The global footprint of persistent extra‐tropical drought in the instrumental era

Abstract

The major North American droughts as per instrumental records are shown to be part of a larger, global pattern of low‐frequency drought variability. Drought in western North America during the 1850s–1860s, 1870s, 1890s, 1930s and 1950s, is shown to coincide with the occurrence of prolonged dry spells in parts of Europe, southern South America and western Australia. Tropical land regions are mostly wet during these periods, with the exception of central east Africa, southern India and Sri Lanka, which are dry. The recent 1998–2003 period of drought in western North America reveals a similar global hydroclimatic ‘footprint’ with the exception of a wet southern South America and continued dry conditions in the Sahel. Common to each of the six droughts is the persistence of anomalously cool east central tropical Pacific sea surface temperatures (SSTs). For the 1998–2003 case, the warming of SSTs everywhere outside of the east central tropical Pacific may be influencing precipitation and masking the influence of persistent precipitation anomalies driven from the tropical Pacific alone. In general, examination of these major historical extra‐tropical droughts reveals a hemispherically and, in the extra‐tropics, a zonally symmetric pattern consistent with forcing from the Tropics.Ensembles of model simulations forced by observed SSTs globally (Global Ocean Global Atmosphere, GOGA) and only within the tropical Pacific (Pacific Ocean Global Atmosphere‐Mixed Layer, POGA‐ML) are both able to capture the global pattern of the persistent extra‐tropical drought regimes since the mid‐nineteenth century. This implies that the recently demonstrated link between SST forcing and drought in North America is in fact only one part of a global hydroclimatic response to the persistence of cool SST anomalies in the tropical Pacific. Indian Ocean SST forcing is required to capture the droughts in central east Africa. Over Europe, the modelled, low‐frequency precipitation signal is unrealistically ENSO dominated, as the model does not faithfully reproduce the observed history of low‐frequency NAO variability. Overall, our results suggest that the global pattern of persistent drought appears to be a low‐frequency version of interannual ENSO‐forced variability. Copyright © 2008 Royal Meteorological Society

Drought Analysis in Europe and in the Mediterranean Basin Using the Standardized Precipitation Index

“…For example, due to the NAO Results of this study, which evidenced different trends between continental Europe and the Mediterranean basin, confirm past studies. Indeed, while in continental Europe dry periods have been identified in the 20th century [63][64][65], the 2000s have been characterized by an increase in drought frequency and severity in Southern Europe and the Mediterranean area [66,67], but also in some areas of Russia. In particular, Northern and Eastern Europe showed the highest drought frequency and severity from the early 1950s to the mid-1970s while Southern and Western Europe showed the highest drought frequency and severity from the early 1990s onwards [68,69].…”

A review of droughts on the African continent: a geospatial and long-term perspective

“…There are few studies which attempt to cover more than one region (e.g. Calow et al, 2010;Herweijer and Seager, 2008;Rojas et al, 2011;Naumann et al, 2012;Tadesse et al, 2008;Verschuren, 2004). These and many other studies are comprehensively reviewed and discussed in the following sections.…”

“…Nicholson, 2000). Many studies attempted to investigate the natural causes that could be associated with droughts in Africa (Caminade and Terray, 2010;Dai, 2011Dai, , 2013Giannini et al, 2008Hastenrath et al, 2007;Herweijer and Seager, 2008;Jury et al, 1996;Kerr, 1985;Lebel et al, 2009;Manatsa et al, 2008;Nicholson, 2000;Richard et al, 2001;Shanahan et al, 2009;Tierney et al, 2013;VicenteSerrano, 2012;Zeng, 2003). Some of them also focus on anthropogenic factors, such as climate change, aerosol emissions, land use practices and resulting land-atmosphere interactions, contributing to drought inducing mechanisms (e.g.…”

Nature and causes of the 2002 to 2004 drought in the southwestern United States compared with the historic 1953 to 1957 drought

“…Recent research has shown that multi-year La Niña events are associated with persistent drought in the western USA (Cole et al 2002) as well as in southern Europe, southern South America, and western Australia (Herweijer & Seager 2008). A single-year La Niña is generally associated with a 15 to 30% decrease in winter precipitation, but it has a negligible effect on the summer monsoon.…”