Rossby Wave Analysis of Subsurface Temperature Fluctuations along the Honolulu-San Francisco Great Circle

Abstract

Seven years of XBT observations collected between Honolulu and San Francisco reveal subsurface temperature fluctuations with strong, in-phase vertical coherence and fair horizontal coherence over 1000 km distance. Their annual and semi-annual harmonics exhibit randomness of phase, suggesting that the fluctuations are modeled better as a stochastic process than as a deterministic signal. Cross-spectral fitting of a stochastic, first baroclinic mode Rossby wave model to the fluctuations demonstrates the Rossby waves could be producing 50?60% of the observed subsurface covariance at periods exceeding nine months. Phase is seen to propagate northwestward and energy westward and southwestward. The corresponding sea surface velocities and sea level fluctuations are of the order 1 cm s?1 and 1.5 cm.