Abstract
Previous studies indicate that cold filaments off northern California have sharp southern (s-type) and diffuse northern (d-type) thermal boundaries. In this study, 44 AVHRR satellite images taken from three coastal regions in the California Current System (northern, central, and Baja California) over a period of 10 years were used to examine the regional variation in surface frontal structure associated with cold filaments. The images were specifically chose from months where past mean wind conditions indicated upwelling occurred because cold filaments appear to be more abundant during the upwelling season. The images also were chosen to provide independent realizations of filament structure. Distributions of average gradient magnitude as a function of gradient angle were used to provide a more compact representation of the frontal information contained in each image. An analysis of these distributions shows that the sharp / diffuse boundary structure associated with cold filaments observed in shipboard data dominates the total surface frontal structure found in satellite data for two of the three regions studied. The recurrent, ubiquitous patterns found in the satellite-determined frontal structure are discussed in terms of their potential effects on acoustic propagation and regional implications on ecological community structure in the California Current System.
Highlights
Filaments can transport cold coastal water to distances as far as several hundred kilometers offshore into the California Current
The purpose of this study is to further quantify temperature frontal patterns found in regions of recurrent, cold filaments by using Advanced Very High Resolution Radiometer (AVHRR) imagery taken during the last 10 years off the west coast of North America
For all panels in these figures, clouds, land, and data not in the grid are masked in black; coastlines are shown with dotted white lines
Summary
The northern boundaries, hereinafter called d-type boundaries (for diffuse transition), usually exhibit a smoother, more diffuse transition in SST from the warm water north of the filament into the filament's center. Both density compensated (e.g., Flament et al, 1985; Kosro and Huyer, 1986; Rienecker and Mooers, 1989) and non-density compensated (e.g., Kosro and Huyer, 1986; Reinecker et al, 1985; Ramp et al, 1991) s-type boundaries have been observed
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