A multi-index evaluation of changes in compound dry and hot events of global maize areas

Abstract

The nonexistence of universal drought indicators may lead to uncertainties in the variability of drought, leading to discrepancies in the frequency change in compound dry and hot events (CDHEs) in different regions across the globe. Understanding the impact of the selection of drought indicators on the variability of CDHEs is important for assessing their risks and pursuing mitigation measures. However, quantitative assessments of differences in CDHEs variabilities based on different drought indicators have been lacking. In this study, we evaluate changes in CDHEs based on three different drought indices, including self-calibrating Palmer Drought Severity Index (scPDSI), Standardized Precipitation Index (SPI), and Standardized Precipitation-Evapotranspiration Index (SPEI), and Standardized Temperature Index (STI) as the hot indicator over global maize-producing areas. Generally, the compound dry and hot event defined by SPEI & STI shows a relatively higher magnitude of increase in the frequency and spatial extent compared with that defined by SPI & STI and scPDSI & STI from 1949–1980 to 1981–2012 over most regions. For the top ten maize-producing countries, the frequency of different countries affected by CDHEs at the same time also increases from 1949–1980 to 1981–2012 for these three types of compound events. Consistent patterns are shown based on different thresholds and different base periods in defining compound events. Results from this study could help understand compound event variations and provide useful insights for agricultural management under global warming.