Twentieth-Century Drought in the Conterminous United States

Abstract

Droughts can be characterized by their severity, frequency and duration, and areal extent. Depth–area–duration analysis, widely used to characterize precipitation extremes, provides a basis for the evaluation of drought severity when storm depth is replaced by an appropriate measure of drought severity. Gridded precipitation and temperature data were used to force a physically based macroscale hydrologic model at 1/2° spatial resolution over the continental United States, and construct a drought history from 1920 to 2003 based on the model-simulated soil moisture and runoff. A clustering algorithm was used to identify individual drought events and their spatial extent from monthly summaries of the simulated data. A series of severity–area–duration (SAD) curves were constructed to relate the area of each drought to its severity. An envelope of the most severe drought events in terms of their SAD characteristics was then constructed. The results show that (a) the droughts of the 1930s and 1950s were the most severe of the twentieth century for large areas; (b) the early 2000s drought in the western United States is among the most severe in the period of record, especially for small areas and short durations; (c) the most severe agricultural droughts were also among the most severe hydrologic droughts, however, the early 2000s western U.S. drought occupies a larger portion of the hydrologic drought envelope curve than does its agricultural companion; and (d) runoff tends to recover in response to precipitation more quickly than soil moisture, so the severity of hydrologic drought during the 1930s and 1950s was dampened by short wet spells, while the severity of the early 2000s drought remained high because of the relative absence of these short-term phenomena.

Future discharge drought across climate regions around the world modelled with a synthetic hydrological modelling approach forced by three general circulation models

“…At large scales, global hydrological models (GHMs) are used to produce runoff time series, which are then used for hydrological drought assessment. At the continental scale, Andreadis et al (2005) investigated runoff drought in the United States and Prudhomme et al (2011) studied European runoff drought. Forzieri et al (2014) project for the A1B scenario that future drought in streamflow will increase in many European regions, except for North and Northeast Europe.…”

A spatio‐temporal structure‐based approach to drought characterisation

“…In light of these difficulties, this paper proposes a simple agglomerative technique to identify large-scale coherent space-time drought events. Andreadis et al, (2005) describe a spatial identification procedure in which all pixels that have a soil moisture (or runoff) percentile value below 20% are considered as being under drought. Those pixels are then classified into drought classes using a simple clustering algorithm.…”

Global projections of changing risks of floods and droughts in a changing climate

“…However, low river flows (streamflow droughts) must also be considered, because many regions are irrigated with river water. Andreadis et al (2005) used a land surface model (LSM) driven by historical atmospheric data on a 1/2° grid to estimate water budget in the 20th century over the USA and found that the shortage of storages in soil moisture and in runoff were not always coincident in space and time. This study implies that low river flows may not be estimated simply from vertical water and energy balances, such as soil moisture or precipitation minus evapotranspiration.…”