Al Khali Desert Research Articles

Using Texture Statistics to Identify and Map Different Dune Types within the Rub’ al Khali

Understanding the movement, direction, and shape of sand dunes can contribute to reducing their impact on infrastructure and the environment. The Rub’ al Khali desert has a distribution of dune types. This study aims to identify and map the different types of dunes within the Rub’ al Khali using a texture analysis method based on a digital elevation model (DEM). Statistical texture analysis methods (variance, skewness, and kurtosis) show three different textures of sand dune shapes, according to the geography of the dunes, using data contained in global DEMs. The analysis presented in this study focused on the use of DEMs to investigate the varied dune morphology within the Rub’ al Khali. The GMTED2010 and EarthEnv_DEM90 digital elevation models were compared. Spatial variability in dune height, spatial variability in dune texture, and profile graphs were created to examine dune surfaces in cross-section. The results provided six different dune types within the sand sea: giant compound linear dunes, simple linear dunes, simple transverse dunes, compound crescentic dunes (megabarchans), huge star dunes, and many transitional forms that defy classification. The results showed that the compound linear dune and simple linear dune were the dominant dune types, covering 41.61% and 31.7% of the total study area, respectively. The maps of variance, using either 10 × 10 and 30 × 30 focal blocks, produced a fairly sharp distinction in dune texture. It is hoped that future research in aeolian geomorphology will greatly benefit from these results, which could easily be expanded with the use of more sophisticated pattern recognition software, which clearly shows the value of using such an approach.

Bronze age stone flaking at Saruq al-Hadid, Dubai, southeastern Arabia.

Excavations at Saruq al-Hadid, Dubai, UAE, discovered a stone tool technology with backed microliths dating to the Wadi Suq period and Late Bronze Age (ca. 1750–1300 BCE). The stone technology is a contemporary with metal production in the region, and the assemblage was recovered from a thick bone midden deposit at this multi-period site on the edge of the Rub’ al-Khali Desert. Small cobbles of chert were imported to the site and were reduced into flakes by hard-hammer percussion. Cores were frequently rotated during knapping and the reduction strategy was ad hoc, lacking hierarchical reduction stages. Flake tools were used as-is or modified by retouching. Some flakes were selected for backing into geometric microliths, and backing techniques often reflected high levels of stoneworking skill to produce stylised scalene shapes. A review of contemporary archaeological evidence, and the context of the Saruq al-Hadid assemblage, suggest that microliths may have been made as stone armatures for arrows despite the contemporary use of copper-based arrowheads.

Calculation of the Rub’ al Khali Sand Dune Volume for Estimating Potential Sand Sources

The Rub’ al Khali desert (or Empty Quarter) is the largest and perhaps most significant sand sea in the world. Located on the southern Arabian Peninsula, the dune field has remained largely unexplored owing to the harsh clime and difficult terrain. This study takes advantage of geospatial technology (interpolations, supervised classification, minimum focal statistic) to extract information from the data contained in global Digital Elevation Model (DEM)s, satellite imagery. The main objective here is to identify and map different dune forms within the sand sea, estimate the volume of sand and explore probable sources of sand. The analysis of dune color strongly suggests that the sand is not completely reworked and intermixed. If this is true, a spatial variability map of the mineral composition of the sand could be very revealing. The red sand is quite pronounced, the largest volume of sand (~36%) is associated with the yellow color class. Yellow sand covers most of the western part of the dunes field and seems to be a transitional color between red and white sand in the eastern part of the dune field. This suggests that the yellow sand might be derived from both local and regional sources, or it might be less oxidized, reworked, or have a different composition that represents a combination of red and white sand.

Prediction of Solar Irradiance over the Arabian Peninsula: Satellite Data, Radiative Transfer Model, and Machine Learning Integration Approach

Data from a moderate resolution imaging spectroradiometer instrument onboard the Terra satellite along with a radiative transfer model and a machine learning technique were integrated to predict direct solar irradiance on a horizontal surface over the Arabian Peninsula (AP). In preparation for building appropriate residual network (ResNet) prediction models, we conducted some exploratory data analysis (EDA) and came to some conclusions. We noted that aerosols in the atmosphere correlate with solar irradiance in the eastern region of the AP, especially near the coastlines of the Arabian Gulf and the Sea of Oman. We also found low solar irradiance during March 2016 and March 2017 in the central (~20% less) and eastern regions (~15% less) of the AP, which could be attributed to the high frequency of dust events during those months. Compared to other locations in the AP, high solar irradiance was recorded in the Rub Al Khali desert during winter and spring. The effect of major dust outbreaks over the AP during March 2009 and March 2012 was also noted. The EDA indicated a correlation between high aerosol loading and a decrease in solar irradiance. The analysis showed that the Rub Al Khali desert is one of the best locations in the AP to harvest solar radiation. The analysis also showed the ResNet prediction model achieves high test accuracy scores, indicated by a mean absolute error of ~0.02, a mean squared error of ~0.005, and an R2 of 0.99.

Neolithic long-distance exchanges in Southern Arabia: A supposed road for the ‘Jade’ axes

This paper discusses the results of a new geo-archaeological study on the nephrite (jade) axes discovered in southern Oman (Dhofar Governorate). The research presents a first account of the geological composition and the morphological structure of such tools and it outlines a preliminary distribution network of jade axe-heads across Southern Arabia. After the discovery of the first analysed sample at Shaqat Jadailah SQJ-3, in the Rub’ al-Khali Desert (Dhofar), four other archaeological axe-adze samples collected from southern Oman, were analysed using micro-Raman Spectroscopy and Energy Dispersive X-Ray Fluorescence (ED-XRF). We compared the analysed samples to other nephrite axes collected in the first pioneering exploration of Gertrude Caton-Thompson (Yemen) and Wilfred Thesiger (South Oman). These objects were then correlated with nephrite raw material from the basement exposures in Yemen. Available data show that the raw material originating in Yemen reached the Neolithic groups of Southern Rub’ al-Khali and coastal Dhofar most likely during the 6th-5th millennium BC, following a similar path to the obsidian route. The colour, texture and composition, together with the presence of other classes of lithic artefacts such as the trihedral projectile points, indicate that during this period Southern Oman was fully integrated into long-distance exchange networks. The analysis of the collected samples show that they are made exclusively from nephrite, and not from other general “green stones”. Considering the high hardness and toughness of the nephrite, this fact allows the hypothesis of a deliberate choice in the selection of raw material for its durability or prestige value.

Seasonal changes and migration of longitudinal dunes in the northeastern Rub'al Khali Desert

The morphology of small longitudinal dunes responded clearly to wind fields in the northeastern Rub'al Khali Desert. Based on local meteorological data and high-resolution satellite images, we analyzed the wind regime, drift potential (DP), dune morphology changes, and migration rates. The wind roses revealed that two opposing winds (from the northwest and southeast), both at an oblique angle to the dune crest, dominated the structure of the wind regime, with periodic changes between these directions. The annual DP from 2017 to 2019 ranged from 615 to 688 vector units (VU), and the resultant drift potential (RDP) ranged from 149 to 311 VU, indicating a high-energy wind environment. The most erosive winds (DP > 60 VU) occurred from February to June. Controlled by the wind field, dune morphology remained longitudinal from September to May. However, small longitudinal dunes (height below 5 m) transformed into transverse dunes from June to August, and formed a dune network with the large longitudinal dunes. On flat land, a series of active longitudinal dunes migrated at 7.8 to 15.1 m yr−1, with a mean of 11.9 m yr−1. Their dominant migration mode was parallel to the resultant drift direction (RDD), with the dunes extending downwind via accretion at the downwind ends. These dunes also migrate laterally by 0.4 to 0.8 m yr−1 while maintaining a symmetrical longitudinal dune morphology. These results expand our knowledge of dune migration and evolution, and provide guidance for protecting areas such as oases threatened by migrating dunes.

Characterization of Genetic Diversity in Dhofari Wild Gazelles

Wild gazelles are scattered in most of the arid and semi-arid areas of the Sultanate of Oman particularly in valleys, mountains and sandy zones of Rub' al Khali desert. Recently, gazelles’ populations have been facing reduction in the numbers. Consequently, gradual loss of genetic diversity is inevitable. This loss is considered one of the main threats that attribute to a loss of habitat and may lead to gazelle extinction. Till now, little is known about the status of the genetic diversity of the wild Dhofari gazelle. This project aimed to determine the extent of inbreeding, population structure and genetic diversity in the Dhofari gazelles’ populations. DNA was extracted from gazelles’ fecal samples using the human stool DNA extraction protocol. Following extraction, four microsatellite nuclear markers were used to calculate the level of inbreeding, population differentiation and genetic diversity. PCR inhibitors were significantly removed by the addition of Bovine Serum Albumin (BSA) and dimethyl sulfoxide (DMSO). The mean inbreeding for the population was 0.228 for all loci with a standard error of 0.09. It is therefore postulated that Dhofari gazelles are generally undergoing gradual inbreeding which could lead to lack of fitness in future generations. The genetic differentiation (Fst) ranged between 0.071 (between Gara and Stom) and 0.231 (between Gara and Ayon). On the other hand, the Fst estimate between Solot (most distant) versus other Dhofari gazelles populations (pooled together) was 3.7%. Principle Components Analysis clustered Ayon and Gara populations apart from one another and closer to Stom while placing Solot further than all other populations which is in agreement with the Fst results and the geographical distribution. In conclusion, the results of this preliminary study will provide insight towards the conservation of wild gazelles in Dhofar. This is the first study to report the genetic diversity and status of wild Gazelles and provides a reference point for future studies assessing their genetic diversity and variability.

Viscoelastic Model and Synthetic Seismic Data of Eastern Rub’Al-Khali

The Rub’ Al-Khali basin in Saudi Arabia remains unexplored and lacks data availability due to its remoteness and the challenging nature of its terrain. Thus far, there are neither digital geologic models nor synthetic seismic data from this specific area accessible for testing research techniques and analysis. In this study, we build a 2D viscoelastic model of the eastern part of the Rub’ Al-Khali basin and generate a corresponding dual-component seismic data set. We compile high-resolution depth models of compressional- and shear-wave velocities, density, as well as compressional- and shear-wave quality factors from published data. The compiled models span Neoproterozoic basement up to Quaternary sand dunes. We then use the finite-difference technique to model the propagation of seismic waves in the compiled viscoelastic medium of eastern Rub’ Al-Khali desert. In particular, we generate vertical and horizontal components of the shot gathers with accuracy to the fourth and second orders in space and time, respectively. The viscoelastic models and synthetic seismic datasets are made available in an open-source site for prospective re-searchers who desire to use them for their research. Users of these datasets are urged to make their findings also accessible to the geoscience community as a way of keeping track of developments related to the Rub’ Al-Khali desert.

A global analysis of diurnal variability in dust and dust mixture using CATS observations

Abstract. The current study investigates the diurnal cycle of dust and dust mixture loading across the global tropics, subtropics, and mid-latitudes by analyzing aerosol extinction and typing profiles observed by the Cloud-Aerosol Transport System (CATS) lidar aboard the International Space Station. According to the comparison with ground-based and other satellite observations, CATS aerosol and dust and dust mixture loading observations exhibit reasonable quality but significant day–night inconsistency. To account for this day–night inconsistency in CATS data quality, the diurnal variability in dust and dust mixture characteristics is currently examined separately for daytime and nighttime periods. Based on an analysis of variance (ANOVA) analytical framework, pronounced diurnal variations in dust and dust mixture loading are generally uncovered during daytime periods and over terrestrial areas. The current study identifies statistically significant diurnal variability in dust and dust mixture loading over key dust sources, including the Bodélé Depression, the West African El Djouf, Rub' al-Khali desert, and western and southern North America, confirming the previous observation-based findings regarding the diurnal cycle of dust emission and underlying meteorological processes in these regions. Significant seasonal and diurnal variability in dust and dust mixture is identified over the Iraqi and Thar deserts. The identified significant diurnal cycles in dust mixture loading over the vegetated regions in the Amazon and tropical southern Africa are hypothesized to be driven by enhanced dust emission due to wildfires.

Stratigraphy, palaeoclimatic context and fossils of the Southern Rub Al Khali (the Empty Quarter): results of a geo-archaeological survey around the area of Maitan in the Sultanate of Oman

ABSTRACT Here we summarise the geological work conducted in the desert village of Maitan, in South of Oman, during a geological and archaeological survey. The region is dominated by extensive, tall linear dunes overlying an incised Eocene marine limestone plateau. Above the limestone plateau, the interdunal areas expose various recent deposits including palaeo-regolith and epikarst deposits, fluvial conglomerates, gypsum «playa-like» deposits, aeolianites, semi-consolidated dunes, sand and silt with gypsum-roses, calcareous tufa and loose sand. The sediments indicate the prevalence of largely arid and hyper-arid conditions, with brief intervals of relatively humid conditions, during which humans and their livestock probably inhabited the region. The presence of abundant millstones, grindstones and pestles and mortars, along with fossilised animal bones, beads and other ornaments, scrapers, blades and other instruments, speaks for prolonged occupation of the area. The survey revealed the presence of Late Palaeolithic, Middle and Late Neolithic sites. The discovery of this new archaeological area provides extraordinary information about the middle Holocene peopling of this region, about which little was previously known. Comparisons with known sites in the Rub Al Khali desert show an incredibly high presence of living and moving human populations in an area which now seems so inhospitable.

Wilfred Thesiger and the Umm as Samim, Oman

Often our knowledge and understanding of the geology and geomorphology of some of the remotest areas of the world has had its roots in the observations of pioneering European explorers. This is particularly so in the Arabian Peninsula, where the Ar Rub' al Khali (‘the Empty Quarter’) desert is the largest contiguous sand desert in the world, 1200 km long and 650 km wide, covering some 650 000 km2. Extremely dry (hyper‐arid) and almost completely barren, it presented a formidable obstacle to explorers. Indeed, one of the earliest travellers across western Arabia, Charles Doughty, wrote in 1888 ‘I passed one good day in Arabia, and all the rest were evil’.

Dating Persistent Short-Term Human Activity in a Complex Depositional Environment: Late Prehistoric Occupation at Saruq al-Hadid, Dubai

ABSTRACTThe archaeological site of Saruq al-Hadid, Dubai, United Arab Emirates, presents a long sequence of persistent temporary human occupation on the northern edge of the Rub’ al-Khali desert. The site is located in active dune fields, and evidence for human activity is stratified within a deep sequence of natural dune deposits that reflect complex taphonomic processes of deposition, erosion and reworking. This study presents the results of a program of radiocarbon (14C) and thermoluminescence dating on deposits from Saruq al-Hadid, allied with studies of material remains, which are amalgamated with the results of earlier absolute dating studies provide a robust chronology for the use of the site from the Bronze Age to the Islamic period. The results of the dating program allow the various expressions of human activity at the site—ranging from subsistence activities such as hunting and herding, to multi-community ritual activities and large scale metallurgical extraction—to be better situated chronologically, and thus in relation to current debates regarding the development of late prehistoric and early historic societies in southeastern Arabia.

Saruq al-Hadid: a persistent temporary place in late prehistoric Arabia

ABSTRACTIn this paper, the authors use the site of Saruq al-Hadid – a ‘persistent temporary place’ located in the mobile dune fields of the north eastern edge of the Rub’ al-Khali desert – as a lens to focus discussion on the variable nature of temporary sites and mobile adaptations within the archaeology of southeastern Arabia, the relationships between temporary sites and permanent settlements, and the evidence for collective events and gatherings from later prehistory into the Islamic period. They discuss evolving arguments regarding sedentary and mobile sites and groups in Arabia from the Neolithic period to the Iron Age, and summarize the material record of human activity at Saruq al-Hadid. This research emphasizes the site’s changing significance as a temporary place and its emergence, in the early Iron Age, as a locus for periodic interaction between multiple community groups.

Synoptic analysis of dust storm over Arabian Peninsula: a case study on February 28, 2009

Sand and dust storms are causing hazards and problems in aviation as well as the dangers and distresses they cause on living things. The low meteorological visibility, the presence of strong winds with gust, and the transport of dust and sand particles by the wind are dangerous on landing and departure of aircrafts, and even on planes that are parked. The main aim of the study is to examine the meteorological conditions causing the dust storm that took place in the Arabian Peninsula on February 28, 2009, and to determine the source of dust caused dust storm, sand storm, blown sand, and blown dust at the airports. Within the scope of the study, aviation routine weather report (METAR) and aviation selected special weather report (SPECI) reports have been assessed at many airports over Arabian Peninsula (AP), the northern part of the AP and North Africa. As model outputs; NCEP–DOE Reanalysis 2 data, BSC–DREAM8B, and HYSPLIT model were used. In the satellite images; METEOSAT MSG dust RGB images, MODIS, and Kalpana-1 data were used. According to obtained results, dust storms were detected in Bahrain, Kuwait, Saudi Arabia, and United Arab Emirates (UAE). At Al-Ahsa Airport in Saudi Arabia, the lowest visibility measured on February 28, 2009, dropping to 200 m, which was dominated by blowing sand. The source region of the dust observed at Dubai Airport in UAE is the eastern regions of the Rub’al Khali Desert located between Saudi Arabia, Oman, and UAE.

Sand curve facelift: Empirical to polynomial model and the effect on the tomogram

An empirical thickness versus time relationship sand curve has been established in the Rub’ al-Khali desert and verified by a theoretical curve from the direct measurements of sand. The empirical sand curve has variable success in other areas of Saudi Arabia. We established a theoretical sand curve model to determine the single-way time in dry sand. Tomographic modeling of a higher resolution 3D seismic survey contributes more data to refine the relationship. Polynomial curves were used in the calculation of near-surface static corrections to improve the solution for low-relief structures.

Seasonal Aerosol Optical Depth (AOD) Variability Using Satellite Data and its Comparison over Saudi Arabia for the Period 2002?2013

ABSTRACTThis study analyzes the spatiotemporal variations of seasonal Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue (DB) AOD at 550 nm from the Aqua satellite over Saudi Arabia for the period 2002‒2013. Satellite retrieved AOD is also compared with AERONET AOD over the Solar Village and KAUST station. The result of the seasonal AOD spatial distribution shows that the peak AOD value of 0.6 is observed over Hafr Al Batin, Riyadh, and the Rub Al Khali desert during spring, whereas the Gizan area shows the peak AOD during summer. In contrast, the autumn shows the peak AOD value of 0.5 over Dhahran and in the proximity of Jeddah, whereas Hafr Al Batin, Al Khafji, Al Jubail, and the Rub Al Khali desert show the peak AOD value of 0.4 in winter. Regression analysis shows the AOD increasing trends during spring, summer, and autumn (except for winter) over the entire Saudi Arabia. Over the Solar Village, the AOD increasing trends are also noted during spring and summer, whereas autumn and winter display the AOD decreasing trends. The AOD increasing trends are displayed in all seasons over KAUST. Hence, the AOD increasing/decreasing trends indicate that the number of dust storms either increases or decreases over these regions. Over the Solar Village, the correlation values for MODIS DB AOD versus AERONET AOD are 0.77 (spring), 0.62 (summer), 0.65 (autumn), and 0.75 (winter). Likewise, over KAUST, the correlation values for the same pairing are 0.85 (spring), 0.71 (summer), 0.81 (autumn), and 0.89 (winter). The incorrect aerosol model selection and imperfect surface reflectance calculation are responsible for reducing the correlation. Therefore, this study recommends that the DB algorithm can be used effectively to detect AOD over Saudi Arabia, which will further help to improve the MODIS DB AOD product utilizing the next version of the algorithm.

Al-Ashoosh: a third-millennium BC desert settlement in the United Arab Emirates

The archaeological site of Al-Ashoosh is a third-millennium BC settlement located in the Rub al-Khali Desert (or Empty Quarter), 70km south of Dubai in the United Arab Emirates (UAE) (Figure 1). This site provides an excellent example of the type of occupation of the inland deserts of the Oman peninsula during the period following the Holocene Climatic Optimum. Between November 2015 and May 2016, the Dubai Municipality and the Sanisera Archaeology Institute conducted excavations at the site of Al-Ashoosh. This site was discovered during two seasons of survey in 2002–2003. This survey work, undertaken by the Dubai Municipality and the Department of Antiquities of Jordan, identified 33 archaeological sites ranging in date from prehistory to the late Islamic period. In 2006–2007, more-detailed archaeological investigations of the area of Al-Ashoosh were conducted, including survey, excavation and geological sampling (Casana et al.2009; Herrmann 2012; Contreras & Carcacer 2016).

Use of Spatial Technologies to Study the Winds’ Directions in Rub’ Al-Khali Desert, Saudi Arabia

Use of Spatial Technologies to Study the Winds’ Directions in Rub’ Al-Khali Desert, Saudi Arabia

Developing a framework of Quaternary dune accumulation in the northern Rub' al-Khali, Arabia

Located at the crossroads between Africa and Eurasia, Arabia occupies a pivotal position for human migration and dispersal during the Late Pleistocene. Deducing the timing of humid and arid phases is critical to understanding when the Rub' al-Khali desert acted as a barrier to human movement and settlement. Recent geological mapping in the northern part of the Rub' al-Khali has enabled the Quaternary history of the region to be put into a regional stratigraphical framework. In addition to the active dunes, two significant palaeodune sequences have been identified. Dating of key sections has enabled a chronology of dune accretion and stabilisation to be determined. In addition, previously published optically stimulated luminescence (OSL) dates have been put in their proper stratigraphical context, from which a record of Late Pleistocene dune activity can be constructed. The results indicate the record of dune activity in the northern Rub' al-Khali is preservation limited and is synchronous with humid events driven by the incursion of the Indian Ocean monsoon.

Climatic controls on the interannual to decadal variability in Saudi Arabian dust activity: Toward the development of a seasonal dust prediction model

AbstractThe observed climatic controls on springtime and summertime Saudi Arabian dust activities during 1975–2012 are analyzed, leading to development of a seasonal dust prediction model. According to empirical orthogonal function analysis, dust storm frequency exhibits a dominantly homogeneous pattern across Saudi Arabia, with distinct interannual and decadal variability. The previously identified positive trend in remotely sensed aerosol optical depth since 2000 is shown to be a segment of the decadal oscillation in dust activity, according to long‐duration station record. Regression and correlation analyses reveal that the interannual variability in Saudi Arabian dust storm frequency is regulated by springtime rainfall across the Arabian Peninsula and summertime Shamal wind intensity. The key drivers of Saudi Arabian dust storm variability are identified. Winter‐to‐spring La Niña enhances subsequent spring dust activity by decreasing rainfall across the country's primary dust source region, the Rub' al Khali Desert. A relatively cool tropical Indian Ocean favors frequent summer dust storms by producing an anomalously anticyclonic circulation over the central Arabian Peninsula, which enhances the Shamal wind. Decadal variability in Saudi Arabian dust storm frequency is associated with North African rainfall and Sahel vegetation, which regulate African dust emissions and transport to Saudi Arabia. Mediterranean sea surface temperatures (SSTs) also regulate decadal dust variability, likely through their influence on Sahel rainfall and Shamal intensity. Using antecedent‐accumulated rainfall over the Arabian Peninsula and North Africa, and Mediterranean SSTs, as low‐frequency predictors, and tropical eastern Pacific and tropical Indian Ocean SSTs as high‐frequency predictors, Saudi Arabia's seasonal dust activity is well predicted.