Physical Oceanography, Vol.
ANALYSIS OF OBSERVATIONS AND METHODS FOR CALCULATING
HYDROPHYSICAL FIELDS IN THE OCEAN
SEASONAL VARIABILITY OF THE CALIFORNIA UNDERCURRENT:
STATISTICAL ANALYSIS BASED ON THE TRAJECTORIES OF
FLOATS WITH NEUTRAL BUOYANCY
C. A. Collins,
L. M. Ivanov,
and O. V. Mel’nichenko
The seasonal variation of the kinetic energy of the California Undercurrent and the eddy field in
the region of this current are reconstructed by analyzing the trajectories of floats with neutral
buoyancy (RAFOS) launched by the researchers of the Naval Postgraduate School (Monterey,
California, USA) for
(since 1992). These data are processed by using a mathematical ap-
proach based on the combination of a procedure of averaging over cells and a special filtration
approach with an aim to improve the statistical reliability of numerical calculations. The analysis
of the accumulated data shows that the kinetic energy of the California Undercurrent has a well
pronounced seasonal variation with two extrema in late spring and early autumn. The intensifi-
cation of the California Undercurrent in autumn is accompanied by a decrease in its extension in
the direction transverse to the coast. The eddy field of the California Undercurrent is especially
intense in autumn. At depths of
the annual average kinetic energy of the eddy field
increases with the distance from the coast up to about
127°W. Moreover, in this case, the zonal
anisotropy of the eddy field increases.
The California Current (CC) is a fragment of the general large-scale anticyclonic circulation in the north
part of the Pacific Ocean. Together with two undercurrents (the Coastal Current and the California Undercur-
rent), it forms the California circulation system, which is actually one of the most well-studied systems of cur-
rents in the World Ocean . Except a narrow coastal zone
the CC is a wide (up to
but, at the same time, weak (less than
surface flow penetrating only down to a depth of
and transporting cold and freshened subarctic waters to the equator for the whole year.
The Coastal Current is observed, as a rule, occasionally (in autumn and winter) over the shelf and continen-
tal slope. It transports water masses coming with the CC . To the north of
this countercurrent is often
called the Davidson Current.
The California Undercurrent (CUC) manifests itself as the maximum of velocity attained in the
m-layer below the ocean surface and transports warm and salty equatorial waters to the north along the continen-
tal slope. Although the CUC is, generally speaking, not intense and its average seasonal velocities are not higher
the velocities observed in the meandering midstream of this current whose width does not
can be much higher (up to
. Inside the
the CUC transports up
Naval Postgraduate School, Monterey, California, USA.
Marine Hydrophysical Institute, Ukrainian Academy of Sciences, Sevastopol.
Translated from Morskoi Gidrofizicheskii Zhurnal, No.
9–22, May–June, 2003. Original article submitted March 11, 2002.
0928-5105/03/1303–0135 $25.00 © 2003 Plenum Publishing Corporation 135