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    Sahara Dust In European Skies
    By Patrick Lockerby | April 8th 2011 08:12 PM | 6 comments | Print | E-mail | Track Comments
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    Retired engineer, 60+ years young. Computer builder and programmer. Linguist specialising in language acquisition and computational linguistics....

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    Sahara Dust In European Skies

    The skies over southern England were hazy on Friday April 08 2011.  In the evening the usual colors of sunset were absent.  A muddy grey-brown haze could be seen along the horizon.  That haze was caused by dust from the Sahara.


    Dust from Sahara over Biscay, the English Channel and Ireland


    Dust cloud from Sahara off the coast of Portugal

    Dust from the Sahara can be lifted to high altitudes in the SAL - Saharan Air Layer.  The dust is then carried by winds to distant lands and seas.  The current dust cloud is moving up the Atlantic, bringing hazy skies to Portugal, Spain, France, Britain and Ireland. 
    The SAL can have a significant negative impact on tropical cyclone intensity and formation. Its dry air can act to weaken a tropical cyclone by promoting downdrafts around the storm, while its strong winds can substantially increase the vertical wind shear in and around the storm environment. It is not yet clear what effect the SAL's dust has on tropical cyclone intensity, though some recent studies have suggested that it can actually impact the formation of clouds.

    The SAL can cover an area the size of the continental U.S. and has been tracked as far west as the Caribbean Sea, Central America, and the Gulf of Mexico.
    http://www.aoml.noaa.gov/hrd/tcfaq/A17.html
    Atmospheric dust is studied as an important part of climate science.  It can affect regional weather systems.
    People that live in Florida would expect the sands from the state beaches to blow into the air, and usually don't think of the sands and dust from the Saharan Desert twirling around them. However, winds do carry the desert dust across the Atlantic Ocean, and scientists have been studying what they do to Florida Thunderstorms.
    http://www.nasa.gov/vision/earth/lookingatearth/florida_dust.html

    Atmospheric dust can also affect global climate, through the planet's energy budget and the carbon cycle.
    The global dust budget has been recognized as an important research topic related to the atmospheric environment and climate. Mineral dust aerosol can cause air quality hazards such as visibility impairment and respiratory problems, which can pose risks to human health and society. Mineral dust aerosols also play an important role in the Earth's climate in several ways, including exerting a significant direct and indirect influence on the atmospheric radiation balance. They do so directly through scattering and absorbing shortwave and longwave radiation, and indirectly by acting as cloud condensation nuclei or ice nuclei and modifying the optical properties of clouds. In addition, dust aerosol can serve as a reaction surface for reactive gases, thus affecting atmospheric photochemistry. When these aerosols falls onto the ocean, the iron content in dust acts as a nutrient for marine phytoplankton and can thus enhance photosynthesis, in turn influencing the global carbon cycle.
    http://www.eoearth.org/article/Global_dust_budget
    Although this dust is abrasive, it is much less of a threat to aviation than the dust from a volcanic eruption.  Whereas volcanic dust melts in a jet engine and coats the moving parts, sand needs a higher temperature to melt, and so is merely passed through a jet engine.  In the case of piston engines, in the air or on land, desert dust can quickly choke an air filter.  The effect can range from the stalling of the engine to the somewhat trivial need to change an air filter more often.

    Dust is a nuisance to humans, but it is of great benefit to many organisms.  Dust from the Sahara contains nutrients which promote the growth of some marine organisms, helping reduce atmospheric CO2.  Dust carried across the entire Atlantic can provide nutrients to the tropical rain forests.

    Images source:
    http://rapidfire.sci.gsfc.nasa.gov/gallery/

    Further reading:

    http://news.bbc.co.uk/1/hi/7228081.stm

    Observations of mesoscale and boundary-layer scale circulations affecting dust transport and uplift over the Sahara
    http://www.faam.ac.uk/index.php/publications?view=publication&task=show&id=471

    Electric sand findings could lead to better climate models
    http://www.eurekalert.org/pub_releases/2008-01/uom-esf010708.php

    Comments

    Stellare
    I just saw (Norwegian news) that a freak sandstorm caused some serious havoc in Germany, too. Amazing what sandstorms can, small or large dimensions.

    Here it is described on BBC.
    Bente Lilja Bye is the author of Lilja - A bouquet of stories about the Earth
    logicman
    Hi, Bente.  I just logged in to add a comment on the German autobahn pile-up, but you beat me to it.

    A freak sandstorm has caused a pile-up on the A19 autobahn between Rostock and Güstrow.  It has been described as the most serious accident in Mecklenburg-Western Pomerania's history.  It appears that soil from farms was lofted in freak weather conditions, causing drastically reduced visibility on the motorway.  The 80 vehicle pile-up left 8 dead and more than 130 injured.  Many vehicles were completely destroyed by fire.

    The German Weather Service (DWD) blamed the sandstorm on high winds and extremely dry weather.

    "There had not been abundant rain in the region for an extended period of time – that means the wind does not have to reach hurricane strength to produce sandstorms like this," meteorologist Angela Richter said.

    She added that winds at the site of the crash in Kavelstorf had been between 72 and 86 kilometres per hour. In areas further west, forest fire warnings have already been issued due to dry conditions.

    "Storms like this are not rare in the north," DWD spokesman Gerhard Lux said. "It was more a chain of unfortunate circumstances that led to the pile-up."

    The German Weather Service said the storm was, however, atypical in that it had pushed unusually far inland from the coast.

    Source: http://www.thelocal.de/national/20110409-34293.html
    Hi Patrick,

    This wind-pattern also were able to penetrate all the way up to "cold" Norway as well, ruining several roofs, both schools, firestations, mayor's house etc, and the most rare about this weather was not the wind intensity in itself, but the scale of it thus far inland, 26-28 m/s was measured far inland, and some had not witnessed this intensity since a gale back in '92. (Myself I had to climb the roofs at work to help them stay were they were meant to be:-).

    Personally I have a feeling we will have to face more extreme weather in the era we're about to enter!

    Patrick: How much more sand is it left in Sahara? I know much of sahara consist of rock and gravel...

    Erosion and modern agriculture is partly causing these obstacles, creating both erosion and obstacle as above described!
    And we all remember the Great Dust-bowls in the 20-30 ties over there...

    logicman
    Christoffer: thanks for the info.  Can you post a link to a news story?  It doesn't have to be in English.  Thanks.

    ...Drought Continues to Intensify Across Large Portion of Country...
    Drought continues to be a serious problem across a large portion of the country. The April through June 2011 U.S. Seasonal Drought Outlook indicates that drought is expected to intensify or persist across the Southwest, Southern Plains and other areas. The latest U.S. Drought Monitor shows that nearly 1/3 of the contiguous U.S. is currently experiencing drought conditions, with exceptional drought (D4) conditions indicated for the contiguous U.S. for the first time since November 2009.
    http://www.weather.gov/

    Severe weather alerts are current across much of the USA.  For example, this high wind and dust warning just posted for Albuquerque:
    THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH AND CENTRAL
    NEW MEXICO.

    .DAY ONE...TODAY AND TONIGHT

    A RED FLAG WARNING IS IN EFFECT FROM 10 AM TO 9 PM MDT FOR AREAS
    ALONG AND EAST OF A COLFAX TO GUADALUPE TO ROOSEVELT COUNTY LINE.
    LOW HUMIDITIES COMBINED WITH STRONG WINDS WILL CREATE EXTREME FIRE
    WEATHER CONDITIONS.

    STRONG TO DAMAGING WINDS WILL DEVELOP THIS MORNING ACROSS MUCH OF
    NORTHERN AND CENTRAL NEW MEXICO. WIND SPEEDS WILL BE HIGHEST ALONG
    AND EAST OF AN UPPER GILA TO SANGRE DE CRISTO MOUNTAINS LINE. WIND
    SPEEDS OF 30 TO 45 MPH...WITH GUSTS UP TO 6O OR 65 MPH ARE LIKELY.
    WINDS WILL REMAIN STRONG THROUGH THE OVERNIGHT HOURS. IMPACTS WILL
    INCLUDE POSSIBLE PROPERTY DAMAGE...EXTREMELY DANGEROUS CROSS WINDS
    AND WIDESPREAD REDUCTIONS IN BLOWING DUST.

    .DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

    CRITICAL FIRE WEATHER CONDITIONS ARE LIKELY IN THE EASTERN PLAINS
    OF NEW MEXICO FROM LATE SUNDAY MORNING THROUGH THE EARLY EVENING
    HOURS DUE TO THE COMBINATION OF LOW HUMIDITIES AND STRONG SURFACE
    WINDS.

    STRONG TO POTENTIALLY DAMAGING WINDS ARE LIKELY SUNDAY IN EASTERN
    NEW MEXICO. WIND SPEEDS OF 30 TO 45 MPH...WITH GUSTS UP TO 6O OR
    65 MPH ARE LIKELY. IMPACTS WILL INCLUDE POSSIBLE PROPERTY DAMAGE...
    DANGEROUS CROSS WINDS AND REDUCED VISIBILITIES IN BLOWING DUST.
    more >>>http://forecast.weather.gov/...Albuquerque Hazardous Weather Outlook

    Note: I think that 'widespread reductions in blowing dust' should read 'reductions in visibility due to blowing dust'.


    Caution:
    In extremely dusty conditions drivers should be aware that their vehicle's air filter can rapidly choke with dust - especially in the case of an air filter which is overdue for replacement.  In dense traffic and sudden low visibility the sudden loss of power may contribute to the hazards of the situation.

    Remember: vehicles which were designed or modified to cope with desert conditions have specially adapted air filters.  The chances are that your vehicle doesn't.  If you must drive in an area which is experiencing dust storms: change the air filter before driving.  Take care!
    Also in parts of the east of southern Norway have experienced a very dry March, but thanks to a rather deep snowlayer in the lower parts, that have vanished almost entirely now due to a rocketing start of April, we haven't as in Germany come that far into the agriculture season yet, but the dust where sure blowing feriously anyway, AND the whole ice in the Oslofjord and Bunnefjord (where I'm almost located, and also Amundsen in an other century...) did break up and disappered in a single day! (Something for the Nares-strait maybe...)

    http://www.storm.no/nyheter/storm-paa-oestlandet-3465135.html
    http://www.abcnyheter.no/nyheter/110408/storm-pa-ostlandet
    http://www.nrk.no/nyheter/distrikt/sorlandet/1.7586151
    http://dt.no/nyheter/tak-blaste-av-ungdomsskole-1.6159266

    Much here in norwegian Patrick, but that will just be a minor challenge for you Patrick; and besides I've come to believe your deep into the Old-Norse history and language, right!?

    World-wide erosion should be paid more attention to, I suppose much land have to be degraded from intensive to extensive farming due to human (machinery) mistreatment...

    Then the Sahara dust at last hit Norway, all the way up in the north actually!
    http://www.hblad.no/nyheter/article445923.ece

    Further south in the "greater-Oslo" region, we witnessed the earliest "summer" in almost 40 years, passing 21,3 C in Kongsberg, which also smashed a 105 year old record for this particular date!
    http://www.verogvind.net/readmore.asp?readmoreid=2974

    Are you able to digest this norwegian Patrick? :-D