Desert Wind Research Articles

Downscaling and Wind Resource Assessment of Climatic Wind Speed Data Based on Deep Learning: A Case Study of the Tengger Desert Wind Farm

Analyzing historical and reanalysis datasets for wind energy climatic characteristics offers crucial insights for wind farms and short-term electricity generation forecasting. However, large-scale wind farms in Chinese deserts, the Gobi, and barren areas often lack sufficient wind measurement data, leading to challenges in assessing long-term power generation revenue and introducing uncertainty. This study focuses on the Tengger Desert as the study area, processes the Coupled Model Intercomparison Project Phase 6 (CMIP6) data, and analyzes and compares wind energy’s future characteristics utilizing a developed deep learning (DL) downscaling algorithm. The findings indicate that (1) the Convolutional Neural Network (CNN) downscaling model, with the Weather Research and Forecasting Model (WRF) numerical simulation results as the targets, exhibits spatial distribution consistency with WRF simulation results in the experimental area. (2) Through testing and validation with three practical wind measurements, the annual average wind speed error is below 4%. (3) In the mid-term future (~2050), the average wind speed in the experimental area remains stable with a multi-year average of approximately 7.00 m·s−1. The overall wind speed distribution range is significant, meeting the requirements for wind farm development.

Effect of sand and crosswind on the performance of solar chimney power plant

AbstractA solar chimney power plant (SCPP) is suitable to be deployed in desert areas, but there are few studies on the impact of desert wind and sand. In this paper, numerical simulations for the Spanish prototype SCPP were conducted to investigate desert environmental parameters, including sand movement, crosswind, and sand deposition, on the output performance of SCPP. The results indicate that the main erosion area of the turbine blade in the SCPP is the leading edge of the blade pressure surface. The erosion area of the suction surface is much less than that of the pressure surface, mainly concentrated on the leading edge. The output power of SCPP is reduced by 73.3% because of the crosswind and it decreases by 16.9% after the windbreak wall is installed. The sand and dust deposition would affect the transmissivity of the solar radiation through the collector cover. In a dusty environment for 1 month, the system output power decreased by 12.9%, and the collector efficiency decreased from 34% to 23% due to the sand deposition. These results show that the sand has a considerable negative effect on the performance of SCPP in ways of sand erosion and deposition. Sand removal is necessary for SCPP.

Soiling Modelling in Large Grid-Connected PV Plants for Cleaning Optimization

Soiling of PV modules is an issue causing non-negligible losses on PV power plants, between 3 and 4% of the total energy production. Cleaning is the most common way to mitigate soiling. The impact of the cleaning activity can be significant, both in terms of cost and resources consumption. For these reasons, it is important to monitor and predict soiling profiles and establish an optimal cleaning schedule. Especially in locations where raining is irregular or where desert winds carry a high concentration of particles, it is also important to know how precipitation and dust events affect the soiling ratio. This paper presents a new model based on environmental conditions that helps the decision-making process of the cleaning schedule. The model was validated by the analysis of five large grid-connected PV plants in Spain over two years of operation, with a total power of 200 MW. The comparison between the model and soiling sensors at the five locations was included. Excellent results were achieved, the mean difference between sensors and model being 0.71%.

Heterogeneous warming impacts of desert wind farms on land surface temperature and their potential drivers in Northern China

To address rapid climate change, wind energy has been widely developed in China in the last two decades. However, wind farm (WF) turbulence effects can change the local climate by redistributing temperature, humidity, and heat fluxes. Previous studies indicate that WFs can significantly increase nighttime land surface temperature (LST); however, their conclusions are mainly derived from individual WFs and ignore heterogeneous impacts among multi-WFs in China. Another large source of uncertainty is that the WFs used in previous studies are mainly located in croplands or grasslands, which may obscure direct WF impacts because of the interactions between vegetation and the atmosphere. In this study, we detect impacts with MODIS LST products during 2001–2018 at sixteen WFs in the desert of northern China. The results suggest that the averaged warming impacts of WFs on LST are similar between nighttime (0.237 °C) and daytime (0.250 °C). However, the uncertainty is much greater for daytime (SD = 0.519 °C) than for nighttime (SD = 0.146 °C) due to spatially heterogeneous impacts of desert WFs on LST. Optimal structural equation models suggest that wind speed, precipitation, and distribution patterns of wind turbines mainly explain the spatial heterogeneity of the desert WF impacts on nighttime LST. Given the rapid development of WFs globally, the local warming impacts of WFs and their corresponding mechanisms should be highlighted as a high priority in the fields of energy and climate.

Noctiluca blooms intensify when northwesterly winds complement northeasterlies in the northern Arabian Sea: Possible implications

Wind systems are known as nutrient sources playing significant roles in the oceanic realm and global climate oscillations. This study explores, for the first time, the effect of winds on the winter blooms of the mixotrophic dinoflagellate, the green variant of Noctiluca scintillans (NSG) in the northern Arabian Sea. When the NSG abundance was lower (i.e., <∼10000 cells l−1), it was coupled to silicic acid (H4SiO4), on which diatoms (phytoplankton) in turn depended. At higher abundance (i.e., NSG>∼10000 cells l−1), H4SiO4 and H4SiO4:DIN (dissolved inorganic nitrogen) ratio fell. The NSG was then intensely green and chlorophyll-a richer, attributed to a change in the mode of NSG's nutrition from heterotrophy to autotrophy-dominance. The back-trajectory model revealed that the winds were mostly northeasterly (NE) initially (during February) and were north-westerly (NW) towards the end of winter (March). Separately for the NE and NW winds, the NSG abundance was 10655±18628 and 28896±46225 cells l−1, respectively. The H4SiO4:DIN ratio correspondingly reached <0.2 and ≥0.4. The NSG was modelled with high significance (p<0.001, N=33) versus the NE and NW wind speeds. Thus, while the NE winds deepened the mixed layer and caused nutrient enrichment and phytoplankton production, the NW winds facilitated the recovery of the H4SiO4:DIN ratio and economical use of H4SiO4 for phytoplankton production. It is hypothesized that this process is helped by iron input from NW desert winds during the latter part of winter when the NSG blooms intensify.

Solar passive system design for sustainable building at Jodhpur City

Buildings in India need both heating and cooling due to the country's diverse climate, which necessitates heating in high elevations and hilly areas and cooling in lower elevations and desert parts. Jodhpur region in Rajasthan has influence of strong desert winds and hot -dry climate throughout the year therefore it is essential to provide a sustainable method for thermal comfort energy conservation and temperature equilibrium are two important parameter in such cases, here we attempt to provide a design where favorable orientation, air gap in roof for insulation, reflective external finishes and proper use of sun light with constructive positing of window in direction of cool winds and complimentary as regards to solar radiation could be made available. The buildings in Jodhpur are rather pleasant inside due to the big roofs and walls that would provide thermal dampening. The fact that the inside temperatures are identical towards the outside air temperature demonstrates the efficacy of the natural cooling technologies employed in Jodhpur. Jodhpur's interior temperatures are on the approach of becoming bearable. Because the average outside temperature exceeds in some areas with higher relative humidity, even with good building design, ideal inside circumstances may not be possible. It's important in these situations to maintain the average interior temperature less than the outside temperature. To deflect the scorching winds, specially constructed mud walls are still common in the hamlets of western Rajasthan. In hot and dry climates, these were among the most common passive cooling strategies. Solar passive architecture ensures that fenestration, such as doors and windows, are appropriately positioned and built to benefit from the sun and wind. The objective of heating is to let as much of the sun's energy in as possible while minimizing nighttime heat loss. Windows, therm-walls, solariums, and other similar ways provide direct gain.

Tracking Airborne Pollution with Environmental Magnetism in A Medium-Sized African City

As in other parts of the world, air pollution over West and Central Africa has major health and meteorological impacts. Air quality assessment and its possible sanitary impact have become essential even in medium-sized towns, therefore amplifying the need for easy-to-implement monitoring methods with low environmental impact. We present here the potential of magnetic methods to monitor air quality at street level in the medium-sized city of Maroua (northern Cameroon) affected by dust-laden desert winds. More than five hundred (544) samples of bark and leaves taken from Neem trees in Maroua were analyzed. Magnetic susceptibility, saturation remanence, and S-ratio were found to determine the concentration and nature of magnetic particles. They are dominated by magnetite-like particle signals as a part of particulate emissions due to urban activities, including both traffic, composed of a substantial proportion of motorcycles, and wood burning for food preparation. We show that both bark and leaves from Neem trees are adequate passive bio-recorders. The use of both enables different times and heights to be sampled, allowing for the high-resolution monitoring, in terms of spatialization, of various urban environments. Particle emissions require assessment and screening that could be carried out rapidly and efficiently by magnetic methods on bio-recorders, even in cities impacted by dust-laden wind.

Migraine Triggers: An Overview of the Pharmacology, Biochemistry, Atmospherics, and Their Effects on Neural Networks.

We define a migraine trigger to be an endogenous agent or agency such as the menses or an exogenous agent or agency such as red wine or a drop in barometric pressure, and their ability to reduce the threshold of a migraine attack in those predisposed to migraine. This definition excludes agents with idiosyncratic mechanisms that may trigger a migrainous (migraine-like) headache in non-migraineurs such as benign cough headaches or headaches due to altitude-sickness. We also assume as axiomatic that migraine has as its basis the activation of the trigeminovascular pathway (TVP) and the key role of serotonin and the calcitonin gene-related peptide (CGRP). The network activation of the visual/auditory association cortices and the rostrodorsal pons (locus ceruleus and raphe nucleus) are also accepted as key features of activation of the TVP. In addition, we outline the role of the superior salivatory nucleus-sphenopalatine ganglion-greater superficial petrosal nerve (SSN-SPG-GSPN) arc in migraine activation.We also explore how olfactory afferents intermingle with trigeminal nerve collaterals in the glomeruli of the olfactory bulb thus allowing volatile molecules to activate the TVP and induce a migraine. The classification of migraine triggers is complex, as there is a wide panorama of inciting agents, including atmospheric conditions, a wide-ranging variety of foods and beverages, endogenous hormonal influences, synthetic alkaloids and dyes, and volatile molecules (odorants). We will explore the high-frequency migraine-provoking agents in each category. There are exciting and intriguing hypotheses regarding the role of atmospheric chemistry when the barometric pressure drops; the role of hot, dry desert winds and lightning discharges in the generation of cations and the turnover of serotonin in the nervous system. We will explore the effects of a drop in barometric pressure on the vestibular nuclei and the modulation of sympathetically mediated pain. The role of volatile odorants and their activation of the transient receptor potential ankyrin-1 (TRPA-1) receptor will be outlined. We will streamline the highly complex role of estrogen fluctuation in the precipitation of migraine headaches, its pharmacodynamic effects, and the role of the sexually dimorphic nucleus of the preoptic area (SDN-POA) of the hypothalamus. We will also adumbrate the protean effects of alcohol and its congeners and the role of stress and sleep disturbances in the allostatic load model of salience network-pain perception.

Applying porous trees as a windbreak to lower desert dust concentration: Case study of an urban community in Dubai

Windbreaks are rows of rough or porous materials that create aerodynamic shelter from wind or purify the wind. The aim of this study was to investigate the role of adding windbreaks of permeable trees in order to achieve a more comfortable microclimate and healthy atmosphere at an urban level. A local community in Dubai was chosen to act as a case study for this project. The case was analyzed before and after applying permeable trees as a windbreak to purify the desert wind, using different scenarios for one year. Readings of PM₁₀ were recorded for one year and the effect of windbreaks was quantified by calculating the concentration in front of and behind the windbreak using SimScale software. Two cases were investigated over the period of one year: 20 m spacing (case 1) and 10 m spacing between trees (case 2). Wind velocity and pressure were also measured. The analysis shows that case 1 was more effective than case 2 when designing a windbreak in a dusty area. The tree windbreak was more effective if the wind was prevailing perpendicularly. In case 2, the dust reduction ranged between 19 % and 22 %. The paper reveals more critical findings.

Cryospheric processes in Quaternary and Cretaceous hyper‐arid plateau desert oases

AbstractWinter supercooling of oasis waters in hyper‐arid plateau deserts leads to the formation of ice floes on oases water surfaces. Multi‐year satellite imagery from recent oases in the Badain Jaran Desert (China) reveals dynamic cryospheric processes including ice floe, ice jams abutting on border ice, hinge and transverse cracks, multiple ice lobes related to aufeis formation on the ice floe surface indicating oases water level oscillations linked with short‐term variations of the groundwater input. Oasis ice floe break up and transportation by strong desert winds produce an effective gouge and abrasion mechanism of oasis margin sediments, incorporating them both into the oasis bottom, and as supra‐ice floe debris that ultimately will be released to the bottom of the oasis as dropstones as the ice cover melts. Supercooling conditions in the Badain Jarain Desert oases suggest that anchor ice can form in the oases bottoms from fazil ice crystals generated in open supercooled oasis waters. Mud dropstones and diamicton in Cretaceous wet interdune facies from China suggest ice‐rafting processes in oases. Rounded and subangular mud intraclasts are mud boudins formed by in situ boudinage of mud interdune sediments due to the combined effect of compaction by prograding aeolian sediments and aufeis formation. Anchor ice formed in the oases bottoms lifted them up due to floatability and released them as dropstones to the oasis bottom when melted. Cryospheric processes in hyper‐arid oases are more active than expected and may play a significant role in intraclast reworking. The recognition of these processes is critical for Mesozoic palaeoclimates.

Urban Overheating and Cooling Potential in Australia: An Evidence-Based Review

Cities in Australia are experiencing unprecedented levels of urban overheating, which has caused a significant impact on the country’s socioeconomic environment. This article provides a comprehensive review on urban overheating, its impact on health, energy, economy, and the heat mitigation potential of a series of strategies in Australia. Existing studies show that the average urban heat island (UHI) intensity ranges from 1.0 °C to 13.0 °C. The magnitude of urban overheating phenomenon in Australia is determined by a combination of UHI effects and dualistic atmospheric circulation systems (cool sea breeze and hot desert winds). The strong relation between multiple characteristics contribute to dramatic fluctuations and high spatiotemporal variabilities in urban overheating. In addition, urban overheating contributes to serious impacts on human health, energy costs, thermal comfort, labour productivity, and social behaviour. Evidence suggest that cool materials, green roofs, vertical gardens, urban greenery, and water-based technologies can significantly alleviate the UHI effect, cool the ambient air, and create thermally balanced cities. Urban greenery, especially trees, has a high potential for mitigation. Trees and hedges can reduce the average maximum UHI by 1.0 °C. The average maximum mitigation performance values of green roofs and green walls are 0.2 °C and 0.1 °C, respectively. Reflective roofs and pavements can reduce the average maximum UHI by 0.3 °C. In dry areas, water has a high cooling potential. The average maximum cooling potential using only one technology is 0.4 °C. When two or more technologies are used at the same time, the average maximum UHI drop is 1.5 °C. The mitigation strategies identified in this article can help the governments and other stakeholders manage urban heating in the natural and built environment, and save health, energy, and economic costs.

Hospitalidad y resistencia de las lenguas nómadas

The title of the present essay crystallized as a "desert rose" from the minerals of a review of the recently published book De nomadismos y hospitalidades Comcaac y Saharauis. Inspired by its paths and textures, it reflects on fundamental nomadism in all languages, nomadism that –like the people who practice it teach us– is based on hospitality and resistance. This essay is a poetic exercise that reaches the spaces of politics and the philosophy of language, and that caresses and chafes them like the desert wind carves the figures it names and the human faces which express them.

Cholla cactus frames as lightweight and torsionally tough biological materials

Biological materials tested in compression, tension, and impact inspire designs for strong and tough materials, but torsion is a relatively neglected loading mode. The wood skeletons of cholla cacti, subject to spartan desert conditions and hurricane force winds, provide a new template for torsionally resilient biological materials. Novel mesostructural characterization methods of laser-scanning and photogrammetry are used alongside traditional optical microscopy, scanning electron microscopy, and micro-computed tomography to identify mechanisms responsible for torsional resistance. These methods, in combination with finite element analysis reveal how cholla meso and macro-porosity and fibril orientation contribute to highly density-efficient mechanical behavior. Selective lignification and macroscopic tubercle pore geometry contribute to density-efficient shear stiffness, while mesoscopic wood fiber straightening, delamination, pore collapse, and fiber pullout provide extrinsic toughening mechanisms. These energy absorbing mechanisms are enabled by the hydrated material level properties. Together, these hierarchical behaviors allow the cholla to far exceed bamboo and trabecular bone in its ability to combine specific torsional stiffness, strength, and toughness. Statement of SignificanceThe Cholla cactus experiences, due to the high velocity desert winds, high torsional loads. Our study has revealed the amazingly ingenious strategy by which the tubular structure containing arrays of voids intermeshed with wood fibers resists these high loads. Deformation is governed by compressive and tensile stresses which are greatest at 45 degrees to the cross section. It proceeds by stretching, sliding, and bending of the wood fibers which are coupled with the pore collapse, resulting in delayed failure and a high torsional toughness.

The Airplane Boneyard Studio: Considering Stillness and Creative Practice from an Airplane Wing

In 1975, Australian artist Ian Howard taped sheets of paper to the nose of the Enola Gay, and through rubbing the surface with a thin layer of wax crayon, he created a ghost-like impression of the airplane that dropped an atomic bomb on Hiroshima. Forty years later, in an aircraft boneyard in Arizona, I placed redundant maps of the Great Sandy Desert on the wing of a passenger jet to take an imprint of a similarly disused yet functionally different aircraft. Despite the conceptual and temporal differences that separated these two acts, the process of rubbing—or frottage—resulted in two artworks that revealed traces of the physical encounter with the aircraft surfaces, the dynamic handling of the materials of making, and the practical and aesthetic impact of working in the field. By its very nature of proximity and touch, the process of frottage records a bodily engagement with both object and environment. Recounting the experiences of working on the wing of a civilian plane in the desert heat of Arizona forty years after Howard worked on the Enola Gay, I reflect on the low-tech process of frottage and its capacity to suggest our respective embodied experiences of making. Furthermore, I suggest that traces of environmental factors such as high humidity, desert winds, or extreme heat, or time-based factors such as limited access to stationary airplanes can be captured and archived through creative practice as a way to contribute to contemporary understandings of mobility and its counterpart stillness.

Formation and paleoenvironment of rhizoliths of Shiyang River Basin, Tengeri Desert, NW China

Rhizoliths found in bed of the late Quaternary paleolake Zhuyezhe, Minqin Basin, central Tengeri Desert, NW China were studied. Vegetation coverage is present at some locations in the paleolake area although, much of the bed area is covered with moving dunes. Rhizoliths are occasionally eroded out and exposed to the air. The morphology of the rhizoliths resembles singular or branching carbonated tubules which are hollow in their central part. The rhizoliths are black to grey, and are broken and scattered randomly on the sand surface of the lake bed. The lacustrine deposits are black greenish silt or silty clay with a large quantity of white petite lake snail shells. The possible plant types, sources and formation conditions of carbon dioxide and calcium, the sedimentary and diagenetic environments, and the process of rhizolith formation were discussed via examining rhizoliths macromorphology, studying the micromorphology and mineralogy by microscopy, cathodoluminescence and scanning electron microscope, and studying the chemical compositions of cementing minerals and fragments by energy dispersive X-ray spectra. The original roots of the rhizoliths belong to hydrophytes, such as Typha latifolia, Scirpus maritimus and Carex stenophylla. Lake snails and previous pollen data indicate that the rhizoliths formed in a sedimentary environment of shallow fresh water lake like marginal or palustrine areas during the Holocene. Shallow lake water disturbance by desert wind above the loose sandy sediment or soil was favoring the rhizoliths formation. A continuous supply of oxygen through water disturbance led to complete oxidation of roots and producing carbon dioxide. Dissolution of CO2 in water and so, carbonic acid production resulted in minerals weathering such as feldspar and primary carbonate particles and the release of K+ and Ca2+ ions. At presence of CO2 and Ca2+ saturated in the pore water around the roots of hydrophytes within the sediments or soil, carbonate precipitation occurred around the root channel and led to rhizoliths formation as tubules. The petrifaction process therefore, has happened in margin of the paleolake with shallow water and weak redox condition, which implies the suitability of rhizolith for reconstructing paleoenvironment.

Disturbance affects biotic community composition at desert wind farms

Context The global benefits of increased renewable energy production may come at a cost to local biotic communities and even regional ecosystems. Wind energy developments, in particular, are known to cause bird and bat mortalities, and to fragment habitat for terrestrial vertebrates within developed project areas. Effects on species sensitive to wind turbines (and increased prevalence of species tolerant to this disturbance) might alter community-level patterns of occurrence, with potentially detrimental changes to wildlife habitat and ecosystem health. Aims The present study assessed whether wind energy developments produced downstream ecological costs. Specifically, community composition and diversity were compared between wind farms and nearby areas without energy development. Methods Traditional diversity measures and non-metric multidimensional scaling (NMDS) were used to map ecological dissimilarity across four wind farms and five reference (control) areas in Southern California, USA. Key results Wind farms had more noise and road disturbance than sites without turbine installations. Noise and disturbance were correlated with reduced plant richness, particularly for endemic plant species and, conversely, with increased non-native plant richness. Animal communities at wind farms were less diverse, with fewer species and lower evenness relative to reference areas with minor or no disturbances. Wind farms had fewer rare and unique species and, for some species of avian predators, encounter rates were lower at wind farms. Conclusions Renewable wind energy may indeed cause shifts in local communities. Although wind farms still supported many of the same species found in natural areas, suggesting that renewable wind energy facilities can provide useable habitat for some wildlife, these communities were also less rich and diverse. Implications Non-native species were more prevalent at wind farms, which may then facilitate further invasions into surrounding habitats. In addition, reduced overall plant and predator diversity at wind farms, and lower encounter rates for specific taxa (particular birds), may significantly affect community structure and function.

The Study of Sand-blocking Characteristic and Flow Field Simulation Analysis of the Ring-shaped Sand-barrier

Aiming at the complexity of wind direction and irregular sand flow in a desert area, a combinatorial ring-shaped sand barrier is used. Stokes law of inertia force and centrifugal force and gravity sedimentation are used. With CFD fluid software Fluent, laminar flow model Equation and κ-ε turbulence model, the wind speed of the sand in the sand-gas-solid two-phase flow passing through the circular sand barrier is studied at different distances and different altitudes after the sand barrier, the wind speeds before and after the sand barrier are compared and analyzed . The mean minimum wind speed behind the single sand barrier was reduced by 32.5% -49.4% compared with that before the sand barrier. The wind speed at different height of the composite sand barrier was reduced by 30% -58.3% compared with the inlet wind speed, which solved the problem of irregular wind and sand control in the desert wind direction.

Thermal Regime Effect on Gas-Transport Lines in the Persian Gulf

Summary Sea lines transporting gas toward the north (Iran) and south (Qatar and Saudi Arabia) and originating from fields located in the central parts of the Persian Gulf exhibit different thermal regimes. The lowest reported arrival temperatures of the gas were 18 and 11°C for the sea lines transporting gas to the northern and southern shores, respectively. The difference between the two is significant and could radically alter the hydrate-mitigation strategy and the associated economics. Metocean data reported in this study and from previous studies (Appendix A) show that the northern part of the Persian Gulf, which is also deeper, attains a well-mixed state during winter months. During this phase, the arrival temperature of the gas for South Pars (SP) sea lines decreases steadily and goes through a minimum at approximately the middle of February every year. In the southern region, the sea is shallow and water is more saline. Sinking of saline water when exposed to cool and dry ambient winter conditions is probably responsible for the reported abrupt decrease in arrival temperatures in the case of the Karan gas line. The immediate recovery of the same may be caused by the local wind/tide conditions. The likely origins of the observed lowest temperatures in the north and south regions are Arctic winds of short duration and desert winds of fairly long duration, respectively. This study summarizes hydrate-inhibition practices for these sea lines, and indicates a possibility of using the sea lines as “indirect thermometers” to provide important physical oceanographic data for long terms in a limited but economical way with fewer interruptions.

Staging the Silk Road Journey Abroad: The Case of Dunhuang Performative Arts

Staging the Silk Road Journey Abroad: The Case of Dunhuang Performative Arts

Ethical challenge of desertification in Northern Nigeria

Desertification is an urgent environmental problem that is faced by Northern Nigeria. As an environmental problem it creates a lot of challenges for the human community. These challenges include: conflicts over grazing lands and farmlands, pollution of water sources and the air by encroaching desert wind and sand, internal displacement of people, force migration of people, destruction of human lives and properties, and so on. If desertification is not stopped it impedes development and sustainability. This paper uses a critical analytic method, to examine the ethical challenges that desertification poses. It makes a conceptual analysis of the main concepts such as ethics, desertification and Northern Nigeria. It looks at how desertification is an ethical issue. The paper finds and concludes that if desertification is curbed through tree planting, and other ethical consciousness raising that leads to other practical actions, it will save both human and natural environment in Northern Nigeria.