YaBeSH Engineering and Technology Library

    • Journals
    • PaperQuest
    • YSE Standards
    • YaBeSH
    • Login
    View Item 
    •   YE&T Library
    • AMS
    • Journal of Climate
    • View Item
    •   YE&T Library
    • AMS
    • Journal of Climate
    • View Item
    • All Fields
    • Source Title
    • Year
    • Publisher
    • Title
    • Subject
    • Author
    • DOI
    • ISBN
    Advanced Search
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Archive

    The Effect of Tropical Atlantic Heating Anomalies upon GCM Rain Forecasts over the Americas

    Source: Journal of Climate:;1990:;volume( 003 ):;issue: 002::page 189
    Author:
    Buchmann, Julio
    ,
    Paegle, Jan
    ,
    Buja, Lawrence E.
    ,
    Dickinson, Robert E.
    DOI: 10.1175/1520-0442(1990)003<0189:TEOTAH>2.0.CO;2
    Publisher: American Meteorological Society
    Abstract: Severe droughts occurred over eastern sections of North America and central sections of South America in 1986 and 1988. We summarize data suggesting that both periods were characterized by above-normal tropical Atlantic sea surface temperatures and convection, and investigate the response of a general circulation model to positive heating anomalies in the tropical Atlantic sector. An eight-case control ensemble of 30 day global predictions is made starting from the atmospheric state observed on 1 January of each year from 1977 through 1984. The same eight cases are integrated in a second experimental ensemble that is identical to the first control ensemble, except that a heating term is added to the thermodynamic equation in a region centered at 30°W, 6.6°N. This is intended to simulate the latent heating of enhanced tropical Atlantic convection. The third ensemble is identical to the second, except the heating is centered at 6.6°S. Both heated ensembles produce reductions of forecast precipitation over most of North and South America, but these appear to have greater statistical significance over North America. Here the greatest precipitation reductions are forecast over the southern and eastern United States, and this response does not change substantially between the two experiments. The South American response is more sensitive to the placement of the heating anomaly. When the anomaly is located north of the equator, drying occurs over northeast Brazil; meanwhile this region receives increased rainfall when the anomaly is located south of the equator. Both experiment ensembles display a region of reduced rainfall over the Andes Mountains, and over southern portions of Brazil. However, only the former region is statistically significant above the 95% confidence level. The present usage of real initial data and an ensemble of cases permits us to draw quantitatively meaningful estimates of the time scale of response and case-to-case variability. For presently tested cases, the South American response is evident by day 5, but exhibits substantial intersample variability, and the North American response is fully established by day 10, and exhibits less intersample variability. The model drying effects can be explained only partly by enhanced local subsidence; much of the rainfall reduction appears to be related to a reorientation of the synoptic scale wave pattern in which the lower tropospheric circulation is unfavorable for water vapor inflow from source regions over the tropical Atlantic and Amazon Basin.
    • Download: (1.612Mb)
    • Show Full MetaData Hide Full MetaData
    • Item Order
    • Go To Publisher
    • Price: 5000 Rial
    • Statistics

      The Effect of Tropical Atlantic Heating Anomalies upon GCM Rain Forecasts over the Americas

    URI
    http://yetl.yabesh.ir/yetl1/handle/yetl/4174822
    Collections
    • Journal of Climate

    Show full item record

    contributor authorBuchmann, Julio
    contributor authorPaegle, Jan
    contributor authorBuja, Lawrence E.
    contributor authorDickinson, Robert E.
    date accessioned2017-06-09T15:11:13Z
    date available2017-06-09T15:11:13Z
    date copyright1990/02/01
    date issued1990
    identifier issn0894-8755
    identifier otherams-3678.pdf
    identifier urihttp://onlinelibrary.yabesh.ir/handle/yetl/4174822
    description abstractSevere droughts occurred over eastern sections of North America and central sections of South America in 1986 and 1988. We summarize data suggesting that both periods were characterized by above-normal tropical Atlantic sea surface temperatures and convection, and investigate the response of a general circulation model to positive heating anomalies in the tropical Atlantic sector. An eight-case control ensemble of 30 day global predictions is made starting from the atmospheric state observed on 1 January of each year from 1977 through 1984. The same eight cases are integrated in a second experimental ensemble that is identical to the first control ensemble, except that a heating term is added to the thermodynamic equation in a region centered at 30°W, 6.6°N. This is intended to simulate the latent heating of enhanced tropical Atlantic convection. The third ensemble is identical to the second, except the heating is centered at 6.6°S. Both heated ensembles produce reductions of forecast precipitation over most of North and South America, but these appear to have greater statistical significance over North America. Here the greatest precipitation reductions are forecast over the southern and eastern United States, and this response does not change substantially between the two experiments. The South American response is more sensitive to the placement of the heating anomaly. When the anomaly is located north of the equator, drying occurs over northeast Brazil; meanwhile this region receives increased rainfall when the anomaly is located south of the equator. Both experiment ensembles display a region of reduced rainfall over the Andes Mountains, and over southern portions of Brazil. However, only the former region is statistically significant above the 95% confidence level. The present usage of real initial data and an ensemble of cases permits us to draw quantitatively meaningful estimates of the time scale of response and case-to-case variability. For presently tested cases, the South American response is evident by day 5, but exhibits substantial intersample variability, and the North American response is fully established by day 10, and exhibits less intersample variability. The model drying effects can be explained only partly by enhanced local subsidence; much of the rainfall reduction appears to be related to a reorientation of the synoptic scale wave pattern in which the lower tropospheric circulation is unfavorable for water vapor inflow from source regions over the tropical Atlantic and Amazon Basin.
    publisherAmerican Meteorological Society
    titleThe Effect of Tropical Atlantic Heating Anomalies upon GCM Rain Forecasts over the Americas
    typeJournal Paper
    journal volume3
    journal issue2
    journal titleJournal of Climate
    identifier doi10.1175/1520-0442(1990)003<0189:TEOTAH>2.0.CO;2
    journal fristpage189
    journal lastpage208
    treeJournal of Climate:;1990:;volume( 003 ):;issue: 002
    contenttypeFulltext
    DSpace software copyright © 2002-2015  DuraSpace
    نرم افزار کتابخانه دیجیتال "دی اسپیس" فارسی شده توسط یابش برای کتابخانه های ایرانی | تماس با یابش
    yabeshDSpacePersian
     
    DSpace software copyright © 2002-2015  DuraSpace
    نرم افزار کتابخانه دیجیتال "دی اسپیس" فارسی شده توسط یابش برای کتابخانه های ایرانی | تماس با یابش
    yabeshDSpacePersian