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Along the western coastal plain of the Red Sea, the discovery of lithic tools proved that the occurrence of archaeological remains belonged to the Stone Age era. Unfortunately, until recently, most of the Stone Age site plans in the western Red Sea periphery have been unknown because of change in climate in addition to covering these sites with a large layer of sand. Recently, remote sensing (RS) data have proven to be effective at identifying buried archaeological sites using radar satellite imagery due to their ability to penetrate the land surface. This paper aims to identify and reconstruct several potential Stone Age sites using radar satellite images in the Tokar region, North-Eastern Sudan, on the western plain of the Red Sea. Radar (Sentinel-1 SAR GRD: C-band) data were processed utilizing the advantages of the Google Earth Engine platform and Snap software. The results of this research showed that some potential settlements belonging to the Stone Age era (expectedly dating back to the end of the Pleistocene and/or the initial phase of the Holocene) have subcircular shapes with some interior subcircles. These results shed new light on the potential construction technique, size, and function of the settlement in the Stone Age era and can provide some initial insights into the ancient lifestyle in this region. Additionally, this study can aid in future archaeological surveys and excavation missions in this region. [ABSTRACT FROM AUTHOR]

Extensive studies have been carried out on the characteristics of quantum radar cross section (QRCS) of targets. However, one crucial question related to multi-photon quantum radar cross section (M-QRCS) for targets in the atmospheric medium has not been explored yet. Understanding this question is vital for target detection and identification of quantum radar. This paper presents a universal method to solve M-QRCS in a homogeneous atmospheric medium (HAM-QRCS). The process is based on the photon wave function in a homogeneous atmospheric medium and the interaction mechanism of multi-photon and multiple atoms. It is suitable for analyzing the HAM-QRCS characteristics of targets of arbitrary shapes. The simulation results show that the molecules, particles, and other factors in the atmospheric medium cause the signal photons' energy to decrease and the propagation direction to change, leading to a decrease in the target return responses. However, in a specific angle range, as the photon number increases, the main lobe and first side lobe structures of the bistatic HAM-QRCS response are enhanced. These findings can be utilized to design target detection strategies and optimize stealth target structures of the quantum radar in the atmospheric medium. [ABSTRACT FROM AUTHOR]

This paper presents studies on using Sentinel-1 imagery data to determine the attributes of mixed forest stands. The fieldwork is carried out in Kostroma, Vologda, and Arkhangelsk oblasts and the Udmurt Republic. The study reveals that quantitative and qualitative forest characteristics correlate with radar survey parameters; the value of this correlation is identified. The results make it possible to zone a study area according to the standing volume and forest density. [ABSTRACT FROM AUTHOR]

Mangroves offer many socioeconomic and ecological benefits which can be lost due to damage caused by tropical cyclones. Thus, it is important to monitor the damage and recovery more accurately after these events to protect their benefits. In this study, mapping of mangrove damage and recovery was done using Sentinel-1 radar data after Tropical Cyclone Yasa in Suva-Navua, Fiji. Mature mangroves first needed to be discriminated from herbaceous, sapling and damaged mangroves, and then the distribution of mangroves corresponding to phenology seasons was calculated over three years. The ability to discriminate mature mangroves was found to vary with phenological season and before/after the cyclone event. Before the cyclone, poor classification of mature mangroves was observed in the Start of Season and the Peak Growth seasons due to full canopy cover causing radar signal attenuation. After the cyclone event, when there was damage to the mature mangroves, the reduced canopy cover improved the ability to discriminate the mature mangroves as the radar attenuation was reduced. A 7% loss of mature mangroves was observed from the End of Season to Start of Season in the post-cyclone period and a subsequent 6% gain was then observed from Start of Season to Peak Growth season in Suva-Navua. Time series Sentinel-1 data can be used to discriminate mature mangroves from other vegetation types in tropical regions where optical data acquisition is significantly impacted by cloud cover; however, it is important to account for phenological seasons to improve estimates of mature mangrove damage and recovery due to canopy-signal attenuation relationship. The next step in this research is to explore if there is optimal time series of radar data for monitoring mature mangroves in a post-cyclone period. [ABSTRACT FROM AUTHOR]

The sea surface velocity measurements obtained during the period of 2014–2016 using two high-frequency radars (HFR), which were installed on the northern coast of Vietnam, were reprocessed by using a variational approach (EOF/2dVar) to provide an extended dataset. The high temporal resolution of measurements and large spatial coverage of the radar data enabled the assessment of the surface circulation in the data-poor region of the southern Gulf of Tonkin (GoT) and the characterization of its temporal variations in a wide range of scales: from tidal frequency to annual cycle. It was found that tidal motions account for a large percentage (approximately 60%) of surface current variability in the GoT. The temporal variability of the kinetic energy of the surface currents is tightly correlated with wind variations in the monsoon-dominated atmospheric circulation system. Stratification, induced by the discharge of the Red River, also affects the tidal currents within the coastal region (~ 40 km wide) by modifying the tidal ellipses polarizations. Close to the shore, the prominent coastal flow experiences large temporal variations in response to wind and buoyancy forcing. The seasonal variability of the zonal wind component was found to play a significant role in coastal flow speed variations through the cross-shore mass exchange. The Red River freshwater discharge controls the seaward extension of the coastal flow and causes asymmetry in the seasonal variability of flow velocity. The data obtained and analysis results could be useful for the improvement of the regional circulation models, for further studies of the physical and biological processes in the GoT, and for marine resource management. [ABSTRACT FROM AUTHOR]

Possibilities of using radar polarimetry methods for identifying landslide zones are analyzed. The transformation of the dominant mechanism of signal scattering by the reflecting surface was used as a key feature of landslide zones. The polarimetric data from the PALSAR-2 radar of the ALOS-2 satellite are processed using the Freeman–Durden and Cloude–Pottier decompositions at four test sites selected in the region of the landslide caused by the collapse of the bank of the Bureya River. It is found that the results of decompositions are consistent with each other; however, in some areas there are significant differences due to the specific features of the basic model assumptions. It is shown that, before the descent of the landslide masses, three main mechanisms of radar signal scattering existed in the analyzed region: single surface, volumetric, and double scattering. After the collapse, this area was dominated by single scattering characteristic of the reflective surface with large-scale irregularities free of vegetation, due to which the landslide descent zone can be confidently recognized. The significant potential of using radar polarimetry for remote diagnostics of the consequences of landslide phenomena has been demonstrated. [ABSTRACT FROM AUTHOR]

Criteria for the localization of gold deposits within the Ayan–Yuryakh anticlinorium in Magadan oblast have been developed using processed satellite imagery data and the analysis of geological and geophysical materials. The structural elements are linear, arc, ring, and concentric lineaments of the first (11–35 km), second (5–10 km), and third (less than 5 km) rank. The ring structures of the second and third rank form linear chains confined to the hidden linear structures of the northwest and north-northeast strike. Gold deposits occur in the central or peripheral parts of the ring structures of the second rank at the intersections of the latter with regional sublatitudinal faults. The area of ​​the Pavlik deposit has a block structure, due to the dominant faults of the northwestern strike, complicated by faults of the northeastern and meridional strike, as well as arc structural elements. When predicting prospective ore areas, the localization patterns of gold ore, determined by the results of gravimetric and gamma surveys, should be taken into account. [ABSTRACT FROM AUTHOR]

The article discusses the possibility of determining surface elevation using a conventional spaceborne synthetic aperture radar (SAR) survey by one satellite without interferometric phase measurements of the slant range. The capabilities of such determination are examined. A schematic diagram is given. Advantages and disadvantages are analyzed. [ABSTRACT FROM AUTHOR]

The use of remote sensing for monitoring of submerged aquatic vegetation (SAV) in fluvial environments has been limited by the spatial and spectral resolution of available image data. The absorption of light in water also complicates the use of common image analysis methods. This paper presents the results of a study that uses very high-resolution image data, collected with a Near Infrared sensitive DSLR camera, to map the distribution of SAV species for three sites along the Desselse Nete, a lowland river in Flanders, Belgium. Plant species, including Ranunculus peltatus, Callitriche obtusangula, Potamogeton natans L., Sparganium emersum R. and Potamogeton crispus L., were classified from the data using object-based image analysis and expert knowledge. A classification rule set based on a combination of both spectral and structural image variation (e.g. texture and shape) was developed for images from two sites. A comparison of the classifications with manually delineated ground truth maps resulted for both sites in 61% overall accuracy. Application of the rule set to a third validation image resulted in 53% overall accuracy. These consistent results not only show promise for species-level mapping in such biodiverse environments but also prompt a discussion on assessment of classification accuracy. [ABSTRACT FROM AUTHOR]

A deeper understanding of how clouds will respond to a warming climate is one of the outstanding challenges in climate science. Uncertainties in the response of clouds, and particularly shallow clouds, have been identified as the dominant source of the discrepancy in model estimates of equilibrium climate sensitivity. As the community gains a deeper understanding of the many processes involved, there is a growing appreciation of the critical role played by fluctuations in water vapor and the coupling of water vapor and atmospheric circulations. Reduction of uncertainties in cloud-climate feedbacks and convection initiation as well as improved understanding of processes governing these effects will result from profiling of water vapor in the lower troposphere with improved accuracy and vertical resolution compared to existing airborne and space-based measurements. This paper highlights new technologies and improved measurement approaches for measuring lower tropospheric water vapor and their expected added value to current observations. Those include differential absorption lidar and radar, microwave occultation between low-Earth orbiters, and hyperspectral microwave remote sensing. Each methodology is briefly explained, and measurement capabilities as well as the current technological readiness for aircraft and satellite implementation are specified. Potential synergies between the technologies are discussed, actual examples hereof are given, and future perspectives are explored. Based on technical maturity and the foreseen near-mid-term development path of the various discussed measurement approaches, we find that improved measurements of water vapor throughout the troposphere would greatly benefit from the combination of differential absorption lidar focusing on the lower troposphere with passive remote sensors constraining the upper-tropospheric humidity. [ABSTRACT FROM AUTHOR]

Satellite remote sensing technology has been widely used in environmental protection in China. Based on China's environmental protection characteristics, this paper reviews the application advancements of optical, infrared, microwave and hyperspectral satellite remote sensing techniques in atmospheric environment, water environment and ecological environment, respectively, including the atmospheric environment monitoring of aerosols, particulate matter, pollution gases, and greenhouse gases; the water environment monitoring of water blooms water quality, oil spills, water pollution and drinking water safety; the ecological environment monitor of national nature reserves, environmental damages from mines development, soil contamination, urban/rural ecological environment and biodiversity richness. Furthmore, it summarizes the limitations and future directions of satellite remote sensing studies in China environmental protection. The paper specifically notes that the development of high-resolution satellite remote sensing technology, as well as the launch and use of China series satellites could significantly improve the level of government's environmental management. [ABSTRACT FROM AUTHOR]

The signal measured by heave-pitch-roll directional wave buoys yields the first four coefficients of a Fourier series. Data adaptive methods must be employed to estimate a directional wave spectrum. Marine X-band radars (MRs) have the advantage over buoys that they can measure 'model-free' two-dimensional (2D) wave spectra. This study presents the first comprehensive validation of MR-derived multi-directional wave characteristics. It is based on wave data from the 2010 Impact of Typhoons on the Ocean in the Pacific (ITOP) experiment in the Philippine Sea, namely MR measurements from R/V Roger Revelle, Extreme Air-Sea Interaction (EASI) buoy measurements, as well as WAVEWATCH-III (WW3) modeling results. Buoy measurements of mean direction and spreading as function of frequency, which do not require data adaptive methods, are used to validate the WW3 wave spectra. An advanced MR wave retrieval technique is introduced that addresses various shortcomings of existing methods. Spectral partitioning techniques, applied to MR and WW3 results, reveal that multimodal seas are frequently present. Both data sets are in excellent agreement, tracking the evolution of up to 4 simultaneous wave systems over extended time periods. This study demonstrates MR's and WW3's strength at measuring and predicting 2D wave spectra in swell-dominated seas. [ABSTRACT FROM AUTHOR]

An integrated [very low frequency (VLF) electromagnetic, magnetic, remote sensing, field, and geographic information system (GIS)] study was conducted over the basement complex in southern Sinai (Feiran watershed) for a better understanding of the structural controls on the groundwater flow. The increase in satellite-based radar backscattering values following a large precipitation event (34 mm on 17-18 January 2010) was used to identify water-bearing features, here interpreted as preferred pathways for surface water infiltration. Findings include: (1) spatial analysis in a GIS environment revealed that the distribution of the water-bearing features (conductive features) corresponds to that of fractures, faults, shear zones, dike swarms, and wadi networks; (2) using VLF (43 profiles), magnetic (7 profiles) techniques, and field observations, the majority (85 %) of the investigated conductive features were determined to be preferred pathways for groundwater flow; (3) northwest-southeast- to north-south-trending conductive features that intersect the groundwater flow (southeast to northwest) at low angles capture groundwater flow, whereas northeast-southwest to east-west features that intersect the flow at high angles impound groundwater upstream and could provide potential productive well locations; and (4) similar findings are observed in central Sinai: east-west-trending dextral shear zones (Themed and Sinai Hinge Belt) impede south to north groundwater flow as evidenced by the significant drop in hydraulic head (from 467 to 248 m above mean sea level) across shear zones and by reorientation of regional flow (south-north to southwest-northeast). The adopted integrated methodologies could be readily applied to similar highly fractured basement arid terrains elsewhere. [ABSTRACT FROM AUTHOR]

The year-round continuous remote sounding of the atmospheric boundary layer (ABL) by means of the Doppler acoustic radar (sodar) LATAN-3 has been performed at the Zvenigorod Scientific Station of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, since 2008. A visual analysis of sodar echograms for four years revealed a large number of wavelike patterns in the intensity field of a scattered sound signal. Similar patterns were occasionally identified before in sodar, radar, and lidar sounding data. These patterns in the form of quasi-periodic inclined stripes, or cat's eyes, arise under stable stratification and significant vertical wind shears and result from the loss of the dynamic stability of the flow. In the foreign literature, these patterns, which we call internal gravity-shear waves, are often associated with Kelvin-Helmholtz waves. In the present paper, sodar echograms are classified according to the presence or absence of wavelike patterns, and a statistical analysis of the frequency of their occurrence by the year and season was performed. A relationship between the occurrence of the patterns and wind shear and between the wave length and amplitude was investigated. The criteria for the identification of gravity-shear waves, meteorological conditions of their excitation, and issues related to their observations were discussed. [ABSTRACT FROM AUTHOR]