Nature of the rain spectrum at a low latitude coastal station

The internal structure of rain falls in terms of rain rate during various instances of time can be determined by measuring rain amounts received during very short intervals of time. A system that can record the intensity of rain fall at every minute has been used for this study.

Station hydrologique cotière d'Abidjan de 1966 à 1980

In this document the monthly T-S diagrams and the regression lines of the temperature and salinity two weeks mean values have been drawn for 0, 5, 10, 15, 20 and 25 meters of depth. The annual variations of the dynamic height anomaly are represented for every coastal station from 1966 to 1980.

Stations cotieres et station hydrologique cotiere d'Abidjan: annees 1980-1981

Beach surface temperature is recorded every morning between 7h30 and 8h00 at each coastal station. On figure 2, 3, 4 and 5 it has been plotted daily variation and mean variation computed on 7, 15 and 30 days basis of sea surface temperature. However it seems that variations of dynamic height anomaly are reflecting more accurately the stages of the coastal upwelling than the sea surface temperature.

Les saisons marines devant Abidjan

From March 1966 to March 1970 some hydrographic observations were collected twice a week at a coastal station, off Abidjan. These data show the alternation of well defined water masses over the Ivorian Continental shelf. Grouping all observations on a T-S diagram, it is possible to differentiate four marine seasons, which are typical of an austral type of climate such as is observed off Pointe Noire.

Variation des bio-volumes des zooplancton du plateau continental entre le Cap des Palmes et le Cap des Trois Pointes

Three years of weekly sampling from a coastal station and 29 monthly cruises over the whole continental shelf were studied for zooplankton quantitative variation. Settled volumes were preferred to displacement volumes. At the coastal station, near Abidjan, a negative correlation was found between the log2 of zooplankton volume and the preceding fortnight temperature. On the whole shelf, the differences between the 6 considered areas were tested by the variance analysis. There were significative differences in shallow waters only (20 m). During the main cold season, the upwelling of Tabou causes a very important enrichment 30 to 60 nautical miles to the east. Eastwards the plankton drifts and decreases in abundance. The zooplankton maximum is not always inshore, but often in the middle of the shelf and sometimes over the slope. During the little cold season the enrichments caused by coastal upwelling are less abundant and restricted to smaller areas. During the warm season, the waters are uniformly poor. During the cold season, over the 60m depths, the zooplankton maximum lies between 10 and 20 m and seems to sink in deeper waters. In warm season the vertical repartition is rather homogeneous in the first 40 meters. The diel vertical migrations show a very consistent rhythm, varying with the season.

Estimation de la production zooplanctonique sur le plateau continental ivoirien

An attempt was made to calculate zooplankton production from weights and settled volumes and from the life cycle of some copepods. Biomass data were recorded during several years from 24 monthly cruises and from a coastal station sampled biweekly. Dry weight data were directly measured or were calculated from the settled volumes using a linear regression. They range, on an average, from 0.965 to 5.56 g m-2 day-1 from the shore line to the edge of the continental shelf. The mean life-span of the cohorts of 12 species of copepods is about 20 days. It is assumed that only 1 spawn occurs per generation-time and that the standing stock is turned-over during the life span of a cohort. The production ranges from 48.2 to 278 mg dry weight m-2 day-1 or 17.9 to 103 mg C m-2 day-1, according to the depth of the studied areas. One third of carnivorous production occurs among the copepods. So, it is assumed that the herbivorous and omnivorous production is about 2/3 of the total zooplanktonic production. This would be a more accurate estimate of secondary production. The standing stock of zooplankton and fishes are in the same order of magnitude; the ratio zooplanktonic production/total fishery is 0.8%.

Tidal and sea level changes at Jeddah, Red Sea

Tidal and sea level changes during 1991 at a coastal station (Jeddah) in the central part of the Red Sea are investigated. Analysis shows higher sea levels in winter and lower in summer. The amplitude of change at Jeddah is above 50cm. Analysis of wind stress at Jeddah indicates an insignificant contribution of the cross-shore component, while a major part of the changes in the sea level can be accounted for by the long-shore component.