The authors kindly acknowledge I. Durre, R. Vose, M. Squires, X. Yin, J. Nielsen-Gammon, J. Christy, and J. Curtis for providing feedback on this approach. We also thank three anonymous reviewers for providing actionable feedback that helped strengthen the manuscript.
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The term “annual cycle” is often used to refer to a single cosine, sine, or harmonic even though the annual march of temperatures for some locations can be highly asymmetric. Here, we refer to an annual cycle as the annual march of temperatures whose morphology can vary from station to station.