A study implementing Nonlinear Autoregressive with Exogenous Input (NARX) neural network has been undertaken to predict monthly and seasonal SST anomalies in the western Indian Ocean. The study involves a coastal site located along the eastern African seashore, and an oceanic site that lies precisely within the western pole of the Indian Ocean Dipole. Performance of the network is measured by a series of statistical indicators during testing phase , and results are compared with outputs from three other neural networks and a linear system, the Autoregressive Integrated Moving Average with Exogenous Input (ARIMAX) model. The NARX network has provided the best overall performance, but the other four models have also given sufficiently good predictions. The monthly predictions are on average within an error of ±0.09 o C for the first 50% and 90% within ±0.22 o C. The corresponding errors for the seasonal predictions are ±0.04 o C and ±0.09 o C, respectively. The RMSE between observations and predictions is about 0.13 o C and 0.06 o C for the monthly and seasonal SST anomalies, while the average correlation coefficient is about 0.88 and 0.98, respectively.

A numerical modeling study was carried out using the Regional Ocean Modeling System (ROMS) for the Tanzanian coast to investigate the seasonal dynamics of water circulation, temperature and salinity. The model results indicated the presence of an eddy on the surface that develops during the Northeast (NE) monsoon and which has not been documented previously. The study also revealed that, the core of the East African Coastal Current (EACC) passes adjacent to the coast, just off the three major islands of Pemba, Zanzibar, and Mafia. There are localized patches of strong currents parallel and adjacent to the mainland coast, with magnitudes that are influenced by the coastline configuration, bottom topography and the extent of exposure to the main stream of the EACC. The current speeds along the coast of Tanzania are lowest in February and March, and highest in July, August, and November but generally not exceeding 1 ms -1 . Surface salinities generally vary between 34.8 and 35.5, whereas surface temperatures range from a minimum of 25.0°C to a maximum of 30.2°C. The modelled salinity and temperature profiles are similar to those observed from field observations of previous investigations.

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Ocean circulation, upwelling phenomena and chlorophyll-a concentrations were investigated within the framework of numerical model simulations with 1/12° nested horizontal grid-size, in the tropical western Indian Ocean, along the coasts of Tanzania and Kenya. Ekman driven upwelling exhibited high levels of spatial and temporal variability in the region, characterized by a more vigorous occurrence/intensification during the Northeast than the Southwest Monsoon season. A similar trend was observed for chlorophyll-a distribution, but with an additional strong contribution during the inter-monsoon period from March to April. Trend analysis of a SST-derived coastal upwelling index (CUI) computed over the Pemba Channel and offshore of the East African Coastal Current (EACC), for 24 years (1990 - 2013), revealed a general linear relation of the form CUI(yr) = 2.4x10-7yr – 285, with a steady small annual increase of the upwelling phenomena by 0.0024/year ≃ 4% during the whole period of the simulation, which could be attributed to documented increasing trends of wind intensity and water volume transport in the region. The CUI exhibited the two most dominant peaks of variabilities on the range of annual and semi-annual timescales. The wind-stress southward component and the easting/westing veering of the northward EACC at 6°S revealed that these parameters were moderate and significantly correlated with the CUI (r = - 0.53 and 0.52, p<0.05) respectively, further suggesting its intensification during the Northeast Monsoon season.