DATASTREME WES WEEK TEN: 4-8 April 2005

• Need for global tsunami warning system voiced -- The Director of the National Weather Service, David L. Johnson, called for an improved global tsunami warning system following last week's major earthquake off the Indonesian coast, which did not produce a significant tsunami as originally feared. [NOAA News]
• April is Tsunami Awareness Month in Hawaii -- The National Weather Service along with state civil defense agencies in Hawaii conducted a statewide tsunami warning and response exercise last Friday, kicking off Hawaii's Tsunami Awareness Month activities. The Aloha State has experienced several deadly tsunamis in the last 60 years. [NOAA News]
• Recent storms help relieve the Western drought- Several storms that originated over the Pacific brought welcome precipitation to the drought-stricken West last week.
• A snowstorm that brought snow to the Cascades in Washington State not only helped build the depleted snowpack, but also give life to the ski areas. [USA Today]
• Recent snows have brought the snow pack in the high Sierras near Lake Tahoe to levels that are between 125 to 140 percent of normal. [USA Today]
• A series of recent heavy snowstorms across the southern Rockies has caused water resource officials to release water from the reservoir serving Santa Fe, NM to make room for the anticipated snowmelt. [USA Today]
• Helping to restore Chesapeake Bay oysters -- Several agencies within NOAA have been collaborating with other agencies in the federal and state governments along with environmental organizations and concerned citizens to clean and restore the waters of Chesapeake Bay, together with introducing resistant species so as to return the nation's largest estuary to a major oyster habitat. [NOAA Magazine]
• Population density increases along the nation's coastal areas -- A recently released NOAA report entitled "Population Trends Along the Coastal United States: 1980-2008" documents the finding that as of 2003, more than half the nation's population lived within a coastal area along the Atlantic and Pacific Oceans, the Gulf of Mexico and Great Lakes that comprises only 17 percent of the land area. This report also forecasts that the population densities along the coasts should continue to increase in the next five years, along with additional coastal development that could make these coastal areas more vulnerable to pollution and other coastal hazards. [NOAA Magazine]
• High levels of toxins found in Washington State fish -- The Department of Ecology in Washington State recently reported that freshwater fish taken from the Spokane River had high levels of polybrominated diphenyl ethers (PBDE), which are flame retardants concerned to be toxic. [ENN]
• Indian Ocean observing network is developed -- A large observing network, sponsored by several nations and administered by the international Indian Ocean Panel, is being developed to monitor the ocean temperatures and currents in the Indian Ocean in order to understand how that ocean influences the conditions that produce episodes of rain and drought across those areas surrounding the Indian Ocean that are home to nearly two-thirds of the planet's population. [EurekAlert!]
• Oceans respond to climate changes in both hemispheres -- A team of researchers from the Universitat Autònoma de Barcelona and Cardiff University have demonstrated that climate changes in both the northern and southern hemispheres are linked because the ocean circulation in the southern hemisphere has responded to sudden changes in the circulation in the northern hemisphere. [EurekAlert!]
• Earth and its residents in peril --
• In a recently released report called the "Millennium Ecosystem Assessment", a group of scientific experts from 95 countries warn that fresh water along with other resources have declined around the world in the past 50 years and could threaten billions of people within the near future unless improved ecosystem management is not adopted. One of the report's findings was that the demand for water for both industry and domestic purposes has doubled since 1960. [EurekAlert!]
• Researchers from Columbia University, the Norwegian Geotechnical Institution and the World Bank released the first volume of "Natural Disaster Hotspots: A Global Risk Analysis" that presents a global assessment of the disaster risks associated with several major national hazards, including drought, floods, cyclones (especially tropical cyclones such as hurricanes), earthquakes, volcanoes and landslides. The report indicates that more than half the world's population currently lives in areas where at least one of these hazards could significantly impact them. [Earth Institute at Columbia University]
• Termination of ice ages controlled by changes in orbital tilt -- Using a model based upon the rate at which sediment deposits upon the ocean floor, researchers at the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology recently reported that periodic changes in the tilt of the earth's spin axis on the order of 100,000 years appear to signal changes in the cycles in glaciation, primarily in the rapid termination of these glacial events. [EurekAlert!]
• Monitoring landslides from space--The European Space Agency has funded a Service for Landslide Monitoring (SLAM) that uses satellite imagery from the agency's ERS satellites to monitor the hydrogeology of the watersheds in the Umbria and Tuscany regions of Italy that are susceptible to landslides [ESA]
• 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.

• 4 April 1933...Pigeon River Bridge, MN reported 28 in. of snow, which established the state 24-hr snowfall record. (4^th-5^th) (The Weather Channel)
• 4 April 1973...Sandia Crest, NM reported a snow depth of 95 in., a record for the state of New Mexico. (The Weather Channel)
• 4 April 1987...New England was in the middle of its second heavy rainstorm in 5 days. This was the same storm that produced record snows in the Appalachians. This storm dumped 4 to 7 in. of rain over the area and this, combined with snowmelt and rivers already at bankfull, produced record flooding, especially in Maine, where 2300 homes were flooded with 215 totally destroyed. Record water levels were reached at many dams. Damage in the state alone reached $100 million. (The National Weather Summary) (Storm Data) (Intellicast)
• 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 from the 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 in. 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 in. Eighty-two people were killed and 100,000 were made homeless. Damage was greater than 150 million US dollars. (Accord's Weather Guide Calendar) (The Weather Doctor)
• 9 April 1977...A storm brought 15.50 in. 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 in. 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, NC. (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 were needed to clear the debris from roads. Downtown Port Clinton streets were flooded. (Accord's Weather Guide Calendar)

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