Sea surface temperature anomalies in the northwestern Indian Ocean and its adjacent seas

180-187XBT, MBT and hydrographic data of 30 y are. used (i) to study regular formation of sea surface temperature anomalies (SSTA) and (ii) for their evaluation in the area extending from the equator to about 20-degrees-N and between 38-degrees and 60-degrees-E. This area includes the southern Red Sea, Gulf of Aden, Arabian Sea and northwestern Indian Ocean (NWIO). Annual sea surface temperature (SST) reveals 2 normal phases in the southern Red Sea-warming during spring and summer and cooling during autumn and winter. The other 3 areas exhibit 4 phases: (1) warming, (2) cooling, (3) warming and (4) cooling with some lags in period from one area to another. Time distribution of SSTA values displays both positive and negative cycles. The periods of these cycles fluctuate between 10 and 12 y. These cycles are associated with 11 y cycle of the sunspot activities. Normal SSTA band (-0.5-degrees to 0.5-degrees-C) occupies about 57% of the investigated period, while the positive and negative bands occupy 30% and 13% of it respectively. Active zones and periods are determined from the horizontal distribution of maximum positive, negative and amplitude of SSTA of the 30 y period for each 5-degrees grid. Area between 10-degrees-15-degrees-N and 50-degrees-55-degrees-E is considered to be the most active zone and spring and summer months (April-September) the most active period of the year. Negative anomalies are more effective due to interannual variability in the strength of upwelling and significant horizontal advection