Pigment patterns in the Arabian Sea: Spatio-temporal variability as observed by ADEOS

Abstract

The spatial and temporal variations of the near-surface concentration of phytoplankton pigment observed by ADEOS during November 1996 - May 1997 are studied in relation to SST and winds. Monthly composite images from OCTS depict spatial and temporal variation of phytoplankton pigment concentration in the Arabian Sea. Appreciable regional differences in levels and timing of changes of pigment concentration was found, with a large bloom north of 20 degrees N in February 1997. Pigment concentration at 20 degrees N, 10 degrees N and equator ranged from 0.3-3.0, 0.01-0.3 and 0.01-1.0 mg m super(-3) respectively during the NEM (October-January) period and between 0.01-0.3, 0.01-0.3 and 0.01-0.03 mg m super(-3) respectively during the TR (February-May) period. Monthly means of SST and winds are related to monthly averaged pigment concentrations in order to explain the observed changes in pigment concentration. Low SST and high pigment concentration in the northern Arabian Sea during northeast monsoon may be due to the winter cooling as reported earlier. Chlorophyll concentrations remained relatively high from November to February when winds reversed direction. The results indicate that the OCTS images along with the wind field obtained from NSCAT are useful for understanding the distribution of pigment concentration in the Arabian Sea.