Impact of dependence changes on the likelihood of hot extremes under drought conditions in the United States

The conditional dependence between droughts and hot extremes in many regions tends to lead to compound dry and hot extremes that may cause serious impacts on the ecosystem, human society and infrastructure. Thus, it is of particular importance to understand variations of the conditional dependence between droughts and hot extremes under global warming. We investigated changes in the dependence between droughts (characterized by the Standardized Precipitation Index, SPI) and hot extremes (characterized by extreme temperature) during summer for two periods 1949–1979 and 1980–2010 in the United States. The copula method was employed to construct the conditional distribution of hot extremes under drought conditions to show changed likelihoods of hot extremes. Results demonstrated increased negative dependence between droughts and hot extremes in large regions in the western, southern and northeastern U.S., leading to a higher likelihood of hot extremes conditional on droughts from the first period 1949–1979 to the recent period 1980–2010. Meanwhile, decreased negative dependence between droughts and hot extremes was shown in parts of Midwest and southeastern U.S., leading to a decreased likelihood of hot extremes conditional on droughts. Due to disastrous impacts of both droughts and hot extremes, our findings will aid mitigation efforts of extremes in the U.S. in a warmer climate.

Duke Scholars

Author Wenhong Li Earth and Climate Sciences