The Role of Neutral Singular Vectors in Midlatitude Air–Sea Coupling

Abstract

Abstract The role of “neutral vectors” in midlatitude air–sea interaction is studied in a simple coupled model. Neutral vectors—the right singular vectors of the linearized atmospheric model tendency matrix with the smallest singular values—are shown to act as pattern-specific amplifiers of ocean SST anomalies and dominate coupled behavior. These ideas are developed in the framework of a previously developed analytical coupled model, which described the mutual interaction across the sea surface of atmospheric and oceanic Rossby waves. A numerical model with the same physics is developed that permits the consideration of nontrivial background conditions. It is shown that the atmospheric modes that are least damped, and thus the patterns most easily energized by stochastic forcing, are neutral vectors.