Impacts of the North Atlantic subtropical high on interannual variation of summertime heat stress over the conterminous United States

  • Wenhong LiEmail author
  • Tian Zou
  • Laifang Li
  • Yi Deng
  • Victor T. Sun
  • Qinghong Zhang
  • J. Bradley Layton
  • Soko Setoguchi


Heat index (HI) provides a proven indicator of heat stress and discomfort for the general public. The index takes the integrated effects of both temperature and humidity into account, and both factors are regulated by large-scale circulation patterns. This study examines the impacts of the North Atlantic Subtropical High (NASH) on HI over the conterminous United States (CONUS). The analysis suggests that the HI is primarily controlled by surface air temperature over the CONUS; but is negatively correlated with relative humidity in the western and Central US north of 40°N. In addition, winds contribute to the variation of HI in the Midwest and the southeastern US. By regulating these meteorological parameters, the movement of the NASH western ridge significantly impacts HI over the US, especially the Southeast. When the NASH western ridge is located northwest (NW) of its climatological mean position, abnormally high temperatures are observed due to fewer clouds and a precipitation deficit, leading to positive HI anomalies over the southeastern US. In contrast, when the western ridge is located in the southwest (SW), temperature decreases and HI anomaly becomes negative over the Southeast, even though relative humidity increases east of 100°W. NASH has a weaker impact on the HI when it is far from the North American continent, especially during southeast (SE) ridge years. In the future, CMIP5 models project an increase in HI over the entire CONUS, while NASH-induced HI will be weakened during the NW, SE and NE ridge years but strengthened when its ridge moves to the SW quadrant. These results suggest that future increases in heat stress are likely caused by climatological warming and NASH intensification.


US heat waves Heat index North Atlantic subtropical high NASH western ridges 



We thank the international modeling groups for providing their data for analysis, the Program for Climate Model Diagnosis and Intercomparison (PCMDI) for collecting and archiving the model data, the JSC/CLIVAR Working Group on Coupled Modeling (WGCM) and their Coupled Model Intercomparison Project (CMIP) and Climate Simulation Panel for organizing the model data analysis activity, and the IPCC WG1 TSU for technical support. The IPCC Data Archive at Lawrence Livermore National Laboratory is supported by the Office of Science, US Department of Energy. This work is supported by the NIH Grant NIH-1R21AG044294-01A1. L Li is supported by the NSF PREEVENTS (grant number: NSF-ICER-1663138). 

Supplementary material

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Earth and Ocean Sciences, Nicholas School of the EnvironmentDuke UniversityDurhamUSA
  2. 2.Department of Atmospheric and Oceanic Sciences, School of PhysicsPeking UniversityBeijingChina
  3. 3.School of Earth and Atmospheric SciencesGeorgia Institute of TechnologyAtlantaUSA
  4. 4.John Dewey AcademyGreat BarringtonUSA
  5. 5.RTI Health SolutionsResearch Triangle ParkUSA
  6. 6.Institute for Health, Health Care Policy and Aging ResearchRutgers Biomedical and Health SciencesNew BrunswickUSA

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