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University of Massachusetts Lowell (2011)

Aspects of oceanic forcing of drought over Southwest Asia and the United States

Hoell, Andrew

Titre : Aspects of oceanic forcing of drought over Southwest Asia and the United States

Auteur : Hoell, Andrew

Université de soutenance : University of Massachusetts Lowell

Grade : Doctor of Philosophy (PhD) 2011

Résumé
An exceptionally severe drought affected much of the Northern Hemisphere mid-latitudes during 1998 – 2002, with maxima over Southwest Asia and the United States. Previous research has suggested that the oceans played an important role in the hemispheric drought, with oceanic links to tropical Indo-west Pacific Ocean convection highlighted as important for Southwest Asia, and several additional ocean regions suggested as important for the United States. Here, the regional and hemispheric circulation response to tropical Indo-west Pacific Ocean convection is examined for both Southwest Asia and the United States, and the relative importance of individual sea surface temperature areas are explored for United States precipitation. For Southwest Asia, the regional thermodynamic forcing of precipitation and the Northern Hemisphere circulation are related to the leading pattern of Indian Ocean precipitation and its intraseasonal and interannual contributions. Both intraseasonal and interannual timescales are associated with baroclinic Gill-Matsuno-like circulation responses extending over southern Asia, but the interannual component also has a strong equivalent-barotropic circulation. A stationary barotropic Rossby wave extending over North America is associated with interannual tropical Indo-west Pacific Ocean convection and is supported by barotropic ray tracing. For United States regions, historical SST and precipitation links are identified for 1948 – 1997, and the importance of these links are assessed during the 1998 – 2002 drought using a linear regression model. The reconstructed precipitation has good correspondence for the Southwest and Southeast United States, but is not able to reproduce precipitation variability over the Northwest and Central United States, especially Texas.

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Page publiée le 13 mai 2012, mise à jour le 17 novembre 2018