Spatiotemporal changes of drought characteristics and their dynamic drivers in Canada

Abstract

Abstract There has been a growing concern regarding impacts of global warming on droughts, which can have devastating effects on the environment, society, and economy of nations worldwide. Drought characteristics in terms of duration, frequency, area, and severity are investigated using the Standardized Precipitation Evapotranspiration Index (SPEI) at seasonal (3-month) and annual (12-month) time scales for Canada over 1950–2016 derived from the Climatic Research Unit (CRU) TS4.03 gridded data. Using k-means clustering, Canada is divided into four sub-regions, each with distinct drought characteristics. Next, the influence of climate drivers such as the El Nino-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on regional drought variability were examined using a Bayesian Dynamic Linear (BDL) model. The results show that between 1950 and 2016 (1) there has been a prevalent drying trend in southwestern Canada during winter; (2) changes in maximum drought durations have occurred with dipolar patterns, i.e., northern Canada has experienced a longer drought duration than southern Canada; (3) drought frequency, area, and severity have predominantly shown statistically significant decreasing trends, indicating that droughts in Canada have generally become less severe; and (4) the relationships between climate anomalies and drought variability have changed over time. Droughts are generally more negatively correlated to ENSO and PDO after 1970s, but more positively correlated to the Atlantic Multi-decadal Oscillation (AMO) and Arctic Oscillation (AO) after the 1980s. The results provide a better understanding of the characteristics of meteorological droughts in Canada, essential for improving the risk management and mitigation strategies on the impact of droughts.