Journal article

How Wet and Dry Spells Evolve across the Conterminous United States Based on 555 Years of Paleoclimate Data

Michelle Ho, Upmanu Lall, Edward R Cook



Evolving patterns of droughts and wet spells in the conterminous United States (CONUS) are examined over 555 years using a tree-ring-based paleoclimate reconstruction of the modified Palmer drought severity index (PDSI). A hidden Markov model is used as an unsupervised method of classifying climate states and quantifying the temporal evolution from one state to another. Modeling temporal variability in spatial patterns of drought and wet spells provides the ability to objectively assess and simulate historical persistence and recurrence of similar patterns. The Viterbi algorithm reveals the probable sequence of states through time, enabling an examination of temporal and spatial features and..

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University of Melbourne Researchers


Awarded by NSF

Awarded by Directorate For Geosciences

Funding Acknowledgements

We wish to thank David Farnham, Soojun Kim, Ipsita Kumar, Indrani Pal, and Xun Sun for their helpful discussions. We would also like to thank the Editor in Chief, Timothy DelSole, and three anonymous reviewers for providing guidance and informative feedback and suggestions. This work is funded by NSF Awards 1360446 and 1404188. Lamont-Doherty Contribution Number 8227. Support for the Twentieth Century Reanalysis Project version 2c dataset is provided by the U.S. Department of Energy, Office of Science Biological and Environmental Research, and by the National Oceanic and Atmospheric Administration Climate Program Office.