SEAWIFS OBSERVATION OF CHLOROPHYLL DISTRIBUTION IN REGIONAL SEAS

The Centre for Remote Imaging, Sensing and Processing (CRISP) has been receiving SeaWiFS data since September 1999. To date, we have acquired more than 1200 passes covering regional seas in and around Southeast Asea. The data are processed into Level 1 and Level 2 format using the SeaDAS software provided by NASA and georectified using the software developed at CRISP. Cloud free multi-day composite maps of the chlorophyll-a concentration distribution at 1 km resolution are generated for regional seas. Short-term changes in chlorophyll concentration may indicate the occurrence of p henomena like red tides and pollution which have significant environmental and economic effects. In this context, we discuss the abrupt and abnormal changes of the pattern of chlorophyll concentration observed in Kimanis Bay, Sabah as well as Daya Bay, near Hong Kong during reported red tide periods. The behaviors of normalized water leaving radiances in the suspected region are also discussed. In the reported red tide areas, the chlorophyll-a concentrations and normalized water leaving radiances during reported tide periods are considerably different from other days. Thus, the change of chlorophyll -a concentration and spectrum of the normalized water leaving radiance may be used as indications of red tide.