EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Skillful seasonal prediction of North American summer hot days

Liwei Jia1,2, Tom Delworth1, Sarah Kapnick1, Xiaosong Yang1, Nathaniel Johnson1,3, William Cooke1, Feiyu Lu3, Matthew Harrison1, Anthony Rosati1,2, Fanrong Zeng1, Colleen McHugn1,4, Michell Bushuk1,2, Yongfei Zhang3, Andrew Witternberg1, Liping Zhang1,2, Hiroyuki Murakami1,2, and Kai-chi Tseng3
Liwei Jia et al.
  • 1Geophysical Fluid Dynamics Laboratory, Princeton, NJ
  • 2University Corporation for Atmospheric Research, Boulder, CO
  • 3The Program in Atmospheric and oceanic Sciences, Princeton University, Princeton, NJ
  • 4SAIC, Science Applications International Corporation, Reston, VA

This study shows that the frequency of North American summer hot days are skillfully predictable months in advance in the newly-developed GFDL (Geophysical Fluid Dynamics Laboratory) SPEAR (Seamless System for Prediction and EArth System Research) seasonal forecast system. We also demonstrate that climate change, the Pacific Decadal Oscillation (PDO), the Atlantic Multidecadal Oscillation (AMO) and atmosphere-land feedback all contribute to the seasonal predictive skill of the frequency of North American summer hot days. Using a statistical optimization method (Average Predictability Time) we identify two large-scale components of the frequency of North American summer hot days that are predictable with significant correlation skill. One component shows an increase in the frequency of summer hot days everywhere over North America and is highly predictable at least 9 months in advance. This component is related to a secular warming trend. Another predictable component shows largest loadings over the central U.S., and is significantly predictable 6 months ahead. This second component is related to the PDO and the AMO, and is significantly correlated with the central U.S. soil water. These findings have potential implications for predictions of North American summer hot days on seasonal time scales.

How to cite: Jia, L., Delworth, T., Kapnick, S., Yang, X., Johnson, N., Cooke, W., Lu, F., Harrison, M., Rosati, A., Zeng, F., McHugn, C., Bushuk, M., Zhang, Y., Witternberg, A., Zhang, L., Murakami, H., and Tseng, K.: Skillful seasonal prediction of North American summer hot days, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10100,, 2021.

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