MODELLING GEOIDAL HEIGHTS IN THE GULF OF GUINEA USING JASON-2 SATELLITE ALTIMETRY DATA
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Date
2019-10-03
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Ahmadu Bello University Zaria
Abstract
Satellite Altimetry is an aspect of the microwave remote sensing and
space geodesy, used for the study of global mean sea level, sea surface
topography,which can be related to the ellipsoid, geoid, wetland water- level
monitoring, geophysical exploration and so on. The over flow of water to the
Rivers resulted from the rise in Global Mean Sea Level and the changes in the
Global Mean Sea Level is better evaluated and understood from a good
estimation of reference surface such as ellipsoid and geoid. This study aims at
modelling the Geoid heightover the Nigerian Gulf of Guinea Waters fromsatellite
altimetry data for a proper understanding of thesurface heights of the Gulf of
Guinea relative to the mean sea level using JASON-2 satellite altimetry data.
The data used for the study isJASON-2_GDR
(gridded_3×1deg_cycle_mean.nc)products of combined altimetry datasets for a
period of seven (7) yearsfrom July 2008 to 2015. The Mea Sea Surface (MSS), the Mean Dynamic Topography (MDT) and the Geoid height were estimated on latitude -2 to 6 (degree) and longitude 2 to 10 (degree) of the Gulf of Guinea.The sampling was done using Panoply 4.8.3/Java 8 Runtime Environment
Software.ArcGIS 10.2.2 software was employed to perform the geo-statistics Inverse Distance Weight (IDW) interpolation for estimating the missing points and the Geoid height surface modelling/interpolation.
Linear trend analysis was carried out to estimate the accuracy of measures using Mini tab 18 software where Mean Absolute Percentage Error (MAPE) and the results reveal that, the MSSH, MDT and the Geoid heightwere 2.59269,1.13365 and 2.66622 respectively.The Mean Absolute Deviation (MAD) for MSSH, MDT and Geoid height were 0.46276, 0.00442 and 0.46532, while the Mean Square Deviation (MSD) wereestimated as 0.34472, 0.00003 and 0.348860 for the MSSH, MDT and Geoid height respectively. The Geoid heightmodels had poor accuracy value with estimate of about 2.7% Mean Absolute Error over the sampled years compared with the MSSH and MDT models of about 2.6% and 1.1% respectively. Theautocorrelation between MSSH, MDT and Geoid
heightwere found to be strong with Durbin-Watson value of d = 0.006, which is below the two critical values 0f 1.5 < d< 2.5. In addition, the trend for the models were projected from 2016 up to 2022.
The MSSH projected an estimate of the range between 17.90m to 19.10m, the MDT projected a range between 0.394m to 0.417m and the Geoid projected an estimate of 16.52m to 18.25m on a sampled data of every July month of the year only. Knowing the trend of the sea surface heights of Nigeria Gulf of Guinea, further research can be carried out to determine how the Nigeria coastal States and climate change can be affected with this trend.