A Simple Model of the Atmospheric Response to ENSO Sea Surface Temperature Anomalies

R. Kleeman Bureau of Meteorology Research Centre, Melbourne, Victoria, Australia

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Abstract

A low-order tropical atmospheric model is developed that gives a reasonable account of the tropical precipitation and circulation anomalies observed during various El Niño and La Niña events. The dynamical part of the model is a linearization about a state of rest with the usual tropical vertical mode retained. The heating is obtained from latent and nonlatent sources with the former obtained from perturbing a steady-state moisture equation about climatology and confining the heating to high SST regions. A thorough sensitivity analysis is undertaken and the model tendency to place major anomalies on the western and northern side of SST anomalies is examined.

Abstract

A low-order tropical atmospheric model is developed that gives a reasonable account of the tropical precipitation and circulation anomalies observed during various El Niño and La Niña events. The dynamical part of the model is a linearization about a state of rest with the usual tropical vertical mode retained. The heating is obtained from latent and nonlatent sources with the former obtained from perturbing a steady-state moisture equation about climatology and confining the heating to high SST regions. A thorough sensitivity analysis is undertaken and the model tendency to place major anomalies on the western and northern side of SST anomalies is examined.

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