Tuesday, 31 July 2012

The American drought


Western North America Faces 21st Century 'Mega-drought'
The climate's "new normal" for most of the coming century will parallel the long-term drought that hit western North America from 2000 to 2004 - the most severe drought in 800 years - scientists report in a study published Sunday.


ENS,
30 July, 2012

"The severity and incidence of climatic extremes, including drought, have increased as a result of climate warming," the researchers said, adding that these long-term trends are consistent with a 21st century "megadrought."

Crops and forests died and river basins dried, but as bad as conditions were during the 2000-04 drought, in the future they may be seen as the good old days, a group of 10 researchers warned Sunday in the journal "Nature Geoscience."


Pinyon pine forests near Los Alamos, New Mexico, had begun to turn brown from drought stress in 2002, left. Another photo taken in 2004 from the same vantage point, right, show them grey and dead. (Photo by Craig Allen, U.S. Geological Survey)

Climate models and precipitation projections indicate this period will be closer to the "wet end" of a drier hydroclimate during the last half of the 21st century, the scientists said.

"Climatic extremes such as this will cause more large-scale droughts and forest mortality, and the ability of vegetation to sequester carbon is going to decline," said Beverly Law, a co-author of the study, professor of global change biology and terrestrial systems science at Oregon State University, and former science director of AmeriFlux, an ecosystem observation network.

The 2000-04 drought had the effect of amplifying climate change as vegetation withered and could no longer take up the greenhouse gas carbon dioxide from the atmosphere.

This drought cut carbon sequestration by an average of 51 percent in the western United States, Canada and Mexico, the scientists calculate, although some areas were hit much harder than others. As the plants died, they released more carbon dioxide into the atmosphere, with the effect of amplifying global warming.

"During this drought, carbon sequestration from this region was reduced by half," Law said. "That's a huge drop. And if global carbon emissions don't come down, the future will be even worse."

The effects are driven by human-caused increases in temperature, with associated lower soil moisture and decreased runoff in all major water basins of the western United States, researchers said in the study.


Drought has affected Colorado farm lands near Strasburg, Colorado, July 21, 2012. (Photo by Lance Cheung, USDA)

It is not clear whether or not the current drought in the West and Midwest, now being called one of the worst since the Dust Bowl, is related to these same forces, Law said. This study did not address that, and there are some climate mechanisms in western North America that affect that region more than other parts of the country.

But in the West, this multi-year drought was unlike anything seen in many centuries, based on tree ring data. The last two periods with drought events of similar severity were in the Middle Ages, from 977-981 and 1146-1151. The 2000-04 drought affected precipitation, soil moisture, river levels, crops, forests and grasslands.

Ordinarily, Law said, the land sink in North America is able to sequester the equivalent of about 30 percent of the carbon emitted into the atmosphere by the use of fossil fuels in the same region.

But based on projected changes in precipitation and drought severity, scientists said that this carbon sink, at least in western North America, could disappear by the end of the century.

"Areas that are already dry in the West are expected to get drier," Law said. "We expect more extremes. And it's these extreme periods that can really cause ecosystem damage, lead to climate-induced mortality of forests, and may cause some areas to convert from forest into shrublands or grassland."

During the 2000-04 drought, runoff in the upper Colorado River basin was cut in half. Crop productivity in much of the West fell five percent. The productivity of forests and grasslands declined, along with snowpacks.

Evapotranspiration decreased the most in evergreen needleleaf forests, about 33 percent.

Although regional precipitations patterns are difficult to forecast, the researchers said in this report that climate models are underestimating the extent and severity of drought, compared to actual observations.

They say the situation will continue to worsen, and that 80 of the 95 years from 2006 to 2100 will have precipitation levels as low as, or lower than, this "turn of the century" drought from 2000-04.

This research was supported by the National Science Foundation, NASA, U.S. Department of Energy, and other government agencies. The lead author was Christopher Schwalm at Northern Arizona University. Other collaborators were from the University of Colorado, University of California at Berkeley, University of British Columbia and San Diego State University.


Record high of 111 degrees for Little Rock
Triple-digit heat intensified across Arkansas on Monday, setting records in at least two cities and increasing the danger for wildfires.


30 July, 2012

Temperatures exceeded 100 in some areas, and are expected to stick around for much of the week. Low humidity also is settling in, increasing the threat for wildfires.

The daytime high reached 111 degrees in Little Rock, which not only broke the date's record but marked the third-highest temperature ever recorded in the state's capital city. The previous record for July 30 was 108 degrees in 1986.

Little Rock reached 114 degrees last year on Aug. 3, the city's hottest day in 132 years of records. The city's second-highest temperature on record occurred July 31, 1986, when it hit 112 degrees.

Also Monday, a record was set in Jonesboro, where the mercury peaked at 104, a degree higher than the record set in 1986.

National Weather Service senior forecaster Joe Goudsward warned that little relief from the high temperatures is expected soon....



Phoenix covered in blanket of dust for second time in a week as massive cloud rolls in from desert.


30 July, 2012

A second cloud of yellow in less than a week overwhelmed suburban Phoenix on Sunday, mixing with torrential rains and gusty winds that wreaked havoc on midday traffic in the area.

The thick wall of dust, known as a haboob, which is Arabic for 'strong wind,' was seen making its way through the town of Laveen about eight miles southwest of downtown Phoenix.

The greater Phoenix area and northwest and north central Pinal County were under a dust storm warning that expired at 7pm on Sunday.
Second coming: A large dust cloud was seen making its way through the Phoenix suburb of Laveen on Sunday
Second coming: A large dust cloud was seen making its way through the Phoenix suburb of Laveen on Sunday

This comes just days after an enormous dust cloud measuring around 2,000 feet tall and almost 100km wide swept over the city, traveling at 35mph. The dust cut power to some 9,000 homes and caused disruptions at the local airport.
Caused by Arizona's monsoon season which begins in early June and runs through till the end of September, haboob's only occur in Africa, the Middle East, Australia and Phoenix, Arizona.

Known as the granddaddy of dust storms, the haboob is a rare event and is caused by loose dust being blown upwards in the absence of rain and collecting skywards where it is then propelled by another more distant thunderstorm brewing behind it.
 
Despite some of the 1.5 million residents of Phoenix objecting to the term haboob being used, meteorologists in the city confirmed that they have been using the Arabic word to describe the massive dust storms for over 30 years.

'I think what's going on is that we've had a higher frequency of stronger dust storms over the last couple of years and the term has been in play much more because of that,' said Ken Waters of the Phoenix National Weather Service office to KPHO.

Blowing gusts of up to 50 mph at Phoenix Sky Harbor Airport, the haboob is destructive because of the fine dust particles that manage to permeate everywhere during the storm.

The 2,000 foot tall haboob cloud covers the city of Phoenix, Arizona cutting power to 9,000 homes
The 2,000 foot tall haboob cloud covers the city of Phoenix, Arizona cutting power to 9,000 homes

The haboob phenomenon affects Phoenix during the months of June through September which is Arizona's monsoon season
The haboob phenomenon affects Phoenix during the months of June through September which is Arizona's monsoon season

The haboob covered cities in the metropolitan Phoenix area such as Scottsdale, Gilbert, Mesa, Apache Junction, Santan Valley, Chandler, Casa Grande and downtown Phoenix
The haboob covered cities in the metropolitan Phoenix area such as Scottsdale, Gilbert, Mesa, Apache Junction, Santan Valley, Chandler, Casa Grande and downtown Phoenix

Winds were measured as high as 50 miles per hour at Phoenix Sky Harbor Airport which closed for 20 minutes because of the dust cloud

Winds were measured as high as 50 miles per hour at Phoenix Sky Harbor Airport which closed for 20 minutes because of the dust cloud

'The dust gets into everything ... It gets into electronics, it gets into every nook and cranny,' said Penn State University meterologist Fred Gadomski to NPR.
Familiar to millions of movie-goers from films such as 'The Mummy' or 'Hidalgo', the Haboob was witnessed by Phoenix New Times freelance photographer Andrew Pielage, who watched the storm unfold from a mountain viewpoint.
'It is one thing to see it from the ground, but when you are on top of a mountain and you still have to look up to see the top of it you really start to grasp the size and magnitude of the haboob,' said Pielage to the Examiner.com.

The haboob temporarily blocked out the sun and covered everything in a layer of dust

The haboob temporarily blocked out the sun and covered everything in a layer of dust

 
An Arizona researcher who studies haboobs said there could be hidden health impacts for millions of people living in the state’s dust zone.

According to William Sprigg, of the University of Arizona’s Institute of Atmospheric Physics, dust storms carry a noxious mix of fungi, heavy metals from pollutants, chemicals and bacteria that could lead to cardiovascular and eye disease, and other illnesses.

We already know the cost of these storms in general,’ he told the Arizona Republic. ‘I would like to see a much more thorough examination of the effects of the dust on the region.’


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