US National Oceanic and Atmospheric Administration
Climate Test Bed Joint Seminar Series (2009-2010)
NCEP, Camp Springs, Maryland, 15 December 2009

Reconstruction of 20th Century North American Droughts Reveals a Key Role for Atlantic Basin Temperatures

Sumant Nigam

Department of Atmospheric & Oceanic Science and

Earth System Science Interdisciplinary Center (ESSIC)

University of Maryland, College Park, MD


The Great Plains of North America are susceptible to multi-year droughts, such as the 1930s ‘Dust Bowl’. The droughts have been linked to SST variability in the Pacific and the Atlantic but the relative contribution of the basins in generation of prominent 20th century droughts (and wet episodes) is yet to be evaluated, in part, because the SST-forced dynamical models of the atmosphere – a common investigative tool – remain challenged in simulation of regional hydroclimate variability.

Here we adopt a statistical approach rooted in a new spatiotemporal analysis of 20th century SST variations and related drought links, which leads to remarkable reconstruction of the major dry and wet episodes over North America; attesting to the extent of the SST influence and facilitating evaluation of the basin contributions.

We find the Atlantic SSTs, tropical and extratropical, to be particularly influential; more than previously indicated, and often, more than the Pacific ones. Statistical drought reconstruction is provided a dynamical foundation from the extraction of SST-circulation links from a nearly century-long circulation record based, in part, on the recent upper-air meteorological analysis of the 1908-1948 period. The links show modulation of moisture transports to be important for drought generation, particularly in the fall. Rudimentary decadal projections based on phase-persistence of multidecadal SST variability suggest wetness over the central-northern Plains in spring-summer and drought conditions in fall.

Pacific and Atlantic SSTs evidently exert a profound influence on North American hydroclimate on decadal timescales, especially, in spring and fall; an influence not fully represented in present-day dynamical models of the atmosphere.

Contact  Sumant Nigam