DATASTREME WES WEEK TEN: 5-9 April 2004

• Heavy rains causing flooding in New Mexico -- Two days of heavy rains and mountain snows from a spring storm produced floods in southeast New Mexico near Carlsbad and icy roads near Albuquerque and Las Vegas in the north. Ironically, New Mexico had been especially hard hit by severe to extreme drought conditions for the last several years. [USA Today]
• Tsunami Awareness Month in Hawaii -- Officials with the NOAA Pacific Tsunami Warning Center and the International Tsunami Information Center recently announced that the month of April is Tsunami Awareness in the Aloha State. Their announcement commemorating the destructive tsunami on 1 April 1946 that cost 159 people their lives. Several events and programs have been scheduled during this month to help educate and inform Hawaiians of the dangers associated with tsunamis, an ocean wave that is generated by a submarine earthquake, volcano or landslide and can travel great distances. [NOAA News]
• California surfers face additional hazards-- Researchers at the University of California, Irvine recently reported on a study of surfers in California. They suggest that surfers near Los Angeles ran a greater health risks than in less urban coastal regions because of the higher coliform counts and pollutants in runoff of rainwater from the impermeable paved surfaces and roofs in urban areas. [Center for the Advancement of Health]
• US company withdraws the sale of bottled water in Britain -- The Coca-Cola Company recently announced that it was withdrawing sale of its Dasani bottled water in Britain as a precautionary measure after high levels of the chemical bromate were found in samples of the water. [US Water News Online]
• Cruise liner dumping restrictions negotiated -- The Washington State Department of Ecology has recently negotiated with cruise ship operators in an effort to reduce the amount of wastewater dumped from the large cruise liners in the state's inland marine waters. [US Water News Online]
• Alaska governor invites drilling in state waters near wildlife refuge -- Gov. Frank Murkowski announced that he plans to open lease sales in state waters offshore of the Arctic National Wildlife Refuge and the National Petroleum Reserve-Alaska. [ENN]
• Giving a pill for toxic plumes -- Geologists at the Ohio State University reported that solid potassium permanganate placed in organic material could be buried in wet soil, where the chunks slowly dissolve, releasing the potassium permanganate at a pollution site where it would reduce the pollution from industrial grade solvents. [EurekAlert!]
• A possible solution to mercury pollution developed -- Scientists at the Pacific Northwest National Laboratory of the US Department of Energy have developed a synthetic material that can remove mercury and other toxic chemicals from the waste water of coal-burning power plants. [EurekAlert!]
• State of the Planet assessed-- An international meeting of scientists at Columbia University last week examined the current condition of the planet as well as the human condition. Their goal involves "mobilizing the sciences to fight global poverty." One of the four essential determinants of human well being is water. A list of four encompassing recommendations was prepared to address the challenges faced by humans. [EurekAlert!]
• Protecting fish could be pricey -- A ruling by a federal judge at the end of last year has ordered the federal government to pay nearly $14 million dollars to 5 water districts in the San Joaquin Valley of central California as a result of reduced water deliveries when pumps on the California Aqueduct were shut down to protect threatened fish. [ENN]
• 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: 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 and ocean currents). 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 between individual climates. Hence, for example, the climate of a desert differs from that of a rainforest primarily because of differences in precipitation totals and potential evaporation rate.

Climate (long-term 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. However, 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.

• 5 April 1926...A reported 0.65 in. of rain fell in one minute at Opid's Camp, CA (Intellicast)
• 5 April 1987...After days of heavy rain that drenched eastern New York State with 5 to 8 in., a New York State Thruway bridge over Schoharie Creek collapsed just west of Amsterdam, New York. Ten people died when their vehicles plunged into the flood-swollen creek either with or shortly after the bridge collapse. (Intellicast)
• 6 April 1900...The worst flood on record in the Brazos River watershed of Texas occurred during the interval 5^th through the 8^th. An average of 17 in. of rain fell over a 7000-square mi area, while 33 in. fell on Turnersville and an estimated 30 in. at Hearme since the rain gage overflowed at 24 in. More than 30 deaths resulted from the floods. (Accord's Weather Guide Calendar)
• 6 April 1987...Rain and melting snow caused flooding from New England to Ohio. Flooding in the Merrimack Valley of Massachusetts was the worst in fifty years, causing $42 million in damage. (The National Weather Summary) (Storm Data)
• 7 April 1952...The breakup of ice along the Missouri River and its tributaries at Bismarck, ND, and above, and on the Big Sioux, created the worst flood conditions in that area in thirty years. U.S. Coast Guard personnel rendered assistance in that major disaster, evacuating stranded persons and providing other needed assistance. (US Coast Guard Historians Office)
• 8-10 April 1958...A global 48-hour precipitation record was established at Aurere, La Reunion Island , when 97.1 inches of rain from a tropical cyclone fell on the Indian Ocean island. (The Weather Doctor)
• 8-14 April 1984...Intense Tropical Cyclone Kaimsy crossed and re-crossed the northern portion of Madagascar. Winds exceeding 112 mph destroyed 80 percent of Antseranana and Mahajanga. Rainfall from this system reached 27.99 inches. Eighty-two people were killed and 100,000 were made homeless. Damage was greater than 150 million US dollars. Rainfall totals reached 27.99 inches. (Accord's Weather Guide Calendar) (The Weather Doctor)
• 9 April 1977...A storm brought 15.50 inches of rain to Jolo, WV in thirty hours. (The Weather Channel)
• 9-13 April 1991...A 3-mile long ice jam on the St. Johns River in Maine broke up, resulting in a 30-foot wall of ice. The ice crushed cars and destroyed bridges and houses. In Allagash, the sight was described as "surreal" -- "like walking on the moon." . (Accord's Weather Guide Calendar)
• 9 April 2000...A record April snowfall of 14.6 inches shut down Montreal, Quebec. Snow removal contracts had ended on 1 April. (The Weather Doctor)
• 10 April 1877...The first of two great coastal storms struck the Virginia and North Carolina coasts. The Oregon Inlet was widened by three-quarters of a mile. The "entire topography of country is materially altered", according to a description of the altering of sand dunes at Cape Hatteras. (Intellicast)
• 10 April 1996...A strong coastal storm gave New England is second heavy snowfall in only 3 days. North Foster, RI was buried under 21.5 inches of snow, while Jaffery, NH measured 21 inches. Other heavy totals included 27.4 inches on Mount Washington, NH, 20.1 inches at Ashburnham, MA, 17 inches at Windham, CT, and 12.6 inches at Brookhaven, NY. Tree damage was extensive due the heavy, wet nature of the snow. This storm took care of the remaining seasonal snowfall records as records were exceeded at the Blue Hill Observatory in Milton, MA, Worcester, MA, Concord, NH, and Bridgeport, CT. Many locations in the northeast now exceeded 120 inches for the winter season, with a few locations over 150 inches, making the winter of 1995-96 without question the snowiest winter on record for a large part of the Northeast. (Intellicast)
• 10 April 1998...Northeast winds at 40 mph on the 9^th and 10^th combined with high levels of Lake Erie produced waves to 14 feet along the lakeshore in Ottawa and Sandusky Counties in Ohio. Much damage resulted, along with the destruction of 10 houses. Bulldozers needed to clear the debris from roads. Downtown Port Clinton streets were flooded. (Accord's Weather Guide Calendar)
• 11-14 April 1984...Ice from an ice storm accumulated up to 6 inches thick on power lines in St John's, Newfoundland. Power outages left 200,000 residents of Avalon Peninsula in the dark and cold. (The Weather Doctor)
• 11 April 1987...Ten days of flooding in the northeastern U.S. finally came to an end. Damage from flooding due to rain and snowmelt ran into the billions of dollars. The collapse of the New York State Thruway Bridge over Schoharie Creek claimed ten lives. (Storm Data)

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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.