Ocean chlorophyll concentrations. Satellite image showing the season-long composites of ocean chlorophyll concentrations from 21st June to 20th September 2012. Purple and blue represent lower chlorophyll concentrations, whilst oranges and reds represent higher chlorophyll concentrations. The differences in colour indicate areas with lesser or greater phytoplankton biomass. derived from visible radiometric measurements made by the Visible Infrared Imaging Radiometer Suite (VIIRS) sensor onboard the Suomi National Polar-orbiting Partnership (NPP) weather satellite.