Citation

Chu JE, Timmermann A, Lee JY. Sci. Adv. 2019; 5(8): eaaw9950.

Affiliation

Department of Climate System and Research Center for Climate Sciences, Pusan National University, Busan 46241, South Korea.

Copyright

(Copyright © 2019, American Association for the Advancement of Science)

DOI

10.1126/sciadv.aaw9950

PMID

31457097

PMCID

PMC6703861

Abstract

Annual tornado occurrences over North America display large interannual variability and a statistical linkage to sea surface temperature (SST) anomalies. However, the underlying physical mechanisms for this connection and its modulation in a rapidly varying seasonal environment still remain elusive. Using tornado data over the United States from 1954 to 2016 in combination with SST-forced atmospheric general circulation models, we show a robust dynamical linkage between global SST conditions in April, the emergence of the Pacific-North American teleconnection pattern (PNA), and the year-to-year tornado activity in the Southern Great Plains (SGP) region of the United States. Contrasting previous studies, we find that only in April SST-driven atmospheric circulation anomalies can effectively control the northward moisture-laden flow from the Gulf of Mexico, boosting low-level moisture flux convergence over the SGP. These strong large-scale connections are absent in other months because of the strong seasonality of the PNA and background moisture conditions.

Language: en