelterbelts (or "windbreaks") that reduce wind erosion of soil and modify the microclimate. A shelterbelt may consist of a fence or multiple rows of trees or bushes planted upwind of an agricultural field—usually perpendicular to the prevailing wind direction. In the winter, snow-bearing horizontal winds slow as they encounter a shelterbelt. The wind’s ability to transport snow diminishes and snow accumulates on the field immediately downwind of the shelterbelt. The air spaces within a snow cover make it a relatively poor conductor of heat so that the snow cover protects the underlying soil from deep penetration of subfreezing temperatures. In areas where winter wheat is grown, the snow cover protects the dormant plants from potentially damaging fluctuations in soil temperature. Snow trapped by shelterbelts also increases the local supply of soil moisture that becomes available during the spring thaw. Furthermore, slowing the wind reduces the evaporation of soil moisture. Significant increases in crop yields can be attributed to the microclimatic effects of shelterbelts.

Climatic contrasts are also evident between forested and non-forested areas. Wind speed diminishes considerably within a forest—as much as 60% to 80% at a distance of only 30 m (100 ft) into a deciduous forest. Weaker winds coupled with reduced solar radiation reaching the forest floor (due to the forest canopy) decreases the amount of evaporation from the forest floor. But the relatively high rate of transpiration by forest vegetation more than compensates for the reduction in evaporation from the forest floor. Overall, the air in a forest tends to be somewhat more humid than the air over a nearby non-forested area. Even tall field crops such as corn have a similar effect on the microclimate.

Concept of the Week: Questions

1. In the Northern Hemisphere, snow is likely to persist longer on the shaded [(north-) (south-)] facing slope of a hill.
2. The relatively high humidity in forested areas is primarily the result of relatively high [(precipitation) (evaporation) (transpiration)] occurring in forested areas.

• 12 November 1956...(date approximate) The crew on the icebreaker U.S.S. Glacier saw what may have been the world's largest iceberg. Seen about 150 miles west of Antarctica's Scott Island, the iceberg was about 60 miles wide by 208 miles long, or roughly the size of Maryland. (Accord Weather Calendar)
• 12 November 1968...New England was battered by the third severe coastal storm in only 5 days. An intense low crossed Long Island and produced wind gusts to 100 mph at Block Island, RI. Tides ran 5 to 10 feet above normal in some places with severe coastal flooding and damage. Rockland, ME recorded a wind gust of 86 mph. Winds reached 90 mph in Massachusetts. Up to 10 inches of snow fell at some of the higher elevations, bringing the totals for the three storms as high as 60 inches. (David Ludlum) (Intellicast)
• 12 November 1974...A great Alaska storm in the Bering Sea caused the worst coastal flooding of memory at Nome, AK with a tide of 13.2 feet. The flooding caused 12 million dollars damage, however no lives were lost. (David Ludlum)
• 12 November 1980...A fringe rain band from Hurricane Jeannie in the Gulf of Mexico let loose a deluge of 23.38 inches of rain in 24 hours at Key West, FL, an all-time 24 hour record. (Intellicast)
• 13 November 1946...General Electric scientists produced snow in the Massachusetts Berkshires in the first modern day cloud seeding experiment. (The Weather Channel)
• 13 November 1998...The youngest son of former Canadian Prime Minister Pierre Trudeau and two companions were swept into Kokanee Lake in British Columbia's Kokanee Glacier National Park by an avalanche while on a backcountry ski trip. The companions swam to shore, but the young Trudeau drowned. (Accord Weather Calendar)
• 14-18 November 1979...Approximately 40 inches of rain were measured over northeast Hawaii, with much higher amounts likely in mountainous areas not monitored by rain gauges. The Waipio Valley was hit hard, with more than 90 percent of the valley's farmland covered by flood debris. The new 6.9 million-dollar road to Waipio Lookout that had just been dedicated was severely damaged. (Accord Weather Calendar)
• 14-21 November 1991...Tropical Cyclone Tia spend most of its life near the Solomon Islands and Vanuatu. However, it completely destroyed 90 percent of all dwellings on Tikopia Island. The remaining 10 percent of the buildings had collapsed walls or roofs that had been blown off. (Accord Weather Calendar)
• 15 November 1900...A record lake-effect snowstorm at Watertown, NY produced 45 inches in 24 hours. The storm total was 49 inches. (14th-15th) (David Ludlum) (The Weather Channel)
• 18 November 1421...Wind-driven waves from an intense storm breached Dutch dikes, sweeping away 72 villages. At least 10,000 people died in the "St. Elizabeth's" flood. (Accord Weather Calendar)
• 18 November 1873...A severe storm raged from Georgia to Nova Scotia causing great losses to fishing fleets along the coast. In Maine, the barometric pressure reached 28.49 inches at Portland. (David Ludlum)
• 18 November 1921...A storm that produced 54 inches of snow and sleet blocked the Columbia River Highway in The Dalles, OR. Railroads were stopped for days in both Washington and Oregon. (Intellicast)

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Prepared by AMS WES Central Staff and Edward J. Hopkins, Ph.D., email hopkins@meteor.wisc.edu
© Copyright, 2001, The American Meteorological Society.