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  • Author or Editor: Carlos R. Mechoso x
  • Journal of Climate x
  • Global Drought Information System - Drought Characterization, Occurrence, Driving Mechanisms, and Predictability Worldwide (GDIS Worldwide) x
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Belen Rodríguez-Fonseca
,
Elsa Mohino
,
Carlos R. Mechoso
,
Cyril Caminade
,
Michela Biasutti
,
Marco Gaetani
,
J. Garcia-Serrano
,
Edward K. Vizy
,
Kerry Cook
,
Yongkang Xue
,
Irene Polo
,
Teresa Losada
,
Leonard Druyan
,
Bernard Fontaine
,
Juergen Bader
,
Francisco J. Doblas-Reyes
,
Lisa Goddard
,
Serge Janicot
,
Alberto Arribas
,
William Lau
,
Andrew Colman
,
M. Vellinga
,
David P. Rowell
,
Fred Kucharski
, and
Aurore Voldoire

Abstract

The Sahel experienced a severe drought during the 1970s and 1980s after wet periods in the 1950s and 1960s. Although rainfall partially recovered since the 1990s, the drought had devastating impacts on society. Most studies agree that this dry period resulted primarily from remote effects of sea surface temperature (SST) anomalies amplified by local land surface–atmosphere interactions. This paper reviews advances made during the last decade to better understand the impact of global SST variability on West African rainfall at interannual to decadal time scales. At interannual time scales, a warming of the equatorial Atlantic and Pacific/Indian Oceans results in rainfall reduction over the Sahel, and positive SST anomalies over the Mediterranean Sea tend to be associated with increased rainfall. At decadal time scales, warming over the tropics leads to drought over the Sahel, whereas warming over the North Atlantic promotes increased rainfall. Prediction systems have evolved from seasonal to decadal forecasting. The agreement among future projections has improved from CMIP3 to CMIP5, with a general tendency for slightly wetter conditions over the central part of the Sahel, drier conditions over the western part, and a delay in the monsoon onset. The role of the Indian Ocean, the stationarity of teleconnections, the determination of the leader ocean basin in driving decadal variability, the anthropogenic role, the reduction of the model rainfall spread, and the improvement of some model components are among the most important remaining questions that continue to be the focus of current international projects.

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Siegfried D. Schubert
,
Ronald E. Stewart
,
Hailan Wang
,
Mathew Barlow
,
Ernesto H. Berbery
,
Wenju Cai
,
Martin P. Hoerling
,
Krishna K. Kanikicharla
,
Randal D. Koster
,
Bradfield Lyon
,
Annarita Mariotti
,
Carlos R. Mechoso
,
Omar V. Müller
,
Belen Rodriguez-Fonseca
,
Richard Seager
,
Sonia I. Seneviratne
,
Lixia Zhang
, and
Tianjun Zhou

Abstract

Drought affects virtually every region of the world, and potential shifts in its character in a changing climate are a major concern. This article presents a synthesis of current understanding of meteorological drought, with a focus on the large-scale controls on precipitation afforded by sea surface temperature (SST) anomalies, land surface feedbacks, and radiative forcings. The synthesis is primarily based on regionally focused articles submitted to the Global Drought Information System (GDIS) collection together with new results from a suite of atmospheric general circulation model experiments intended to integrate those studies into a coherent view of drought worldwide. On interannual time scales, the preeminence of ENSO as a driver of meteorological drought throughout much of the Americas, eastern Asia, Australia, and the Maritime Continent is now well established, whereas in other regions (e.g., Europe, Africa, and India), the response to ENSO is more ephemeral or nonexistent. Northern Eurasia, central Europe, and central and eastern Canada stand out as regions with few SST-forced impacts on precipitation on interannual time scales. Decadal changes in SST appear to be a major factor in the occurrence of long-term drought, as highlighted by apparent impacts on precipitation of the late 1990s “climate shifts” in the Pacific and Atlantic SST. Key remaining research challenges include (i) better quantification of unforced and forced atmospheric variability as well as land–atmosphere feedbacks, (ii) better understanding of the physical basis for the leading modes of climate variability and their predictability, and (iii) quantification of the relative contributions of internal decadal SST variability and forced climate change to long-term drought.

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