by Mlawa, A., Saria and E. E
Original Research
Atmospheric water vapour (AWV) is one of the parameters that affect GNSS signals in the troposphere, however this parameter is very important conservatory gas which helps to maintaining Earth’s energy balance and the hydrological cycle. The AWV is one of the fundamental meteorological parameter in numeric weather prediction. In many years this parameter has been computed using conventional methods including radiosondes, microwave radiometer, and hygrometers. However, these methods are facing numerous challenges including inadequacy, low spatial and temporal resolution and high maintenance cost. Given the high investment required and maintenance cost, the Tanzania Meteorological Agency (TMA) had only four radiosondes across the country. With advances in technology Global Navigation Satellite system (GNSS) are replacing the conventional methods due to its capability to determine Precipitable Water (PW) or Integrated Water Vapour (IWV) at low cost. The aim of this study is to use a yearlong GNSS data from Dodoma CORS station in Tanzania to compute PW or IWV and compare with global weather models. The results from this comparison will help TMA to decide on better methods for weather prediction. In this study, the datasets were processed using gLAB and GAMIT/GLOBK software based on two processing strategies weather free and weather dependent approaches. The results from this processing were analyzed against Global weather model particularly the products from ECMWF Reanalysis - Interim (ERA-Interim). The result shows that GNSS results from gLAB and GAMIT/GLOBK have good agreement with a correlation <0.98 while between GNSS and the ERA-Interim model values shows a correlation <0.96. Given these correlations, this study provides great indication of how GNSS data can be used to retrieve the key meteorological values for weather prediction in Tanzania and provide great assistance to the Tanzania Meteorological Agency (TMA).
Journal of Geosciences and Geomatics. 2023, 11(3), 88-96. DOI: 10.12691/jgg-11-3-3
Pub. Date: November 06, 2023
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by Sanmi O. Odeyemi, Dominic Fontana, Eberechi Ichi, Ene S. Ajonye and Ossai Alu
Original Research
The vulnerability of coaster regions to flooding due to extreme sea level rise and storm surge has become notable since the late 20th century to date this 21st century. This vulnerability can be attributed among other things to the global rising sea level due to anthropogenic climate change. A platform is needed to integrate the necessary data to mitigate the impact of flooding and aid plans intended to safeguard these vulnerable regions. Geographic Information Systems (GIS) technique has given that stage by which different bits of past, present, and future information can be incorporated to get spatial-based data, from which areas in danger of unavoidable flood peril can be recognised. This study utilised GIS techniques to develop a spatial flood model of rising sea level scenarios. The expected rising sea level data (RCP 4.5 scenario), LiDAR Digital Elevation Model (DEM), estimated 2011 UK census, and the building & height alpha data were used to estimate the approximate number of buildings that might be exposed to inundation. Also, an estimated number of people that could be affected and land area were obtained. The outcome shows that for 3.11mOD extreme rising sea level value, 1074-unit houses, 2.79km2 (6.91%) of the land area were inundated with an estimated population of about 2,000 people. Whereas for the 3.59mOD rising sea level value, 14,500-unit houses, covering 4.63km2 (11.5%) of land were immersed, with an estimated population of about 71,500 people. The result also shows, among other places in the city, that an estimated 5,900-unit building and 33,931 people will be impacted in the south, Southsea, and Portsea areas. In comparison, about 5,000 structures and 17,500 people will be affected on the eastern side of Portsea Island. These areas were distinguished as regions possibly in danger of coaster flooding because of storm surges and extremely rising sea levels.
Journal of Geosciences and Geomatics. 2023, 11(3), 79-87. DOI: 10.12691/jgg-11-3-2
Pub. Date: July 25, 2023
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by Ukpebor Osahon and Maju-Oyovwikowhe Gladys Efetobore
Original Research
This study focuses on the identification and delineation of hydrocarbon-charged reservoirs in the SJ field of the Niger Delta Basin using an integrated rock physics modeling approach. The study design encompasses the integration of rock physics modeling, shear wave logs, and fluid substitution techniques. The research was conducted in the SJ field of the Niger Delta Basin, spanning from January 2022 to January 2023. Shear wave logs were empirically generated using the Castagna mud rock line relationship, and fluid substitution techniques were applied to obtain accurate log values for hydrocarbon-bearing intervals. P Impedance (Zp) and S Impedance (Zs) were inverted from P wave reflectivity (Rp) and S wave reflectivity (Rs) using a model-based inversion method. Several attributes, including μρ (mu-rho) and λρ (lambda-rho), were generated to discriminate between rock lithologies and differentiate gas-sand from wet-sand reservoirs, based on equations proposed by Castagna. Crossplot analysis of well log data was conducted to validate the presence of gas in the target zone. The results of the crossplot analysis confirmed the presence of gas in the target zone, providing support for the identification of hydrocarbon-charged reservoirs. Additionally, the generated attributes, such as μρ, λρ, and λ/μ, offered valuable insights into the distribution and extent of the gas reservoir. In conclusion, the integrated approach of rock physics modeling, shear wave logs, and fluid substitution techniques proved effective in identifying and delineating hydrocarbon-charged reservoirs in the SJ field of the Niger Delta Basin. The analysis of various attributes derived from inversion and crossplotting techniques facilitated the prediction of the spreading of the gas reservoir, highlighting the significant potential of this approach for reservoir characterization and development.
Journal of Geosciences and Geomatics. 2023, 11(3), 67-78. DOI: 10.12691/jgg-11-3-1
Pub. Date: June 22, 2023
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