Globally climate change has threatened agriculture and food security which is of great importance to the economy of a nation. In Nigeria it has become a great concern to the government and people because of the obviou...Globally climate change has threatened agriculture and food security which is of great importance to the economy of a nation. In Nigeria it has become a great concern to the government and people because of the obvious changes in the climate systems, therefore, assessing the impact of climate change on crop yield in an oil producing state is of great importance especially where rain fed agriculture is the main determinant for crop yield. Expost-facto research method in the context of quasi experimental research design was adopted for the study. Data for rainfall and temperature and that for crop yields were obtained from Nigerian Meteorological Agency (NIMET) and federal ministry of Agriculture;Agricultural Development Program (ADP) respectively. Analysis of data was achieved using descriptive statistics, trend graphs and multiple linear regressions. Results showed that there had been a steady but gradual increase in the annual minimum, maximum and mean temperatures over the study period of thirty years and a decrease in rainfall. Mean temperature is increasing annually at the rate of 0.0253 per annum and rainfall is decreasing at the rate of -0.5817 mm per annum. The multiple regression model showed r2 values of 0.28 for maize and 0.29 for cassava revealing that only 28% - 29% of maize and cassava yields could be explained by rainfall and temperature in the state and the result was significant at p < 0.05 revealing that cassava and maize yields significantly depended on rainfall and temperature. This study strongly advocates for a better and practicable environmental policies and improved agricultural techniques alternative source of water which will include irrigation farming, mulching since it is evident that there is a reduction in rainfall and increase in temperature in the state while creating sustainable food security.展开更多
Understanding the spatial distribution of temperature, especially the relationship between temperature and altitude, is essential for understanding both climatological and hydrological processes and their variabilitie...Understanding the spatial distribution of temperature, especially the relationship between temperature and altitude, is essential for understanding both climatological and hydrological processes and their variabilities. This is because those processes are sensitive to air temperature, especially in sub humid tropical regions, where air temperature influences the movements of pollutants and controls exchanges of energy and water fluxes between land and atmosphere particularly within the lower troposphere. This study examined the trend of lower tropospheric lapse rate in the coastal area of Port Harcourt, Nigeria. Six years’ data (2010-2015) for temperature between 1000 mbar and 850 mbar pressure levels was retrieved from era-interim re-analysis platform for the analysis. The data was acquired at 6-hourly synoptic hours: 0000H, 0600H, 1200H and 1800H at 0.125° grid resolution. Findings from the computed environmental lapse rate (ELR) show that conditional instability with an annual lapse rate of 5.5°C/km persists at the area from January to December. It was revealed that the months of December and January constituted the highest ELR trends of 6.5°C/km and 5.9°C/km respectively. This indicates that the month of December assumes a normal tropospheric lapse rate trend. The average range of lapse rate trend in the area which is close to the moist adiabatic lapse rate (MALR) of 5.0°C/km than the dry adiabatic lapse rate (DALR) shows that the study atmospheric environment is rich in water vapour. The 6-hourly synoptic analysis of the ELR pattern shows that lapse rate range between 1°C/km - 6.4°C/km and 6.5°C/km - 10°C/km dominates throughout the year at 0000 - 0600 Hrs and 1200 - 1800 Hrs respectively. This demonstrates a higher and lower lapse rate trend during the day and night periods respectively. Relating study findings to the potential of air to disperse emissions in the area suggests that air emissions will be conveyed through far and near distances across the boundary layers due to the moderate dispersive potential of air regarding the closeness of the average ELR to the MALR. Policies that will ensure that pollutants are dispersed aloft especially emission stacks above 50 m is advocated in the city of Port Harcourt.展开更多
Assessment of drought vulnerability and occurrence zones in North Central Nigeria was carried out in this study using standardized Precipitation Index (SPI). The Standardized Precipitation Index (SPI) 12 months’ time...Assessment of drought vulnerability and occurrence zones in North Central Nigeria was carried out in this study using standardized Precipitation Index (SPI). The Standardized Precipitation Index (SPI) 12 months’ time scale was computed from long-term rainfall data between 1960 and 2015 obtained from the Nigerian Meteorological Agency (NIMET) Abuja. The SPI results were further subjected to Mann-Kendal and Sen’s slope analysis for trend detection. To assess the vulnerability of drought and occurrence zones, the SPI and other geo-spatial techniques were employed to generate drought vulnerability maps for three epochs: 2000-2005, 2005-2010 and 2010-2015 respectively. The SPI values were interpolated using Inverse Weighted (IDW) techniques in ArcGIS10.5 to generate the vulnerability maps for the selected model years. The outcome of drought trend and vulnerability maps reveals increasing drought trend dominated by near normal and moderate conditions in Abuja, Ilorin and Lokoja while moderate and severe droughts were observed in Minna and Jos. The study therefore recommends holistic drought monitoring and management strategies in order to mitigate its adverse impact on water resources and rainfall-dependent agriculture.展开更多
This study examined the level of turbulence in the atmospheric boundary layer in Maiduguri, north-eastern Nigeria. Five years (2011-2015) temperature and wind speed data at 1000 mbar pressure level retrieved from Era-...This study examined the level of turbulence in the atmospheric boundary layer in Maiduguri, north-eastern Nigeria. Five years (2011-2015) temperature and wind speed data at 1000 mbar pressure level retrieved from Era-Interim Reanalysis Platform was used. These data were gotten at 6-hourly synoptic hours: 0000H, 0600H, 1200H and 1800H at 0.125° grid resolution. The gradient Richardson (Rig) number method was utilised in analysing turbulence across three layers: 10 - 50 m (surface layer);50 - 100 m (mid layer) and 100 - 1300 m (upper layer). Findings shows that the surface layer is always in a turbulent state as over 95% of Rig values were below Richardson Critical (Ric) value of 0.25 with range 0.02 - 0.94. However, all values across the hours were below the Richardson Termination (RT) value of 1. Laminar conditions exist at the mid layer across the hours as 99.9% of Rig values ranging 0.88 - 8.02 were greater than RT of 1. Rig values for the upper layer were largely negative and ranged between -78.71 to -724.14. This indicates robust turbulent conditions. Turbulence generated through forced and free ascents prevailed at the surface layer and upper layer respectively. This shows that wind shear is dominant at the surface while thermal buoyancy prevails at the upper level. The months of February and September at 1200 and 1800 hours respectively are the periods of maximum (about 134 m) and minimum (below 15 m) heights were free convection destabilises forced convection in the study area. Relating findings to emission dispersion suggests that air pollutants will be transported across far and near distances at the upper layer and surface layers respectively. This is due to the stable nature of the mid layer that will limits vertical emission dispersion. Policy makers should ensure that potential emission sources stacks are above 50 m to ensure pollutants are dispersed aloft in the area.展开更多
文摘Globally climate change has threatened agriculture and food security which is of great importance to the economy of a nation. In Nigeria it has become a great concern to the government and people because of the obvious changes in the climate systems, therefore, assessing the impact of climate change on crop yield in an oil producing state is of great importance especially where rain fed agriculture is the main determinant for crop yield. Expost-facto research method in the context of quasi experimental research design was adopted for the study. Data for rainfall and temperature and that for crop yields were obtained from Nigerian Meteorological Agency (NIMET) and federal ministry of Agriculture;Agricultural Development Program (ADP) respectively. Analysis of data was achieved using descriptive statistics, trend graphs and multiple linear regressions. Results showed that there had been a steady but gradual increase in the annual minimum, maximum and mean temperatures over the study period of thirty years and a decrease in rainfall. Mean temperature is increasing annually at the rate of 0.0253 per annum and rainfall is decreasing at the rate of -0.5817 mm per annum. The multiple regression model showed r2 values of 0.28 for maize and 0.29 for cassava revealing that only 28% - 29% of maize and cassava yields could be explained by rainfall and temperature in the state and the result was significant at p < 0.05 revealing that cassava and maize yields significantly depended on rainfall and temperature. This study strongly advocates for a better and practicable environmental policies and improved agricultural techniques alternative source of water which will include irrigation farming, mulching since it is evident that there is a reduction in rainfall and increase in temperature in the state while creating sustainable food security.
文摘Understanding the spatial distribution of temperature, especially the relationship between temperature and altitude, is essential for understanding both climatological and hydrological processes and their variabilities. This is because those processes are sensitive to air temperature, especially in sub humid tropical regions, where air temperature influences the movements of pollutants and controls exchanges of energy and water fluxes between land and atmosphere particularly within the lower troposphere. This study examined the trend of lower tropospheric lapse rate in the coastal area of Port Harcourt, Nigeria. Six years’ data (2010-2015) for temperature between 1000 mbar and 850 mbar pressure levels was retrieved from era-interim re-analysis platform for the analysis. The data was acquired at 6-hourly synoptic hours: 0000H, 0600H, 1200H and 1800H at 0.125° grid resolution. Findings from the computed environmental lapse rate (ELR) show that conditional instability with an annual lapse rate of 5.5°C/km persists at the area from January to December. It was revealed that the months of December and January constituted the highest ELR trends of 6.5°C/km and 5.9°C/km respectively. This indicates that the month of December assumes a normal tropospheric lapse rate trend. The average range of lapse rate trend in the area which is close to the moist adiabatic lapse rate (MALR) of 5.0°C/km than the dry adiabatic lapse rate (DALR) shows that the study atmospheric environment is rich in water vapour. The 6-hourly synoptic analysis of the ELR pattern shows that lapse rate range between 1°C/km - 6.4°C/km and 6.5°C/km - 10°C/km dominates throughout the year at 0000 - 0600 Hrs and 1200 - 1800 Hrs respectively. This demonstrates a higher and lower lapse rate trend during the day and night periods respectively. Relating study findings to the potential of air to disperse emissions in the area suggests that air emissions will be conveyed through far and near distances across the boundary layers due to the moderate dispersive potential of air regarding the closeness of the average ELR to the MALR. Policies that will ensure that pollutants are dispersed aloft especially emission stacks above 50 m is advocated in the city of Port Harcourt.
文摘Assessment of drought vulnerability and occurrence zones in North Central Nigeria was carried out in this study using standardized Precipitation Index (SPI). The Standardized Precipitation Index (SPI) 12 months’ time scale was computed from long-term rainfall data between 1960 and 2015 obtained from the Nigerian Meteorological Agency (NIMET) Abuja. The SPI results were further subjected to Mann-Kendal and Sen’s slope analysis for trend detection. To assess the vulnerability of drought and occurrence zones, the SPI and other geo-spatial techniques were employed to generate drought vulnerability maps for three epochs: 2000-2005, 2005-2010 and 2010-2015 respectively. The SPI values were interpolated using Inverse Weighted (IDW) techniques in ArcGIS10.5 to generate the vulnerability maps for the selected model years. The outcome of drought trend and vulnerability maps reveals increasing drought trend dominated by near normal and moderate conditions in Abuja, Ilorin and Lokoja while moderate and severe droughts were observed in Minna and Jos. The study therefore recommends holistic drought monitoring and management strategies in order to mitigate its adverse impact on water resources and rainfall-dependent agriculture.
文摘This study examined the level of turbulence in the atmospheric boundary layer in Maiduguri, north-eastern Nigeria. Five years (2011-2015) temperature and wind speed data at 1000 mbar pressure level retrieved from Era-Interim Reanalysis Platform was used. These data were gotten at 6-hourly synoptic hours: 0000H, 0600H, 1200H and 1800H at 0.125° grid resolution. The gradient Richardson (Rig) number method was utilised in analysing turbulence across three layers: 10 - 50 m (surface layer);50 - 100 m (mid layer) and 100 - 1300 m (upper layer). Findings shows that the surface layer is always in a turbulent state as over 95% of Rig values were below Richardson Critical (Ric) value of 0.25 with range 0.02 - 0.94. However, all values across the hours were below the Richardson Termination (RT) value of 1. Laminar conditions exist at the mid layer across the hours as 99.9% of Rig values ranging 0.88 - 8.02 were greater than RT of 1. Rig values for the upper layer were largely negative and ranged between -78.71 to -724.14. This indicates robust turbulent conditions. Turbulence generated through forced and free ascents prevailed at the surface layer and upper layer respectively. This shows that wind shear is dominant at the surface while thermal buoyancy prevails at the upper level. The months of February and September at 1200 and 1800 hours respectively are the periods of maximum (about 134 m) and minimum (below 15 m) heights were free convection destabilises forced convection in the study area. Relating findings to emission dispersion suggests that air pollutants will be transported across far and near distances at the upper layer and surface layers respectively. This is due to the stable nature of the mid layer that will limits vertical emission dispersion. Policy makers should ensure that potential emission sources stacks are above 50 m to ensure pollutants are dispersed aloft in the area.
