Two types of North American droughts related to different atmospheric circulation patterns

Burgdorf, Angela-Maria; Brönnimann, Stefan; Franke, Jörg (2019). Two types of North American droughts related to different atmospheric circulation patterns. Climate of the past, 15(6), pp. 2053-2065. Copernicus Publications 10.5194/cp-15-2053-2019

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Proxy-based studies suggest that the southwestern USA is affected by two types of summer drought, often termed Dust Bowl-type droughts and 1950s-type droughts. The spatial drought patterns of the two types are distinct. It has been suggested that they are related to different circulation characteristics, but a lack of observation-based data has precluded further studies. In this paper, we analyze multi-annual summer droughts in North America back to 1600 in tree-ring-based drought reconstructions and in a global, monthly three-dimensional reconstruction of the atmosphere. Using cluster analysis of drought indices, we confirm the two main drought types and find a similar catalog of events as previous studies. These two main types of droughts are then analyzed with respect to 2 m temperatures (T2m), sea-level pressure (SLP), and 500 hPa geopotential height (GPH) in boreal summer. 1950s-type droughts are related to a stronger wave train over the Pacific–North American sector than Dust Bowl-type droughts, whereas the latter show the imprint of a poleward-shifted jet and establishment of a Great Plains ridge. The 500 hPa GPH patterns of the two types differ significantly not only over the contiguous United States and Canada but also over the extratropical North Atlantic and the Pacific. Dust Bowl-type droughts are associated with positive GPH anomalies, while 1950s-type droughts exhibit strong negative GPH anomalies. In comparison with 1950s-type droughts, the Dust Bowl-type droughts are characterized by higher sea-surface temperatures (SSTs) in the northern North Atlantic. Results suggest that atmospheric circulation and SST characteristics not only over the Pacific but also over the extratropical North Atlantic affect the spatial pattern of North American droughts.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Climatology
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography

UniBE Contributor:

Burgdorf, Angela-Maria; Brönnimann, Stefan and Franke, Jörg

Subjects:

900 History > 910 Geography & travel

ISSN:

1814-9324

Publisher:

Copernicus Publications

Funders:

[18] European Research Council
[42] Schweizerischer Nationalfonds

Projects:

[UNSPECIFIED] PALAEO-RA
[UNSPECIFIED] RE-USE

Language:

English

Submitter:

André Hürzeler

Date Deposited:

13 Feb 2020 14:31

Last Modified:

13 Feb 2020 14:31

Publisher DOI:

10.5194/cp-15-2053-2019

BORIS DOI:

10.7892/boris.139395

URI:

https://boris.unibe.ch/id/eprint/139395

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