World drought frequency, duration, and severity for 1951-2010

TLDR

Climate change, with rising temperatures and more extreme precipitation, makes drought a key natural disaster. The study maps global drought frequency, duration, and severity for 1951–1970, 1971–1990, and 1991–2010 to identify drought hotspots. Drought metrics were derived from monthly SPI‑12 values calculated with a Gamma‑fitted 60‑year baseline, using 0.5° × 0.5° GPCC precipitation grids. The analysis identifies shifting drought hotspots—Central US and Argentina in 1951–1970, Southern Chile and the Sahel in 1971–1990, and the Amazon and Congo in 1991–2010—and shows a modest global rise in drought components, with significant increases in Africa, Eastern Asia, the Mediterranean, and Southern Australia, but declines in the Americas and Russia.

Abstract

In the context of climate change characterized by rising temperature and more extreme precipitation regimes, drought is one of the most relevant natural disasters. This paper presents maps of global drought frequency, duration, and severity for the periods 1951–1970, 1971–1990, and 1991–2010, to give an overview of the respective drought hot spots. Drought frequency is defined as the number of drought events occurred, drought duration as the number of months in drought conditions, and drought severity as the sum of the integral area below zero of each event. Because drought is mainly driven by rainfall deficits, we chose the Standardized Precipitation Index (SPI) as the base indicator to derive drought-related quantities. SPI-12 has been calculated on a monthly basis using a Gamma distribution fitted to a 60-year baseline period (1951–2010). Global grids (0.5° × 0.5°) of the Full Data Reanalysis Version 6.0 dataset provided by the Global Precipitation Climatology Centre (GPCC) have been used as precipitation data input. The regions most exposed to prolonged and severe droughts during 1951–1970 were the Central United States, the Argentinian Pampas, Russia, and Central Australia; during 1971–1990 they were Southern Chile, the Sahel, and Siberia; during 1991–2010 they were the Amazon Forest, the Congo River Basin, Mongolia, North Eastern China, and Borneo. A linear trend analysis between 1951 and 2010 shows a small global increase in each drought component, but drought frequency decreased in the Northern Hemisphere. The increase in drought frequency, duration, and severity is found to be significant in Africa, Eastern Asia, Mediterranean region, and Southern Australia, while the Americas and Russia show a decrease in each drought component.