A COMPARISON OF SHIP AND SATELLITE CHLOROPHYLL FROM CALIFORNIA AND PERU

Ship surface chlorophyll measurements from coastal California and Peru have been processed for comparison with surface chlorophyll estimated during the lifetime of the coastal zone color scanner (CZCS). The shi p data shows that chlorophyll concentrations are higher off Peru than California, consistent with the Peru Current system's being more produ ctive. Off California the ship and satellite measurements yield simila r estimates of chlorophyll concentration (the average ratio of ship to satellite is 1.1), but off Peru the satellite yields substantially lo wer concentrations (average ratio of 3.8). The lower satellite values off Peru are likely due to sparse satellite coverage and/or problems w ith atmospheric corrections. For California, the inshore (0-100 km) sh ip and satellite chlorophyll estimates are similar, but offshore (200- 250 km) the satellite yields higher values. Both estimates, however, c onfirm the presence of a winter chlorophyll maximum in offshore Califo rnia waters (likely due to increased nutrient concentrations), increas es in chlorophyll per cell, and mixing of subsurface chlorophyll maxim um to the surface. Conversely, off Peru, offshore ship and satellite v alues are in closer agreement than inshore values. As a result onshore -offshore gradients are weaker in the satellite data for both Californ ia and Peru. The gradient problem is likely the result of the satellit e algorithm. Different algorithms may be needed for coastal waters, do minated by relatively large and colonial phytoplankton, and open ocean waters, dominated by small solitary phytoplankton.