Spatial reorganization of SST anomalies by stationary atmospheric waves

The dynamics of sea surface temperature (SST) anomalies that force stationa ry atmospheric waves, which in turn, feed back on the SST held is addressed . The phenomena is isolated by analyzing the dynamics of a slab ocean that is thermally coupled to an atmospheric model. Particular emphasis is put on identifying SST structures that are weakly damped by the joint effect of a ir-sea heat transfer and atmospheric wave dynamics. A frame work is presented that singles out long-lived SST features in a sla b ocean coupled to an arbitrary linear atmospheric model. It is demonstrate d that an SST anomaly eventually disintegrates into a number of propagating wave packets. The wave packets are confined in a Gaussian envelope, and ea ch packet is tied to a stationary wave of a particular wavelength. These st ructures are a manifestation of coupled SST-atmosphere mode, for which the atmosphere and the ocean nearly are in thermal equilibrium. However, a smal l disequilibrium causes the wave packet to propagate and to broaden in an a pparent diffusive manner. Central ideas pertaining to the mid-latitude SST dynamics are illustrated b y analyzing the thermal feedback between a two-level atmospheric model (on a beta -plane) and a dynamically passive slab ocean. The relevance of the p resent idealized coupled-modes to the SST variability in the mid-latitudes and in atmospheric GCMs coupled to slab oceans is discussed. (C) 2001 Elsev ier Science B.V. All rights reserved.