资源环境科技发展态势分析平台

The Intergovernmental Panel on Climate Change (IPCC) reports that the changes in extreme events are expected to be detected earlier than changes in climate averages. Hot temperature extremes in the United States cause important economical, societal, and environmental impacts. Thus, the climatology of hot extremes and heat waves (HWs) merits further examination. Spatiotemporal trends of five extreme temperature indicators were investigated for the period 1948-2017 for the Mississippi River Basin (MRB), which covers approximately 41% of the Contiguous United States. A hot extreme was identified using the 90th percentile threshold and a HW was defined as two or more consecutive hot temperature extreme days. Results suggest that the western, northwestern, southern, and northern parts of the MRB are regions with a growing risk of extreme temperatures with more frequent and longer hot events. Change in the eastern part of the MRB suggests a smaller risk with a general downward trend in HWs.

Change-point analysis indicates that these climatic data exhibit nonstationarity. A significant increase happened starting in 1994 in the percentage of area with a HW longer than 10 consecutive days. Frequency and length of HWs were greater during El Nino years. However, this finding is not statistically significant. An increase in HW duration and frequency can impact water availability, human and animal health, agriculture and the economy. Results from this study assist in finding hotspots where changing extreme conditions have happened and where society may need to make adjustments related to water use, human outdoor activities and agricultural practices.