A diagnostic study of the velocity structure of a meandering jet using a primitive equation model with dynamic mode initialization

Abstract

A high resolution, 20-level, primitive equation (PE) model of the California coastal region is initialized using temperature data acquired during the first California Transition Zone (CTZ) cruise from 6 to 12 July 1988 for the purpose of diagnosing the three-dimensional dynamically balanced flow field for the region. The major feature in the region during the cruise period was a strong meandering jet which flowed equatorward and offshore, oriented in a northeast to southwest direction. The quality of data acquired during cruise CTZR1 is sufficiently high to enable diagnosis of the horizontal (baroclinic) and vertical velocity field using the numerical model. The measured (ADCP) currents showed more details of the flow at deeper depths than the model, which showed a broader baroclinic flow at depth and a level of no motion near 300 m. The maximum surface velocities from model and ADCP cross-sections agreed to within 10 cm/sec except for leg G, in which ADCP velocity was greater than the model velocity by about 30 cm/sec. The sign of vertical velocity agrees very well with independent estimates made from bio-optical data; however, the magnitude calculated by the model is 30 to 60 times larger than that estimated from the bio-optical observations.