The Impact of Low-Latitude Anomalous Forcing on Local and Remote Circulation: Winters 1978/79–1986/87

Abstract

Abstract The impact of anomalous tropical forcing on the anomalous tropical and extratropical circulation is examined by comparing the response of a global steady state linear primitive equation model with observations for nine (1978/79–1986/87) December–January–February (DJF) seasons. Outgoing longwave radiation (OLR) anomalies are used as proxies for tropical latent heat release. Root mean square amplitude and anomaly pattern correlation (APC) are chosen to be the verification tools. It is shown that with OLR as the only forcing, the linear model produces a fairly realistic level of tropical interannual variability in the wind (both rotational and divergent) and geopotential height fields. The nine DJF's mean skill score, as measured by APC, is highest in the tropics for u, v and Φ between 600 to 900 mb where the moan APC is 0.5–0.6. There is skill in the simulation of both the rotational and divergent components of the circulation. In fact, the APC for the velocity potential at upper levels over the gl...