A critical examination of a newly proposed interhemispheric teleconnection to Southwestern US winter precipitation

June 23, 2019

Peter Gibson and Duane Waliser (NASA JPL/CalTech), along with CW3E scientist Mike DeFlorio, recently published a reply in Nature Communications to a research article investigating interhemispheric drivers of subseasonal-to-seasonal (S2S) predictability of southwestern U.S. precipitation.

The purpose of the reply was to test the robustness of the claim that New Zealand SST anomalies play an important role in altering atmospheric circulation in the North Pacific that subsequently influences southwestern U.S. winter precipitation variability. Gibson et al. (2019) focused on additional testing of the lagged correlation strength between SST anomalies in key regions proposed in the original article. Gibson et al. (2019) found that non-stationarity, memory, and shared variability with other well-known modes of internal variability make a large contribution to the reported correlation strength between these regions of interest. Using large model simulations with multiple initial conditions, it was shown that similar associations between these regions can often arise by chance alone. The proposed mechanism, whereby SST anomalies near New Zealand enhance remote adiabatic warming and reduce cloud cover, was also called into question from the perspective of other satellite and reanalysis datasets.

Uncovering new physical mechanisms that may lead to increased S2S prediction skill of western U.S. precipitation is a challenging and fundamental task that the partnership between CW3E and JPL continues to undertake. This is an important issue for our stakeholders at the California Department of Water Resources, and more generally for water resource managers across the southwestern and western United States.

Gibson, P. B., D. E. Waliser, and M. J. DeFlorio (2019), A critical examination of a newly proposed interhemispheric teleconnection to Southwestern US winter precipitation. Nature Communications, 10, 2687. https://doi.org/10.1038/s41467-019-10528-y.

Original article:

Mamalakis, A., J. Y. Yu, J. T. Randerson, A. AghaKouchak, & E. Foufoula-Georgiou (2018). A new interhemispheric teleconnection increases predictability of winter precipitation in southwestern US. Nature Communications, 9(1), 2332. https://doi.org/10.1038/s41467-018-04722-7.