Chlorophyll distribution pattern in the Arabian Sea: seasonal and regional variability, as observed from SeaWiFS data

The SeaWiFS data for the period 1997-1998 and 1998-1999 have been used to understand the variability of chlorophyll on an intra-annual and an inter-annual basis. Satellite-derived chlorophyll data composited for an 8-day period provide the ability to describe changes in oceanic waters. It is well known that such changes otherwise are difficult to monitor during in situ observations alone, due to undersampling of large temporal and spatial variability. In order to assess the satellite-derived chlorophyll, a limited comparison was made with the cruise data for the Arabian Sea for different seasons and representative locations. This comparison was restricted to the cloud-free period of the year (October to April). The chlorophyll concentration values and the overall distribution pattern was found to match reasonably well. A total of nine locations were selected, two near coast to near coast-offshore, four open ocean and three offshore waters. The range of chlorophyll concentration varied from as low as 0.06 mg m(-3) to as high as 5.5 mg m -3 . Variability is seen more in near-coast location. The highest concentrations were observed at almost all locations during the January-February period. Features are stable during certain periods of the year while at specific periods, very fast changes are observed. Seasonal periodicity is evident in inter-annual analysis. The study shows the potential of satellite-derived information for understanding the seasonal and inter-annual variability in chlorophyll.