The California Current — 



A Comparison of False- Color CZCS Pigment 



and Thermal Infrared Imagery 



July 1981 



The CZCS image (27-1) and AVHRR image (27-2) were obtained on 

 7 July and 8 July, respectively. These images of the West Coast were made 

 during the presence of an unusually strong high pressure center in the 

 Pacific Northwest coupled with a low pressure center off the coast of 

 southern California. The result was strong northerly winds along the coast 

 with sustained speeds of 15 m s"' near Cape Mendocino. 



The images reveal several features typical of eastern boundary currents. 

 Such currents are typically areas of high productivity and, hence, high 

 biomass. They are also areas of upwelling, although there is some question 

 as to whether this is classic wind-driven coastal upwelling or a larger scale 

 process forced by the curl of the wind stress. 



The near-time coincidence of these images reveals significant large-scale 

 similarities between near-surface pigment (27-1) and sea surface 

 temperature distributions (27-2). In general, colder water is associated 

 with higher pigment concentrations, although one can detect numerous 

 areas that differ from this. For example, a comparison of the two images 

 indicates that the upwelling areas near Cape Mendocino have very low 

 temperatures and low pigment concentrations. This is consistent with the 

 combination of upwelling of very deep, clear water to the surface and the 

 delay time in the phytoplankton response to this nutrient-rich water. 



Finally, the CZCS pigment image (27-1) shows some of the limitations 

 of the current CZCS algorithms. In particular, some of the high pigment 

 concentrations near San Francisco Bay and near the mouth of the 

 Columbia River are a result of high sediment concentrations, not 

 phytoplankton concentrations. 



26 



