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Kristopher B. Karnauskas, Alfredo Ruiz-Barradas, Sumant Nigam, and Antonio J. Busalacchi

1. Introduction Estimates of annual economic loss in the United States directly attributable to drought are in the range of $6–8 billion. In response to growing concern from local and national leadership, the National Integrated Drought Information System (NIDIS) has been established to synthesize the work of modeling and reanalysis communities with that of monitoring and application communities. The most widely used index to monitor drought conditions in the United States is the Palmer drought

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Sergio M. Vicente-Serrano, Santiago Beguería, Jorge Lorenzo-Lacruz, Jesús Julio Camarero, Juan I. López-Moreno, Cesar Azorin-Molina, Jesús Revuelto, Enrique Morán-Tejeda, and Arturo Sanchez-Lorenzo

1. Introduction Drought is among the most complex climatic phenomena affecting society and the environment ( Wilhite 1993 ). The root of this complexity is related to the difficulty of quantifying drought severity since we identify a drought by its effects or impacts on different types of systems (agriculture, water resources, ecology, forestry, economy, etc.), but there is not a physical variable we can measure to quantify droughts. Thus, droughts are difficult to pinpoint in time and space

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Richard Seager

1. Introduction After the 1997–98 El Niño, drought struck across almost the entire United States, northern Mexico, and the Canadian Prairies. At its most severe, between 1999 and 2002, drought stretched from the Pacific Ocean to the Atlantic Ocean causing forest fires in the American Southwest and Quebec and causing widespread alarm about water resources, even in New York City. The drought ended in eastern North America in the fall of 2002 but continued farther west. In the winter of 2004

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Yeonsang Hwang and Gregory J. Carbone

1. Introduction Drought is part of natural climate variability, but anticipating its occurrence remains challenging because some parts of the hydrologic cycle (e.g., precipitation, soil moisture, or groundwater level) are not easily forecast. Yet, the desire to mitigate impacts on agriculture and water resources ( Steinemann 2006 ) has resulted in the development of drought prediction methods. As long as perfect drought forecasts with long lead times remain elusive, predictions should include

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Matías Méndez and Víctor Magaña

1. Introduction Persistent or prolonged droughts (duration of more than one year) have had negative consequences on the socioeconomic life of Mexico ( Endfield et al. 2004 ; Endfield and Fernández-Tejedo 2006 ; Acuña-Soto et al. 2000 , 2002 ). For example, some studies suggest that the collapse of the Mayan empire was related to a major drought episode in the eighth century ( Culbert 1973 ; Hodell et al. 1995 , 2007 ). The so-called mega-drought in the sixteenth century, described through

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Philip J. Pegion and Arun Kumar

1. Introduction Toward identifying the causal mechanism for the occurrences of long-term droughts, the Drought Working Group (DWG) of the U.S. Climate Variability and Predictability component of the World Climate Research Programme (CLIVAR) was formed in December 2006. The approach of the DWG was to coordinate evaluations of existing model simulations and to also coordinate new experiments designed to address some of the outstanding questions related to drought variability and predictability

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Karin L. Gleason, Jay H. Lawrimore, David H. Levinson, Thomas R. Karl, and David J. Karoly

. [For additional background information regarding the original CEI, please see Karl et al. (1996) .] The CEI is composed of five indicators, or steps, that illustrate possible extremes in monthly mean maximum and minimum temperature, extreme 1-day precipitation, days with/without precipitation, and the Palmer Drought Severity Index (PDSI) on an annual or seasonal basis (see the appendix for a detailed explanation of how each indicator is calculated). Extremes for each indicator are defined as

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Suryachandra A. Rao, Hemantkumar S. Chaudhari, Samir Pokhrel, and B. N. Goswami

1. Introduction Each Indian summer monsoon exhibits different characteristics and poses several challenges to scientists to unravel the mechanisms of its variability. Of particular interest is the regional distribution of rainfall anomalies during “normal” monsoon years. During years of extreme droughts or floods, the rainfall anomaly tends to be homogeneous over the whole country ( Shukla 1987 ; Mooley and Shukla 1987 ). While during normal monsoon years, the rainfall anomaly tends to be

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Mary Noel, Deborah Bathke, Brian Fuchs, Denise Gutzmer, Tonya Haigh, Michael Hayes, Markéta Poděbradská, Claire Shield, Kelly Smith, and Mark Svoboda

Motivation Linking drought impact information to drought monitoring has long been cited as a need in the drought community ( Western Governors Association 2004 ; Hayes et al. 2011 ; Meadow et al. 2013 ; Lackstrom et al. 2017 ). By associating qualitative descriptions of drought impacts with levels of drought, a more complete characterization of drought can be formed to improve drought planning, reporting, and early warning tools. The United States Drought Monitor ( USDM ; Svoboda et al

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Steven M. Quiring

1. Introduction Drought is a complex phenomenon that is difficult to accurately describe because its definition is both spatially variant and context dependent. Therefore a uniform method for defining and monitoring drought conditions and quantifying the severity of drought does not exist. There are two main types of drought definitions: conceptual and operational. Conceptual definitions are formulated in general terms and they are used to help explain what a drought is. Operational definitions

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