Abstract
Abstract. Drought is a recurring extreme climate event and among the most costly natural disasters in the world. This is particularly true over Canada, where drought is both a frequent and damaging phenomenon with impacts on regional water resources, agriculture, industry, aquatic ecosystems, and health. However, nationwide drought assessments are currently lacking and impacted by limited ground-based observations. This study provides a comprehensive analysis of historical droughts over the whole of Canada, including the role of large-scale teleconnections. Drought events are characterized by the Standardized Precipitation Evapotranspiration Index (SPEI) over various temporal scales (1, 3, 6, and 12 consecutive months, 6 months from April to September, and 12 months from October to September) applied to different gridded monthly data sets for the period 1950–2013. The Mann–Kendall test, rotated empirical orthogonal function, continuous wavelet transform, and wavelet coherence analyses are used, respectively, to investigate the trend, spatio-temporal patterns, periodicity, and teleconnectivity of drought events. Results indicate that southern (northern) parts of the country experienced significant trends towards drier (wetter) conditions although substantial variability exists. Two spatially well-defined regions with different temporal evolution of droughts were identified – the Canadian Prairies and northern central Canada. The analyses also revealed the presence of a dominant periodicity of between 8 and 32 months in the Prairie region and between 8 and 40 months in the northern central region. These cycles of low-frequency variability are found to be associated principally with the Pacific–North American (PNA) and Multivariate El Niño/Southern Oscillation Index (MEI) relative to other considered large-scale climate indices. This study is the first of its kind to identify dominant periodicities in drought variability over the whole of Canada in terms of when the drought events occur, their duration, and how often they occur.
Highlights
Drought is a naturally occurring environmental phenomenon and a major natural hazard that can have devastating impacts on regional water resources, agriculture, industry, and other social-ecological systems, with far-reaching impacts in an increasingly globalized and uncertain world (IPCC, 2013; Sternberg, 2011)
Drought events are characterized by the Standardized Precipitation Evapotranspiration Index (SPEI; VicenteSerrano et al, 2010) over various temporal scales (1, 3, 6, and 12 consecutive months, 6 months from April to September, and 12 months from October to September)
The results further indicate that the Arctic Oscillation (AO) was in antiphase with SPEI6Apr−Sep PC1 and SPEI12Oct−SepPC2 during the study period from 1950 to 2013
Summary
Drought is a naturally occurring environmental phenomenon and a major natural hazard that can have devastating impacts on regional water resources, agriculture, industry, and other social-ecological systems, with far-reaching impacts in an increasingly globalized and uncertain world (IPCC, 2013; Sternberg, 2011). Still among the least understood extreme weather events affecting larger areas, droughts have proved to be the costliest and most widespread of natural disasters (Bryant, 2005; Wilhite, 2000b). This is primarily due to their usually lengthy duration, severity, and large spatial extent, sometimes reaching continental scales and lasting for many years (Sheffield et al, 2009). Droughts can affect all components of the hydrological cycle, from its origin as a deficit in precipitation (P ; Dai, 2011; Palmer, 1965; McKee et al, 1993), to its combination with high evapotranspiration losses that can lead to a deficit in soil moisture and subsequent manifestation into a hydrological drought (Tallaksen and Stahl, 2014).
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