Annual Baroclinic Rossby Waves in the Central North Pacific

Abstract

We analyze XBT data, collected in the central North Pacific under the NORPAX program (TRANSPAC), by means of inverse methods (cross-spectral fit). We separate the data into two parts: a fluctuation with length scales in the order of the dimensions of the North Pacific basin and a wavelike fluctuation with much shorter scales of a few hundred kilometers. At the annual frequency we find the wavelike fluctuation to consist of a random field of first-order baroclinic Rossby waves traveling basically northwest with wavelengths of ?300 km and phase speeds of ?1 cm s?1. The group velocity is directed mainly southwest and is of the order of 1 cm s?1. We describe the fields of temperature, pressure, velocity, sea level elevation, and horizontal and vertical particle displacement associated with the annual baroclinic Rossby waves.