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This study examines long-term rainfall and temperature variations over a dry tropical environment in Nigeria. An assessment of the variations of these weather variables showcases the extent of climate change limits and corresponding effects on the biotic environment. Rainfall and temperature data were obtained from Nigerian Meteorological Agency for a period of 31 years (1991-2020) for Kano and Katsina States. Descriptive statistics were used to determine the degree of variability of the weather variables across spatial domains. Results showed that there is a sharp contrast in mean annual rainfall amounts of 1154.1 mm and 569.6 mm for Kano and Katsina located in the dry continental and semi-arid climate zones of Nigeria respectively. It is revealed that the month of August had the highest mean monthly rainfall for both areas i.e. 359 mm and 194 mm with little or no trace during the dry season. The sharp difference in rainfall amount across spatial domains of the near similar climate zones shows that the Inter-tropical Discontinuity (ITD) does not completely overwhelm the northern band of Nigeria in August. The least variable monthly rainfall was in August and July with coefficient variations (CV) of 40% and 47% for Kano and Katsina. The months of February and March had the highest CV of 557% and 273% for the respective areas. In the examined areas the wet and dry seasons are from June-September and October-May respectively. The index of rainfall variability and drought intensity for the areas ranged from 0.85-0.95 and 45% indicating moderate variability and drought respectively. Mean annual temperature values are 33.4 °C and 33.8 °C for Kano and Katsina. The study recommends a proper climate observing scheme, most especially for agrarian practices so as to ensure profitable outputs for human sustainability.

The air quality index (AQI) of a location informs how clean or unhealthy the ambient air is. While COVID-19 pandemic on one hand threatened the health of mankind globally, on the other hand was a respite to poor air quality of most cities. This study evaluated the positive effects of the brief COVID-19 lockdown on the air quality of Port Harcourt city, Nigeria. Air quality parameters aimed at assessing air quality index of Port Harcourt Metropolis before, during and after COVID-19 pandemic lockdown were monitored and compared. Data were analysed and AQI of sampled locations computed using the US EPA recommended standard procedure. Results from the study showed that, the ambient air quality of Port Harcourt was hazardous for breathing before lockdown. During shutdown of activities, the air quality improved to unhealthy status, with an average reduction AQI of 261.7 points. However, an average increase of 100.7 points, resulting to very unhealthy air status for residents after lockdown was observed. The unhealthy status during lockdown shows that anthropogenic activities were still on despite the Pandemic shutdown of economic activities. Also, decrease in levels of the criteria air pollutants was observed. Before lock down, the range levels of SO3, NO2, CO, O3, PM2.5 and PM10 were 3, 15 - 135 μg/m3, respectively. In the period of lockdown, the levels reduced considerably, especially CO and PM2.5 and PM10 (1 - 12 ppm, 5 - 60 μg/m3, and 10 - 50 μg/ m3). Conversely, after lockdown, there was upsurge in levels of the pollutants, especially CO and PM2.5 and PM10 (4 - 16 ppm, 10 - 110 μg/m3, 10 - 90 μg/m3). Authorities are expected to establish routine air quality measurements stations and communicate daily air quality to residents, for public health precaution purposes. Shutdown of industrial activities instituted by Government in curtailing the surge of COVID-19 pandemic could likely be a novel environmental model for mitigating air pollution in highly hazardous air pollution emergency domains.

This study surveyed the levels of boundary layer surface turbulence across a West African climate region. Five years (2011-2015) temperature and wind speed data at synoptic hours 0000 Hr, 0600 Hr, 1200 Hr and 1800 Hr within 0.125° grid resolution was sourced from Era-Interim Reanalysis platform at 1000 mbar pressure level. Using the Richardson (Ri) number technique, results showed that mechanical turbulence of Ri range 0.04 - 0.57 dominates across the surface layer for study locations of Port Harcourt, Enugu, Jos, Kano and Maiduguri than thermal turbulence. However, the least turbulent area was the coastal zone of surveyed region. Results also indicated that the vertical height (L) at which thermal turbulence replaces mechanical turbulence across study locations ranged from 20 - 250 m with lowest replacement levels (20 - 50 m) occurring mainly in the coastal area of Port Harcourt during periods of dawn. The most turbulent periods in the southern coastal location of study region were during key rainy periods from June-August while that for the rest far northern inland areas occur during the dry season/early rainy periods i.e. November-May. The implication of the lower surface turbulence/replacement level within coastal domains most especially during periods of dawn is that emission releases near surface layer will be dispersed after initial rise due to buoyancy at horizontal levels thereby increasing ground level pollutants concentration across sensitive receptors that are close to emission source. At heights of thermal turbulence replacement, emission releases will be transported vertically and then dispersed further away from emission sources, thus impacting sensitive receptors at farther distances. This is the atmospheric boundary layer dynamics that makes ground level pollution worse in the coastal city of Port Harcourt in recent times during periods of dawn. Efforts must be made by concerned Stakeholders towards ensuring that emissions are reduced during the periods of dawn within and around coastal environments.

In recent years, urban air quality in developing countries such as Nigeria has continued to degenerate and this has constituted a major environmental risk to human health. It has been shown that an increase in ambient particulate matter (PM10) load of 10 μg/m3 reduces life expectancy by 0.64 years. Air Quality Index (AQI) as demonstrated in this study shows how relatively clean or polluted the boundary layer environment of any location can be. The study was designed to measure the level of suspended particulate matter (PM2.5 and PM10) for dry and wet seasons, compute the prevalent air quality index of selected locations in Abuja with possible health implications. Suspended particulate matter (PM2.5 and PM10) was assessed using handheld aerosol particulate sampler. The US Oak Ridge National AQI was adopted for the eleven (11) locations sampled and monitored. The study results showed that the air quality of the selected areas in Abuja were generally good and healthy. Dry season, assessments, showed 15 - 95 μg/m3 and 12 - 80 μg/m3 for PM2.5 and PM10, respectively. While in wet season, 09 - 75 μg/m3 and 07 - 65 μg/m3 were recorded for PM2.5 and PM10. However at Jebi Central Motor Park, there was light air contamination with AQI of 42 for dry season and 31 for wet season. Other locations had clean air with AQI ≤ 11. It is revealed that clean air exists generally during the wet season. Comparing study outcome to other cities in Nigeria, residents of Abuja are likely not to be affected with health hazards of particulate matter pollution. Nonetheless, the high range of PM2.5 and PM10 (fine and coarse particles) ratio evaluated i.e., 1.06 - 1.79 was higher than the WHO recommended standard of 0.5 - 0.8. This ratio remains a health concerns for sensitive inhabitants like pregnant women and their foetus as well as infants below age five whose respiratory airways are noted to have high surface areas and absorption capacity for fine particulate matter. Vegetation known to absorb suspended particulate matter should be planted across Abuja metropolitan areas and air quality monitoring stations installed at strategic locations for continuous monitoring and evaluations.

This study assessed the pattern of planetary layer lapse rate across the major climate belts of Nigeria. Six years’ data (2010-2015) for air temperature values between 1000 mbar and 850 mbar atmospheric pressure levels were acquired from Era-Interim Re-analysis data centre. The data was retrieved at 6-hourly synoptic hours: 0000H, 0600H, 1200H and 1800H at 0.125o grid resolution. Results showed that the lower tropospheric layers throughout the various climate belts has a positive lapse rate. Findings also revealed that the average annual lapse rate condition were: Tropical wet zone (Port Harcourt) -5.6 oC/km; Bi-modal Tropical continental zone (Enugu) 5.8 oC/km; Montane zone (Jos) -6.5 oC/km; Mono-modal Tropical continental zone (Kano) -6.6 oC/km; and Hot semi-arid zone (Maiduguri) -6.6 oC/km. This average values presents the lapse rates to be close to the Saturated Adiabatic Lapse Rate (SALR). Average diurnal results for the climate belts showed that lapse rate is higher during the afternoon and transition periods than the rest periods and increases from the coastal areas northward. The seasonal periods of highest lapse rates during the day time are from December – May (i.e. 5.8-9.5 oC/km) with slight decrease from June – November. The positive lapse rate of range -1.8 – -5.9 oC/km observed during the period of dawn across the entire region showed that infrared radiation was still being released and modified by less energetic mechanical turbulence that characterizes the surface layer across Nigeria. This also indicates that global warming is real and in substantial effect. The study findings imply that conditional instability prevailed over the entire region, therefore, the planetary layer environment will be of slow to moderate dispersive potential and will require forceful mechanism to lift emissions are introduced into it. It is recommended that industrial stacks are above 50 m to enhance the dispersion of emissions aloft.

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.

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.

While millions of deaths are recorded from COVID-19 pandemic infection, the environment continues to benefits from the lockdown of cities. A descriptive cross-sectional survey aimed at assessing residents’ knowledge and perception concerning air pollution and breathing experience in Port Harcourt was carried out within 20th-28th of May, 2020. Convenience and purposive non-randomized sampling methods were used to recruit 358 participants. Using descriptive and chi square test analysis, majority (74% and 24%) of the respondents were very aware or aware of air pollution and its health consequences. This varied significantly with sex, age, marital status, occupation and location (p < 0.05). Before the city’s lockdown, 90.1% of respondents experienced particulate matter deposits on surfaces and during the lockdown; it reduces to 54.1% with significant difference (p < 0.05) across residential areas. Hence, age, sex, marital status, occupation and residential area likely to influence higher awareness of air pollution and not duration of stay. Also, significant difference in breathing experiences (p < 0.05) was noted, with majority reporting poor breathing experience before lockdown and good during the lockdown. Joint action of governments’ policies on air pollution and high awareness among residents could be explored effectively to mitigate air pollution hazards.

There is no systematic attempt to evaluate the air quality of any settlement in the Niger Delta region over a long period. Records of air quality data for this study were generated through secondary sources from impact assessment of facilities aimed at implementing air quality regulations on the environment. Suspended particulate matter in the region’s atmosphere ranged from 40 mg/m3 in Brass to 98 mg/m3 in Port Harcourt. Carbon monoxide concentrations were highest in Mbiama (191 mg/m3). Nitrogen dioxide concentration was highest in Bonny (187 mg/m3), and sulphur dioxide concentrations ranged from 19 mg/m3 in Ukwugba to 90 mg/m3 in Port Harcourt. Total hydrocarbon ranged from 78 mg/m3 in Odukpani to 192 mg/m3 in Nchia. Carbon dioxide ranged from 400 ppm in Buguma to 450 ppm in Port Harcourt. The most abundant of the VOCs is benzene and toluene. Ethylene was detected only in one station at concentration of 0.1 mg/m3 which was negligible. The most abundant of the metals was zinc, which was present at above 2 mg/m3 in most of the study settlements. In remote settlements like Buguma and Emuoha, some of the metals were not detected at all. In some instances, short-term limits for the pollutants exceeded WHO standards. The need for stakeholders in the region to articulate initiatives that support quality environmental practices was emphasized as laws pertaining to air quality regulations which are weak and less enforceable.

The Bonny Island axis of the Niger Delta, Nigeria, is one of the most industrialized belts of Nigeria. Among the significant industries in the locality is the Nigerian natural gas liquefying plants. The plant complex generates emissions which are propagated by meteorological agents. An atmospheric dispersion model was used to model the emissions using a computer programme. A statistical analysis of meteorological parameters was also carried out to determine the pollutants dispersion in the atmosphere. The analysis shows that wind speed is moderate and the predominance of southerly winds will move plumes toward human settlements in the north and north-eastern directions from the plant. From the diffusion model, the compounds likely to be emitted in the largest quantity from the plant in the order of magnitude were CO2, NOx, CO, PM10 and SOx. There is evidence that pollutants concentration would be highest for receptors at about 10 km from the emission sources even under unstable atmospheric conditions. The concentration of all the pollutants were well within the set ambient limits for the averaging period considered (i.e., 1 hour). It is recommended that the LNG plants continue to use natural gas as their major fuel as it will help in reducing pollutants like CO, PM10 and SOx. Also, due to the large CO2 gas emitted, afforestation and conservation projects should be initiated in Bonny Island so as to earn carbon credit.