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    Intensification of North American Megadroughts through Surface and Dust Aerosol Forcing

    Source: Journal of Climate:;2012:;volume( 026 ):;issue: 013::page 4414
    Author:
    Cook, Benjamin I.
    ,
    Seager, Richard
    ,
    Miller, Ron L.
    ,
    Mason, Joseph A.
    DOI: 10.1175/JCLI-D-12-00022.1
    Publisher: American Meteorological Society
    Abstract: ree-ring-based reconstructions of the Palmer drought severity index (PDSI) indicate that, during the Medieval Climate Anomaly (MCA), the central plains of North America experienced recurrent periods of drought spanning decades or longer. These megadroughts had exceptional persistence compared to more recent events, but the causes remain uncertain. The authors conducted a suite of general circulation model experiments to test the impact of sea surface temperature (SST) and land surface forcing on the MCA megadroughts over the central plains. The land surface forcing is represented as a set of dune mobilization boundary conditions, derived from available geomorphological evidence and modeled as increased bare soil area and a dust aerosol source (32°?44°N, 105°?95°W). In the experiments, cold tropical Pacific SST forcing suppresses precipitation over the central plains but cannot reproduce the overall drying or persistence seen in the PDSI reconstruction. Droughts in the scenario with dust aerosols, however, are amplified and have significantly longer persistence than in other model experiments, more closely matching the reconstructed PDSI. This additional drying occurs because the dust increases the shortwave planetary albedo, reducing energy inputs to the surface and boundary layer. The energy deficit increases atmospheric stability, inhibiting convection and reducing cloud cover and precipitation over the central plains. Results from this study provide the first model-based evidence that dust aerosol forcing and land surface changes could have contributed to the intensity and persistence of the central plains megadroughts, although uncertainties remain in the formulation of the boundary conditions and the future importance of these feedbacks.
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      Intensification of North American Megadroughts through Surface and Dust Aerosol Forcing

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    contributor authorCook, Benjamin I.
    contributor authorSeager, Richard
    contributor authorMiller, Ron L.
    contributor authorMason, Joseph A.
    date accessioned2017-06-09T17:05:55Z
    date available2017-06-09T17:05:55Z
    date copyright2013/07/01
    date issued2012
    identifier issn0894-8755
    identifier otherams-79352.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4222123
    description abstractree-ring-based reconstructions of the Palmer drought severity index (PDSI) indicate that, during the Medieval Climate Anomaly (MCA), the central plains of North America experienced recurrent periods of drought spanning decades or longer. These megadroughts had exceptional persistence compared to more recent events, but the causes remain uncertain. The authors conducted a suite of general circulation model experiments to test the impact of sea surface temperature (SST) and land surface forcing on the MCA megadroughts over the central plains. The land surface forcing is represented as a set of dune mobilization boundary conditions, derived from available geomorphological evidence and modeled as increased bare soil area and a dust aerosol source (32°?44°N, 105°?95°W). In the experiments, cold tropical Pacific SST forcing suppresses precipitation over the central plains but cannot reproduce the overall drying or persistence seen in the PDSI reconstruction. Droughts in the scenario with dust aerosols, however, are amplified and have significantly longer persistence than in other model experiments, more closely matching the reconstructed PDSI. This additional drying occurs because the dust increases the shortwave planetary albedo, reducing energy inputs to the surface and boundary layer. The energy deficit increases atmospheric stability, inhibiting convection and reducing cloud cover and precipitation over the central plains. Results from this study provide the first model-based evidence that dust aerosol forcing and land surface changes could have contributed to the intensity and persistence of the central plains megadroughts, although uncertainties remain in the formulation of the boundary conditions and the future importance of these feedbacks.
    publisherAmerican Meteorological Society
    titleIntensification of North American Megadroughts through Surface and Dust Aerosol Forcing
    typeJournal Paper
    journal volume26
    journal issue13
    journal titleJournal of Climate
    identifier doi10.1175/JCLI-D-12-00022.1
    journal fristpage4414
    journal lastpage4430
    treeJournal of Climate:;2012:;volume( 026 ):;issue: 013
    contenttypeFulltext
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    DSpace software copyright © 2002-2015  DuraSpace
    نرم افزار کتابخانه دیجیتال "دی اسپیس" فارسی شده توسط یابش برای کتابخانه های ایرانی | تماس با یابش
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