Harmattan Research Articles

Aerosol loading in the guinea coast climate region of Nigeria: comparison of MODIS and AERONET data sources

This study compares aerosol optical depth (AOD) measurements from satellite data with that from a ground-based station. It aims at validating monthly AOD data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue (DB) collection 6.1 (Aqua and Terra) at 550 nm against AOD data from the Aerosol Robotic Network (AERONET) station at 500 nm in Ilorin over the period 2003–2022. The analysis focuses on eight selected cities/locations within the Guinea Coast region of Nigeria. Descriptive and inferential statistical methods, including correlation, regression, standard deviation, coefficient of variation, the Mann–Kendall trend test, root mean square error (RMSE), mean absolute error (MAE), and relative mean bias (RMB), were employed. The results indicate a positive correlation in most locations, with correlation values ranging from 0.3 to 0.7. The correlation between the datasets in Ilorin showed a positive and significant relationship while the other seven locations presented a weak and insignificant relationship. Additionally, the period from 2013–2022 showed better correlation compared to 2003–2012. AOD levels were highest during the harmattan season (DJF), exceeding 0.8, and lowest during the monsoon (JJA) and post-monsoon (SON) seasons, with values below 0.5, reflecting the effects of wet scavenging. The highest agreement between MODIS Aqua and AERONET data was observed during the harmattan season. The study also found that MODIS tends to overestimate AOD compared to AERONET and that MODIS-AOD exhibits greater spread and variability than AERONET-AOD.

Influence of changes in solar activity on Nigerian Rainfall

This paper focuses on the impact of solar activity changes on rainfall in Nigeria. Rainfall data were got from Gridded Time Series (CRU TS v4) of the University of East Anglia, United Kingdom. Various statistical tools like Pearson rank correlation coefficient, regression analysis, covariance, skewness, and kurtosis are employed in the study. The results show that there are generally weak correlations between rainfall and solar activity in most seasons. However, low correlation coefficients (0.0424 and 0.1040, respectively for sunspot numbers and F10.7 mean a very weak positive relationship between early rainfall, main rainfall and annual rainfall and negative for dry season rainfall and Harmattan rainfall. Also, there is a negative time-series relationship between the rainfall amount in dry and Harmattan seasons, with the highest rainfall amount during low solar activity and vice versa. Therefore, it can be concluded that solar activity has little effect on Nigeria's annual and main season rainfall. However, during the dry season and Harmattan, heavy rainfall appears to be associated with low solar activity, while high solar activity appears to be associated with low rainfall. This study will be beneficial to farmers in Nigeria, majority of whom are peasant farmers that practice rain-fed farming.

Potential of low-cost PM monitoring sensors to fill monitoring gaps in areas of Sub-Saharan Africa

Recent advances in low-cost (LC) sensor technology fostered their deployment in low-income and undersampled countries such as Sub-Saharan Africa (SSA) regions, affected by the highest particulate matter (PM) concentrations and population exposure. The present study is the first addressed in Niamey, Niger, and focuses on assessing LC sensor data and global reanalysis products. Three LC PM2.5 and PM10 monitoring stations were deployed and successfully operated across ∼8 months at different (urban, suburban and rural) locations.Observed PM2.5 and PM10 concentrations revealed consistent patterns, higher during the dry Harmattan season, while appreciably lower during the humid monsoon season. In Niamey, PM2.5 mean concentrations (6.1–20.1 μg/m3) were similar to those observed over higher-income countries, confirming the hypothesis of strictly depending on urbanisation, and thus on anthropogenic activities. Conversely, PM10 concentrations (55.3–142.8 μg/m3) were remarkably higher than most of those measured elsewhere worldwide, and predominantly constituted (81–89%) by coarse fraction. PM10 origin, inferred by backtrajectory analysis, was mainly natural (Saharan dust) during the Harmattan season, and both natural and anthropogenic during the monsoon season.Low-resolution gridded estimations by the Copernicus Atmosphere Monitoring Service (CAMS) were not capable of adequately resolving the spatial variability of PM2.5 and PM10 observations in Niamey, further highlighting the importance of sensor network data to improve air quality knowledge. To tackle the harmful effects of Saharan dust on population, and create robust datasets integrated with gridded products in this challenging region, effort should be put toward creation of trans-national integrated monitoring networks based on LC sensors across SSA.

Severe Cold Harmattan Events in the Northwestern Region of Nigeria from 1961 to 2020

This study examined the occurrences of severe cold harmattan events in Northwestern Nigeria from 1961 to 2020. Monthly minimum temperatures of the harmattan seasons (November to February) for five (5) selected stations: Kaduna, Kano, Gusau, Katsina, and Sokoto, were collected and analyzed over 60 years. A modified Standard Anomaly Index (SAI) was applied to determine the severe cold harmattan (SCH) events for the harmattan seasons. Findings revealed that SCH events occurred 55 times in the study area throughout the study period. In terms of geographical distribution, Sokoto experienced the most frequent SCH events (16 times in 60 years), followed by Kano and Katsina (15 times each). Kaduna had the lowest frequency (3 times), next to Gusau (6 times). Among decades, the second decade (1971-1980) had the highest occurrences of SCH in the study area (15 times in 10 years or 27.27%). Sokoto experienced the highest occurrence in this decade, while both Kaduna and Gusau witnessed the lowest. In regards to total decadal frequency, the most recent decade (2011-2020) and the first decade (1961-1970) tied for second. In general, all stations experienced SCH in the most recent decade (2011-2020). The study suggests that measures should be put in place to mitigate against SCH events that focus on climate change abatement strategies such as conventional mitigation, reduction of negative emissions, and unpleasant land use practices because climate change can increase the frequency of SCH and may put human health at risk of cold-related illnesses.

Application of Multivariate Logistic Regression and Decision Trees to Assess Factors Influencing Prevalence of Abortion and Stillbirth in Yankasa sheep

AbstractThis study was carried out to assess factors influencing prevalence of abortion and stillbirth in Yankasa sheep using multivariate logistic regression and decision trees. 191 kidding records of Ewes from a total of 50 traditional Yankasa sheep herders within Nasarawa South agro-ecological zone from the year 2020-2021 were utilized in the study. Sampling was restricted to only farmers that were able to give information on Lamb, Ram and Ewe identification as well as occurrence of abortion, stillbirth (defined as a kid born dead or dying within 24 hours after birth), kidding date or period, parity and number of foetuses. Three seasons of abortion or stillbirth were generated according to the month of the year: rainy season (from May to October), dry season (from February to April) and harmattan season (from November to January). The logit of the probability of an abortion or stillbirth was modelled using logistic regression assuming an asymptotic binomial distribution. The Chi-square goodness of fit test was performed to check if the multivariate logistic model fitted the data well (P>0.05). Chi-square automatic interaction detection (CHAID) algorithm was also employed to model incidence of abortion or stillbirth. The chi-square analysis revealed that parity did not significantly (P>0.05) affect the incidence of abortion. However, season of the year significantly (P<0.05) affected prevalence of abortion, which was higher in the harmattan (38.5%) compared to the rainy (11.5%) and dry season (16.5%), respectively. Parity and season of the year did not affect significantly (P>0.05) the prevalence of stillbirth. The binary logistic regression analysis showed that season affected significantly (P<0.05) the prevalence of abortion, especially in the harmattan period with a high odds ratio (4.539). This was also confirmed by the result of the CHAID analysis. The present information could be exploited in management practices to reduce to the incidence of abortion in order to improve the production level of the sheep farmers.

Survey of Hausa Traditional Fish Fence Usage in Zamfara, North-West Nigeria

Artisanal fishing is a traditional occupation that exists among the Hausa people of Zamfara state, North-West Nigeria. This is made possible due to the presence of water resources which vary both in form and size. The region is blessed with six (6) rivers that traverse through it. These rivers are tributaries that emptied their volume of water into river Niger. These rivers become filled up with water during the rainy season and sometimes overflow their banks so much so that the floodplain areas of the state become over flooded, including the lakes that are found around Shikafi, Bakura and Gummi areas. The notable lakes in Zamfara include the Tafkin Jenna in Zurmi, the Nato in Bakura, the Saru Lake in Gummi and the Kalale Lake in Ɗangulbi of Maru Local Government. These lakes aside, the state is blessed with other smaller lakes and manmade water reservoirs, notable of which is the Bakalori dam of Maradun. The availability of these fishing grounds made it possible for a section of the population to engage in artisanal fishing as a means of sustenance for their livelihoods. The Zamfara fishermen make use of numerous techniques to enhance their catch. This paper is an attempt to explore the techniques of fishing fences, especially their type, construction and efficacy in enhancing catch. Through surveys and trips to selected fishing grounds, the paper concludes that traditional fishing fences form part of greater ways by which the fishermen enhance catch, especially during the dry season when the lakes’ water level has drastically reduced in volume due to the elapse of rain coupled with the effects of dry winds of the Winter (Harmattan) season which sets in around November through to February of each year.

Dust soiling effects on decentralized solar in West Africa

West Africa’s proximity to the Sahara Desert can cause photovoltaic (PV) systems to experience significant power generation reductions when particulates settle onto solar panel surfaces in a phenomenon known as soiling. Previous studies have created models to estimate PV soiling globally, but these models have several limitations in the region due to the accuracy of the input particular matter (PM) concentration values, the accuracy of methods for computing power loss, and the regional use of decentralized solar systems. Here we develop and apply a methodology for the development of a soiling estimation model based on the Coello framework, and evaluate it when using input PM concentration values from both a reanalysis dataset (MERRA-2) and a dataset derived from satellite-observations (WUSTL). This model reduces error in soiling-related power loss estimates by approximately 50% when compared to the unadjusted Coello approach. Using this model, we find soiling losses can exceed 50% in the most greatly affected locations during the Harmattan season and these power losses can vary considerably each year (between 26 and 53% in Niamey, Niger). To support PV system design, we develop a function that relates maximum soiling losses to annual cleaning frequencies in major cities. Finally, we find if decentralized solar is used to meet electricity access goals as projected, PV cleaning costs could sum up to $1Bn (USD) annually in sub-Saharan Africa by 2030.

Evaluation of real-time monitored ozone concentration from Abuja, Nigeria

Real-time ozone (O3) concentration is vital for accurate analysis of O3 to inform the public about O3 concentrations that may have an adverse effect on health. Few studies have analysed air pollution in Abuja, Nigeria and non on real-time ozone concentrations. As a result, there is a scarcity of data and information on real-time ozone pollution, pointing to a gap that needs to be urgently closed to enable a better understanding of ozone pollution and the causes and consequences in terms of the associated health risks.In this study, -time concentrations of ground-level ozone were measured in a busy urban pollution monitoring station. Using a real-time ozone monitor to enable real-time monitoring of O3 concentration of ozone for the first time in Abuja. The ozone concentrations followed a clear pattern with high concentrations being recorded during the dry (harmattan) season. Concentrations higher than the WHO standard of (eight-hour averaged) 100 µg/m3, occurred on 53 days over the 5-month dry season. Of those 53 days, 18 had ozone concentrations greater than 200 µg/m3. Daily patterns showed a rise throughout the day, reaching a peak in the evening. Weekday/weekend differences were less pronounced than those found in other studies. High temperatures and local climatic conditions in Abuja encourage the formation of ozone. In this study, we confirm the concentration of ozone, and the pattern can be episodic and potentially damaging to health. There is a need for better regulation and measures to reduce ozone, particularly when local climatic conditions, such as harmattan, favour the development of photochemical smog in such settings.

High-resolution patterns and inequalities in ambient fine particle mass (PM2.5) and black carbon (BC) in the Greater Accra Metropolis, Ghana

Growing cities in sub-Saharan Africa (SSA) experience high levels of ambient air pollution. However, sparse long-term city-wide air pollution exposure data limits policy mitigation efforts and assessment of the health and climate effects. In the first study of its kind in West Africa, we developed high resolution spatiotemporal land use regression (LUR) models to map fine particulate matter (PM2.5) and black carbon (BC) concentrations in the Greater Accra Metropolitan Area (GAMA), one of the fastest sprawling metropolises in SSA. We conducted a one-year measurement campaign covering 146 sites and combined these data with geospatial and meteorological predictors to develop separate Harmattan and non-Harmattan season PM2.5 and BC models at 100 m resolution. The final models were selected with a forward stepwise procedure and performance was evaluated with 10-fold cross-validation. Model predictions were overlayed with the most recent census data to estimate the population distribution of exposure and socioeconomic inequalities in exposure at the census enumeration area level. The fixed effects components of the models explained 48–69 % and 63–71 % of the variance in PM2.5 and BC concentrations, respectively. Spatial variables related to road traffic and vegetation explained the most variability in the non-Harmattan models, while temporal variables were dominant in the Harmattan models. The entire GAMA population is exposed to PM2.5 levels above the World Health Organization guideline, including even the Interim Target 3 (15 μg/m3), with the highest exposures in poorer neighborhoods. The models can be used to support air pollution mitigation policies, health, and climate impact assessments. The measurement and modelling approach used in this study can be adapted to other African cities to bridge the air pollution data gap in the region.

Association between Meningococcal Meningitis and Santa Ana Winds in Children and Adolescents from Tijuana, Mexico: A Need for Vaccination.

Based on previous studies (regional and national), Tijuana, Baja California, Mexico (across the border from San Diego, California, USA), has been shown to have the highest rate of meningococcal meningitis (MeM) in the country. However, the reason for this high incidence has not yet been established. To explain this regional/endemic public health problem, we aimed to evaluate whether there is a climatic association with MeM in the region. In the "African Meningitis Belt," the Harmattan seasons are associated with MeM outbreaks; similarly, the Santa Ana winds (SAWs) seasons are characterized by hot and dry winds (similar to Harmattan seasons) that occur seasonally in Southwest California, USA, and Northwest Baja California, Mexico. We aimed to determine a potential association of SAWs with MeM in Tijuana, Baja California, Mexico, which in turn may partially explain the high rate of this disease in the region. Based on our previously published data obtained from thirteen years of active surveillance of MeM and a 65-year review showing the seasonal occurrence of SAWs, we estimated the risk ratio (RR) for the total case numbers of MeM (51 cases of children < 16 years old) vs. bacterial meningitis not caused by Neisseria meningitidis (NMeM, 30 cases, same age group) during seasons with and without SAWs. We found an association between SAWs and MeM, but not with NMeM (RR = 2.06, p = 0.02 (95% CI 1.1 to 3.8), which may partially explain the high endemicity of this deadly disease in this part of the globe. This study shows a new potential climatic association with MeM and provides more information that justifies universal meningococcal vaccination in Tijuana, Mexico.

Association of Meteorological Factors With COVID-19 During Harmattan in Nigeria.

Harmattan is a season of dry, cold, dusty wind, and haze that is peculiar to West Africa. This season and COVID-19 share common conditions such as malaise and respiratory issues like as runny nose, cough and sneezing, and raise a question of a possible relationship that begs to be answered. This study investigated whether the meteorological factors of humidity and wind speed during harmattan have association with COVID-19 incidence and mortality in the 2 major COVID-19 epicenters of Lagos state and the Federal Capital Territory (FCT) in southern and northern geopolitical regions of Nigeria respectively. Data used were from March, 2020 to February, 2022, which corresponded to the period of 2 years after the first case of COVID-19 was detected in Nigeria. Correlation analysis was performed using incidence or mortality data on COVID-19 over the duration of 2 years and during the harmattan periods, as well as the humidity and wind speed data for the corresponding periods. Our results showed that there was no significant correlation between the humidity or wind speed and COVID-19 daily incidence or mortality during the harmattan and non-harmattan periods in Lagos state. In the FCT however, there was a significant positive correlation between humidity and COVID-19 incidence, as well as a negative correlation between wind speed and COVID-19 incidence. No significant correlation existed between humidity or wind speed and daily mortality. Taken together, the findings of this study show that weather components of the harmattan season have association with COVID-19 incidence but not mortality, and the association could vary depending on location.

Seasonal Photon Output Trend from Linear Accelerator in Sokoto, North-Western Nigeria

Background: Linear accelerators are so sensitive to variability of temperature, pressure, humidity and dust; thus, weather factors can cause common errors in photon output which in turn can compromise constancy and consistency in precise delivery of tumor dose. Dose checker is such a dose-measuring devices that has an inbuilt correction factor for bunker temperature and pressure changes which ensures the photon output is within the accepted values to the patient. The aim of the study is to find the effect of seasonal changes on Linac and its influence on the patient. Methods: This is a retrospective study and daily records of 6 and 15 MV photon output with their corresponding temperature and pressure from January 2019 and December 2021 were extracted and reviewed. Precision mercury-in-glass thermometer and Barometer (OPUS 10 THI) were used to keep daily records of bunker temperature and pressure while their seasonal behaviours were recorded. Mean values of each month of the year was calculated and arranged according to three seasons of the year; results were represented in graphs, tables and bar charts. Results: The overall mean photon outputs were 0.997 and 0.828 cGy/MU for 6 and 15 MV respectively. The deviation of photon outputs from their reference values were ±2% for 6MV and ±3% for the 15MV energy. The mean bunker temperature was 27.07oC. The overall mean bunker pressure was 977.23 hpa. During harmattan season the temperature and pressure ranged between 26.8-25.4oC and 978-976.1 hpa respectively. In hot season bunker temperature was between 25.7-29.5oC and pressure was between 976.1-975.0 hpa. For the wet season, the temperature was between 29.5-25.7oC, and the corresponding bunker pressure ranged between 980.0-976.3 hpa. Conclusion: The seasons of year influenced variation in bunker temperature and pressure with corresponding seasonal photon output variation despite the use of dose checker. Low photon outputs were recorded during harmattan and hot seasons while higher outputs were recorded during wet season. Keywords: Season; Trend; Photon output, Linear Accelerator

AIR POLLUTION AND HEALTH: PARTICULATE MATTER PM2.5 MEASUREMENTS IN CANTONMENTS, GHANA

Particulate matter (PM) air pollution research has improved our understanding of major pollution sources and the quantification of their impact. Although several PM studies have been conducted in Accra, Ghana, in recent decades, few have offered an integrated knowledge of PM sources in the various sub-cities. The purpose of this study was to consolidate data and investigate additional aspects of PM investigations of Cantonments, a residential neighborhood in Ghanas capital. There is evidence of poor air quality in Accra, particularly during the dry season (Harmattan season). From December through February, a severely dry, dusty easterly or north-easterly wind sweeps over the West African coast, causing Harmattan. The PM2.5 concentrations for Cantonments for two years and the average monthly air quality indices were analysed and discussed. The results reveal the need to regularly check the daily air quality indices and curb their impacts since it has a notable health effect on the general public. KEYWORDS: PM2.5; Air pollution; Public health; Accra; Ghana

Urban land use land cover mapping in tropical savannah using Landsat-8 derived normalized difference vegetation index (NDVI) threshold

Generation of land use/land cover map at different spatial scales using satellite remote sensing data has been in practice as far back as early 1970s. Since then, research focus has been on the development of classification steps and improving the quality of the resulting maps. In recent times, the demand for detailed high accuracy land-use and land-cover (LULC) data has been on the increase due to the growing complexity of earth processes, while, at the same time, processing step is becoming more complex. This paper explores Landsat 8 derived normalized difference vegetation index (NDVI) threshold for the purpose of simplifying land cover classification process. NDVI images of January, May and December, 2018, representing dry, wet and harmattan seasons were generated. Thereafter, NDVI values corresponding to the location of a set of training data representing the target urban land covers (water, built-up area, soil, grassland and shrub) were extracted. Using the statistics of the extracted values, NDVI threshold for the respective land cover type were determined for the classification process. Finally, the classification accuracy was evaluated using the unbiased matrix coefficient technique which produced overall accuracy of 71.3%, 46.4% and 75.6% at 95% confidence limit for the months of January, May and December of the year review respectively. The result has shown that NDVI threshold is a simple and practical alternative to obtain LULC map at a reasonable time with a few data.

Prediction of personal exposure to PM2.5 in mother-child pairs in rural Ghana.

Background:Air pollution epidemiological studies usually rely on estimates of long-term exposure to air pollutants, which are difficult to ascertain. This problem is accentuated in settings where sources of personal exposure differ from those of ambient concentrations, including household air pollution environments where cooking is an important source.Objective:The objective of this study was to assess the feasibility of estimating usual exposure to PM2.5 based on short term measurements.Methods:We leveraged three types of short-term measurements from a cohort of mother-child pairs in 26 communities in rural Ghana: (A) personal exposure to PM2.5 in mothers and age four children, ambient PM2.5 concentrations (B) at the community level and (C) at a central site. Baseline models were linear mixed models with a random intercept for community or for participant. Lowest root-mean-square-error (RMSE) was used to select the best performing model.Results:We analyzed 240 community-days and 251 participant-days of PM2.5. Medians (IQR) of PM2.5 were 19.5 (36.5) μg/m3 for the central site, 28.7 (41.5) μg/m3 for the communities, 70.6 (56.9) μg/m3 for mothers, and 80.9 (74.1) μg/m3 for children. The ICCs (95% CI) for community ambient and personal exposure were 0.30 (0.17, 0.47) and 0.74 (0.65, 0.81) respectively. The sources of variability differed during the Harmattan season. Children’s daily exposure was best predicted by models that used community ambient compared to mother’s exposure as a predictor (log-scale RMSE: 0.165 vs 0.325).Conclusion:Our results support the feasibility of predicting usual personal exposure to PM2.5 using short-term measurements in settings where household air pollution is an important source of exposure. Our results also suggest that mother’s exposure may not be the best proxy for child’s exposure at age four.

The Role of Meteorological Variables and Aerosols in the Transmission of COVID-19 During Harmattan Season.

The role of atmospheric parameters and aerosols in the transmission of COVID‐19 within tropical Africa, especially during the harmattan season, has been under‐investigated in published papers. The harmattan season within the West African region is associated with significant dust incursion from the Bodele depression and biomass burning. In this study, the correlation between atmospheric parameters (temperature and humidity) and aerosols with COVID‐19 cases and fatalities within seven locations in tropical Nigeria during the harmattan period was investigated. COVID‐19 infection cases were found to be significantly positively correlated with atmospheric parameters (temperature and humidity) in the southern part of the country while the number of fatalities showed weaker significant correlation with particulate matters only in three locations. The significant correlation values were found to be between 0.22 and 0.48 for particulate matter and −0.19 to −0.32 for atmospheric parameters. Although, temperature and humidity showed negative correlations in some locations, the impact is smaller compared to particulate matter. In December, COVID‐19 cases in all locations showed strong correlation with particulate matter except in Kano State. It is suggested that a reduction in atmospheric particulate matter can be used as a control measure for the spread of COVID‐19.

Inferring iron-oxide species content in atmospheric mineral dust from DSCOVR EPIC observations

Abstract. The iron-oxide content of dust in the atmosphere and most notably its apportionment between hematite (α-Fe2O3) and goethite (α-FeOOH) are key determinants in quantifying dust's light absorption, its top of atmosphere ultraviolet (UV) radiances used for dust monitoring, and ultimately shortwave dust direct radiative effects (DREs). Hematite and goethite column mass concentrations and iron-oxide mass fractions of total dust mass concentration were retrieved from the Deep Space Climate Observatory (DSCOVR) Earth Polychromatic Imaging Camera (EPIC) measurements in the ultraviolet–visible (UV–Vis) channels. The retrievals were performed for dust-identified aerosol plumes over land using aerosol optical depth (AOD) and the spectral imaginary refractive index provided by the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm over six continental regions (North America, North Africa, West Asia, Central Asia, East Asia, and Australia). The dust particles are represented as an internal mixture of non-absorbing host and absorbing hematite and goethite. We use the Maxwell Garnett effective medium approximation with carefully selected complex refractive indices of hematite and goethite that produce mass fractions of iron-oxide species consistent with in situ values found in the literature to derive the hematite and goethite volumetric/mass concentrations from MAIAC EPIC products. We compared the retrieved hematite and goethite concentrations with in situ dust aerosol mineralogical content measurements, as well as with published data. Our data display variations within the published range of hematite, goethite, and iron-oxide mass fractions for pure-mineral-dust cases. A specific analysis is presented for 15 sites over the main dust-source regions. Sites in the central Sahara, Sahel, and Middle East exhibit a greater temporal variability of iron oxides relative to other sites. The Niger site (13.52∘ N, 2.63∘ E) is dominated by goethite over the Harmattan season with a median of ∼ 2 weight percentage (wt %) of iron oxide. The Saudi Arabia site (27.49∘ N, 41.98∘ E) over the Middle East also exhibited a surge of goethite content with the beginning of the shamal season. The Sahel dust is richer in iron oxide than Saharan and northern China dust except in summer. The Bodélé Depression area shows a distinctively lower iron-oxide concentration (∼ 1 wt %) throughout the year. Finally, we show that EPIC data allow the constraining of the hematite refractive index. Specifically, we select 5 out of 13 different hematite refractive indices that are widely variable in published laboratory studies by constraining the iron-oxide mass ratio to the known measured values. The provided climatology of hematite and goethite mass fractions across the main dust regions of Earth will be useful for dust shortwave DRE studies and climate modeling.

Effect of Dust Accumulation on the Performances of Solar Panels in Static and Tracking Systems in Bauchi Metropolis of Nigeria

The research aimed at comparing the effect of dust accumulation on the performances of solar PV modules in static position and on a tracking system within Bauchi metropolis of Nigeria , during the harmattan season –November to December. Dust deposition on the surface of PV panel reduces the conversion efficiency by absorbing and preventing the Solar radiation from reaching the cells of the panel. This necessitated the need to develop a reliable tool to relate energy production from solar cells with respect to dust deposition on both static and solar tracking PV modules. A test bed was designed for the field measurement of output current, voltage, temperature and dust weight data from the two PV modules.” Centsys” polycrystalline solarpanels () was used for the research. A statistical technique involving regression analysis in SPSS software was used to correlate between the various measured data from the test bed to predict the effect of dust accumulation on the surface of each module, which will enable solar power installers to take necessary measures for improving the PV module’s conversion efficiency during the period under review. The research result showed that the effect of dust on the tracking solar PV moduleis less significant compared to the static panel, giving the former a better conversion efficiency.

TRNSYS 16: A veritable solar modelling and programming simulation tool used in the design of a continuous solar powered adsorption refrigeration system

Project feasibility gave rise to the need for simulation. Simulation of a project leads to reduction in production cost, which ensures the success of the proposed project. Also, it provides initial design data for the experimental project. Thus, the design analysis and variables used for project simulation must be designed properly, revised, tested, and re-tested to guarantee how accurate the experimental design is. Hence, solar adsorption refrigeration system was designed, simulated and constructed using zeolite 4A/13X blend and water. The models were simulated using TRNSYS 16.0 simulation tool. From the result, it was observed that the collector area increases with increase in the system COP from month to month. The highest system COP of 1.53 was obtained in the month of April while the least was 0.4 for July due to frequent rainfall. Also, a much high COP was obtained for dry season while lower COP was gotten for harmattan season. Key words: TRNSYS, adsorption refrigeration, solar cooling, solar adsorption, adsorbent, solar concentrating collectors.

Assessment of atmospheric and soil water stress impact on a tropical crop: the case of Theobroma cacao under Harmattan conditions in eastern Ghana.

In West Africa, Harmattan-induced atmospheric and soil droughts represent seasonally recurring hazards for Theobroma cacao L. agro-ecosystems. Under the influence of the Harmattan winds, precipitation is impaired and air humidity and temperature reach stressful levels. Climate change is causing an increase in temperature that will drive up the evaporative power of the atmosphere, risking to harshen both the soil and atmospheric stress. This would further threaten the viability of cacao cultivation in this region. To characterize the response of cacao trees to atmospheric and soil drought, we monitored two sub-plots, with and without irrigation, throughout one Harmattan season (November 2019 - March 2020) in the Eastern region in Ghana. For both treatments we recorded: sap flow velocity, photosynthetic active radiation (PAR) above and below the canopy, soil moisture, temperature, air humidity and daily precipitation. Leaf area index (LAI) was estimated from PAR measurements. To characterize drought responses of mature cocoa trees during the day and at the seasonal scale, we developed two boosted regression trees models (BRT) with the environmental variables measured. The atmospheric component of Harmattan-induced drought was found to affect the canopy to a similar extent as soil water stress, both causing a decline in LAI of 33%. This study confirmed the importance of soil drought but highlighted as well the crucial role of atmospheric drought for this species’ transpiration control. Soil and atmospheric water stresses did not have a synergistic effect on transpiration under the studied conditions. The BRT models identified LAI as one of the most influential drivers for sap velocity, which, in turn was sensitive to the interactive effect of both atmospheric and soil drought. Our results highlight that not only reduced precipitation but also increasing atmospheric drought is likely to negatively impact on cacao production in West Africa under increasingly dry conditions imposed by the influence of the Harmattan winds.