Increase in Compound Drought and Heatwaves in a Warming World

• Published in: Geophysical research letters 2021-01, Vol.48 (1), p.n/a
• Main Authors: Mukherjee, Sourav, Mishra, Ashok Kumar
• Format: Article
• Language: English
• Subjects: compound extremes; drought; heatwave
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL090617

Compound drought and heatwaves can cause significant damage to the environment, economy, and society. In this study, we quantify the spatio‐temporal changes in compound drought and heatwave (CDHW) events by integrating weekly self‐calibrated Palmer Drought Severity Index (sc_PDSI) and daily maximum temperatures during the period 1983 to 2016. Multiple data products are used to examine the robustness of sc_PDSI in the compound event analysis. The results consistently suggest significant increases in drought‐related heatwaves and affected global land area in recent (warmer) periods. Several regions across the globe witnessed rise in CDHW frequency (one to three events/year), duration (2–10 days/year), and severity. This increasing pattern is spatially asymmetric, and greater amplification is observed across the Northern hemisphere due to recent warming. Furthermore, the background aridity influences the spatiotemporal evolution of CDHW events. The results can be applied to minimize the impacts of extreme CDHWs in critical geographical regions. Plain Language Summary The increase in global temperature has altered the spatio‐temporal pattern of individual extreme events (e.g., drought and heatwave). However, a limited number of studies investigated their compound characteristics in terms of duration, frequency, severity, and spatial extent. This study explores the spatio‐temporal changes in compound events that have a significant impact on health, agriculture, economy, and environment around the globe. The compound framework has a key advantage that it can capture the weekly droughts and heatwaves at daily time scale. The results can directly map the critical regions and reveal the dependence between two extreme events (i.e., drought and heatwaves). This study also examines the spatial asymmetry across the globe and the influence of background aridity on compound extremes in a warming climate. This analysis can be extended to inform stakeholders where the coevolution of these extreme events is likely to be higher under climate change. The results of this analysis will aid forecasting efforts and help to improve hazard preparedness and mitigation strategies for the vulnerable regions of the globe. Key Points A significant increase in drought‐related heatwave events and corresponding spatial extent is observed in the recent period The frequency, duration, and severity of compound drought and heatwave events have increased in five out of six continents The increa