A study of the variability of the amplitude of Sq at a fixed hour from one day to the next at nine stations from the dip equator to about 22° north of it has produced interesting results. The amplitude and sign of the variability change virtually randomly, making the mean practically zero. The variability occurs at all hours of the day. Its magnitudes in the components D, H and Z have the same diurnal variation, which peaks in the noon period like Sq(H) in low latitudes, and a weak seasonal variation that peaks at the June solstice (local summer). It is demonstrated that changes in the current intensities of the equatorial electrojet (EEJ) and the worldwide part of the Sq (W Sq) current layers have contrasting phases and can sometimes be in antiphase. Indeed, the changes are mostly independent. Inclusion of the magnetic element D revealed that the EEJ current system has not only an east–west but also a north–south component. The study shows that the meridional component of the EEJ current intensity evidenced at the Kodaikanal and Annamalainagar stations is an integral part of the zonal component at Trivandrum. This confirms the results of Rastogi (1996) and validates those of Onwumechili (1997). The results suggest that ionospheric conductivity mainly controls the magnitude, while the electric field and ultimately winds mainly control the phase and randomness of the day‐to‐day variability of the hourly amplitudes of Sq. The random component is attributed to local and/or regional atmospheric winds, probably of gravity wave origin.
Geophysical and physicochemical methods were carried out to examine the effect of leachate on groundwater in a dumpsite location in Akwa Ibom State, Nigeria. This was done to ascertain the level of organic contamination in the wells located in the study area. The analysis of water samples from boreholes close to the dumpsite was done to constrain the interpretation of electrical resistivity data on the reality of the effect imposed by dumpsite leachate on the hydrolithofacies. The resistivity values of the underlying layers were observed to be lower than the overlying layer, an effect which may be associated with the infiltration of leachate into the underlying layers. The geohydrolayer resistivities range from 78.4 to 1,669.8 Ωm. The contour maps generated display the variations of the parameters. The elevation contour map indicates the flow of groundwater in a southwest–northeast direction which also depicts the direction of leachate flow. The physicochemical water samples show differences in concentrations of the physicochemical parameters. The concentrations of the ions in the water samples measured are compared with the WHO standard for drinking water. The sodium absorption ratio and sodium percentage show that the groundwater within the dumpsite has no negative effect on the subsurface.
With the establishment of the new geomagnetic field observations in the Ocean Hemisphere Network Project (OHP) in Japan, minutes values of geomagnetic components, H D and Z have been recorded. The hourly mean values were used to study the variations in these three components at these new equatorial electrojet regions. The results of the analysis carried out revealed that the amplitude of d H has diurnal variation which peaks during the day at about local noon in all the three equatorial electrojet regions. This diurnal variation in H with Sq (H ) enhancement in all the three regions are attributed to the enhanced dynamo action at these regions. Diurnal variation as observed in D indicates that the equatorial electrojet current system has both east-west and north-south components. The pronounced magnitude of Z variation as observed in Kiritimati is attributed mainly to sea induction. Also some abnormal features were observed on 23rd of January at Huancayo, in the components. Seasonal variations with more pronounced equinoctial maximum were observed in H than in Z . D component showed no consistent seasonal variation in all the regions. The equinoctial maximum is due to enhanced equatorial electron density at equinox. More research work, if carried out in these new regions will be useful in making more new contributions to the field of the dynamics of the equatorial electrojet region.
Monthly precipitation data from meteorological stations in Nigeria are analysed from 1950 to 1992, in relation to sea surface temperatures (SSTs) in the tropical Pacific and Atlantic Oceans. The analyses have shed some light on understanding the variability of rainfall anomalies observed in Nigeria for this period. The correlation values between rainfall anomaly indices (RAI) and different meteorological indices are not all significant. Thus, the analyses show some indication that rainfall in Nigeria is associated with El Niñ o-related circulation and rainfall anomalies. The low correlations between RAI and SST in the Pacific confirm low correlations between rainfall and southern oscillation indices (SOI). SST correlations in the tropical Atlantic suggest that warm surface water in this part of the Atlantic moves the Inter Tropical Convergence Zone (ITCZ) southward and away from the SouthEast of Nigeria, indicating less rainfall, while, in SouthWest of Nigeria, the warm surface waters in this part of the Atlantic are likely to be responsible for a more northern position of the ITCZ, which produces more rainfall. The lower correlation in Northern Nigeria may be attributed to its continentality, away from the influence of the sea surface conditions in the Gulf of Guinea and the tropical Atlantic. The drought, or rainfall, cycles in Northern Nigeria are more closely connected to the land surface conditions in the nearby Sahel region.
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