Mapping Large-scale Climate Variability to Hydrological Extremes: An Application of the Linear Inverse Model to Subseasonal Prediction

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Journal Article

The excitation of the Pacific-North American (PNA) teleconnection pattern by the Madden-Julian Oscillation (MJO) has been considered as one of the most important predictability sources on subseasonal timescales over the extratropical Pacific and North America. However, until recently, the interactions between tropical heating and other extratropical modes and their relationships to subseasonal prediction have received comparatively little attention. In this study, a linear inverse model (LIM) is applied to examine the tropical-extratropical interactions. The LIM provides a means of calculating the response of a dynamical system to a small forcing by constructing a linear operator from the observed covariability statistics of the system. Given the linear assumptions, it is shown that the PNA is one of a few leading modes over the extratropical Pacific that can be strongly driven by tropical convection while other extratropical modes present at most a weak interaction with tropical convection. In the second part of this study, a two-step linear regression is introduced which leverages a LIM and large-scale climate variability to the prediction of hydrological extremes (e.g. atmospheric rivers) on subseasonal timescales. Consistent with the findings of the first part, most of the predictable signals on subseasonal timescales are determined by the dynamics of MJO-PNA teleconnection while other extratropical modes are important only at the shortest forecast leads.

Journal of Climate
Date Published
June 2021
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