In this study, the geohydraulic parameters of aquifers in the Sahel Doukkala region, western Morocco were estimated using a geostatistical method to transform vertical electrical soundings (VES) data ...into electrical resistivity tomography (ERT) profiles. The resulting ERT profiles covered a larger area than the original VES data, allowing for a more comprehensive analysis. The obtained results indicated that the apparent and inverted resistivities range from 16 to 1558 Ohm.m and from 4 to 6980 Ohm.m, respectively, with a low inversion error (RMS) of 6.1–13.1%, demonstrating the reliability of the proposed approach. Using the inverted resistivities, the estimated hydraulic conductivity, effective porosity, and transmissivity ranged from 0.2 to > 103.7 m/day, 11.6% to > 45.8%, and 1.7 to > 2028.6 m
2
/day, respectively. These values reflect the sand, clayey sand, and limestone lithology prevalent in the study area, with medium to high aquifer potential. The validation of our results with pumping test data showed that the estimated geohydraulic parameters are representative of the geological formations in the study area. In addition to providing a rapid interpretation of the data, the present study offers fundamental insights for future research, contributing to better planning and management of groundwater resources.
The primary goals of this research are to detect the spatial variation of the hydrogeological characteristics and evaluate the groundwater quality in the eastern Nile River, Khartoum state, Sudan, ...using geophysical and hydrochemical methods. Thirteen Vertical electrical soundings (VES), using Schlumberger configuration, were measured along three profiles to characterize the groundwater aquifer. VES findings denoted that the study area comprises two hydraulically connected aquifers. The upper aquifer of sand has an average thickness of 50 m, and the lower aquifer is composed of sandstone of a thickness of up to 300 m. The results of VES inversion were further used to measure aquifer characteristics, including transverse resistance, longitudinal conductance, hydraulic conductivity, and transmissivity. The detected average values of these parameters were 6690 Ωm
2
, 1.4 Ω
−1
, 264 m
2
/d and 4 m/day, respectively. In addition, regression analysis was performed to suggest local relationships for estimating aquifer characteristics within the study area. On the other hand, total longitudinal conductance was used to predict the protective strength of the hydrogeological columns, ranging from 1.7 to 5.8 Ω
−1
; as a result, the protective capacity of the aquifer ranged from good to very good, suggesting potable water quality. This result was subsequently confirmed by the groundwater quality index (GWQI) model. Eleven physiochemical parameters analyzed for nine boreholes were used in GWQI estimation to assess groundwater quality in the study area. The primary analysis of the hydrochemical parameters indicated that almost all parameters are below permissible limits prescribed by the World Health Organization (WHO). The computed GWQI varies between 34.8 and 148, and the majority of groundwater samples, precisely 55.5%, are good water types, while 22.2% of the samples are in an excellent quality state. This research concluded that the groundwater aquifer in the study area is ideal for groundwater exploitation. However, applying a detailed geophysical and hydrochemical survey is recommended to reduce the uncertainty of the resulting models.
Three-dimensional radar reflectivity fields from a dual-wavelength Doppler polarimetric radar (S-PolKa) deployed in the equatorial Indian Ocean are used to evaluate the composition of the population ...of convective cloud elements during active phases of the MJO. Rainfall in active periods was intermittent, occurring in 11 episodes of about 2-4 days, separated by several nonrainy days. Data for these 2-day periods were composited relative to the time of maximum rainfall. Analysis of the S-PolKa data shows the makeup of the convective population during the rainfall episodes. Four types of echo structures were analyzed statistically for the 11 rainfall episodes: shallow convective echoes (SCE), deep convective cores (DCC), wide convective echo cores (WCC), and broad stratiform (BSR) echo regions. SCE and DCC events were most frequent before the maximum rainfall, with the peak frequency of SCE leading that of DCCs. WCCs were most frequent during the rainfall maximum, and BSR regions were most frequent in the later part of the rainfall episode. Composited ECMWF Interim Re-Analysis (ERA-Interim) data and 3-hourly atmospheric soundings indicate that the 2-4-day episodes were related to the passage of equatorial waves. In the early part of a rainfall episode, the wave-passage conditions were unstable, favoring deep penetrating convective elements, while in the later period the wave divergence profile was commensurate with convective systems in late anvil-producing stages. These results support the stretched building-block notion of the life cycle of tropical convection and confirm satellite-based interpretations of SCE, DCC, WCC, and BSR statistics in the composition of the convective population.
The investigated region is located in the western desert fringes of the Nile Valley which requires studies of groundwater related to the many projects of land reclamation. The key objective of this ...paper is to estimate the qualitative and geometrical features of the investigated aquifer. Using 60 vertical electrical sounding and time-domain electromagnetic soundings allows us to suggest one possible model of the geometrical features of the local aquifer. A hydrogeological monitoring has been undertaken to investigate the current groundwater situation at the Gallaba plain. Such hydrological monitoring has not been undertaken before in detail. The results show that the investigated region has high groundwater potentialities in two main aquifers which belong to Pleistocene: shallow fresh water and deep brackish water. The lithological and structural elements contribute mainly to recharge and store the groundwater in the western part of the River Nile in Kom Ombo graben. The geochemical properties of the groundwater of the studied aquifers reflect meteoric water, which is a fresh to slightly brackish water. The small amount of groundwater salinity arises from silicate weathering and evaporation processes occurring in the aquifer matrix. Moreover, most of the studied groundwater samples are unfit for human consumption. Such samples are very satisfactory for livestock and poultry purposes and they can be used for irrigation using modern and improved irrigation methods e.g. sprinkler and drip methods. Furthermore, the hydrogeological monitoring of the concerned area indicates that it has high groundwater potentialities which will support its sustainable development.
The Orbiting Carbon Observatory-2 (OCO-2) carries and points a three-channel imaging grating spectrometer designed to collect high-resolution, co-boresighted spectra of reflected sunlight within the ...molecular oxygen (O2) A-band at 0.765 microns and the carbon dioxide (CO2) bands at 1.61 and 2.06 microns. These measurements are calibrated and then combined into soundings that are analyzed to retrieve spatially resolved estimates of the column-averaged CO2 dry-air mole fraction, XCO2. Variations of XCO2 in space and time are then analyzed in the context of the atmospheric transport to quantify surface sources and sinks of CO2. This is a particularly challenging remote-sensing observation because all but the largest emission sources and natural absorbers produce only small (< 0.25 %) changes in the background XCO2 field. High measurement precision is therefore essential to resolve these small variations, and high accuracy is needed because small biases in the retrieved XCO2 distribution could be misinterpreted as evidence for CO2 fluxes. To meet its demanding measurement requirements, each OCO-2 spectrometer channel collects 24 spectra s−1 across a narrow (< 10 km) swath as the observatory flies over the sunlit hemisphere, yielding almost 1 million soundings each day. On monthly timescales, between 7 and 12 % of these soundings pass the cloud screens and other data quality filters to yield full-column estimates of XCO2. Each of these soundings has an unprecedented combination of spatial resolution (< 3 km2/sounding), spectral resolving power (λ∕Δλ > 17 000), dynamic range (∼ 104), and sensitivity (continuum signal-to-noise ratio > 400). The OCO-2 instrument performance was extensively characterized and calibrated prior to launch. In general, the instrument has performed as expected during its first 18 months in orbit. However, ongoing calibration and science analysis activities have revealed a number of subtle radiometric and spectroscopic challenges that affect the yield and quality of the OCO-2 data products. These issues include increased numbers of bad pixels, transient artifacts introduced by cosmic rays, radiance discontinuities for spatially non-uniform scenes, a misunderstanding of the instrument polarization orientation, and time-dependent changes in the throughput of the oxygen A-band channel. Here, we describe the OCO-2 instrument, its data products, and its on-orbit performance. We then summarize calibration challenges encountered during its first 18 months in orbit and the methods used to mitigate their impact on the calibrated radiance spectra distributed to the science community.
This paper presents an integrated digital methodology for the generalization of soundings. The input for the sounding generalization procedure is a high resolution Digital Terrain Model (DTM) and the ...output is a sounding data set appropriate for portrayal on harbour and approach Electronic Navigational Charts (ENCs). The sounding generalization procedure follows the “ladder approach” that is a requisite for the portrayal of soundings on nautical charts, i.e., any sounding portrayed on a smaller scale chart should also be depicted on larger scale charts. A rhomboidal fishnet is used as a supportive reference structure based on the cartographic guidance for soundings to display a rhombus pattern on nautical charts. The rhomboidal fishnet cell size is defined by the depth range and the compilation scale of the charted area. Generalization is based on a number of rules and constraints extracted from International Hydrographic Organization (IHO) standards, hydrographic offices’ best practices and the cartographic literature. The sounding generalization procedure can be implemented using basic geoprocessing functions available in the most commonly used Geographic Information System (GIS) environments. A case study was performed in the New York Lower Bay area based on a high resolution National Oceanic and Atmospheric Administration (NOAA) DTM. The method successfully produced generalized soundings for a number of Harbour and Approach nautical charts at 10 K, 20 K, 40 K and 80 K scales.
Abstract
Satellite images frequently show mesoscale arc-shaped cloud lines with a spacing of several tens of kilometers. These clouds form in a shallow mixed boundary layer in locations where the ...near-surface horizontal wind speed exceeds ~7 m s
−1
. Unlike other mesoscale cloud line phenomena, such as horizontal convective rolls, these cloud lines do not align with the wind direction but form at large oblique angles to the near-surface wind. A particularly distinct event of this pattern developed on 31 January 2020 over the western tropical Atlantic Ocean. Radiosonde soundings are available for this time and location, allowing a detailed analysis. By comparing observations with theoretical predictions that are based on Jeffreys’s drag-instability mechanism, it is shown that drag-instability waves may contribute to the formation of this cloud pattern. The theory is formulated in only two dimensions and predicts that wavelike horizontal wind perturbations of this wavelength can grow, because they modulate the surface friction in a way that reinforces the perturbations. The theoretical horizontal wavelengths of 40–80 km agree with the observations. Streamlines from the ERA5 reanalysis show that the directional change of the near-surface wind is likely to contribute to the arc shape but that a radial propagation of an initial instability is also required to explain the strong curvature. Moreover, ERA5 winds suggest that other known explanations for the formation of cloud lines are unlikely to apply in the case studied here.
At the end of summer, the episode of atmospheric instability in the Moldavia region, is attributed to the predominantly eastern circulation, which directed air masses from the Asian continent to ...Romania. This context is the result of the presence of a high-pressure area, located in northern Siberia and extended to north-eastern Europe. Romania was located in the flow of the eastern circulation, behind the warm front.
The emersion of unforeseen factors, as was the case with the transport of dust from the dry regions of Asia, due to background of a circulation from the east, or the specificities of the relief, make it difficult to forecast the phenomena associated with instability. In this sense, atmospheric soundings are among the most used tools in forecasting atmospheric instability. In this sense, we used atmospheric soundings estimated by the GFS and ECMWF numerical forecast models to analyze the atmosphere vertically. Also, the cross-section profiles drawn in the EUMeTrain application showed the differences between the west and the east of Moldavia and described the vertical atmosphere in the analysed interval.
The evolution of the convective episode was described through satellite images. The forecast models anticipated the instability but did not estimate the amounts of cumulative precipitation. The increase in the amount of precipitation was, among other things, attributed to the existence in the atmosphere of Moldavia of dust particles that acted as condensation nuclei that increased the amount of precipitation. High concentrations of dust were also noticed after consistent rain showers, as explained by Cloudnet data processed.
The analysed case was one of the most representative instability episodes for summer of 2022 in Moldavia and played a decisive role in the soil water reserve.
Here’s how air quality and changes in the atmosphere have a major impact on the environment. The notable frequency of detected electrical discharges, was probably also the result of the presence in the atmosphere of suspended dust particles (due to a natural air pollution process), driven towards the Moldavia region.
Characteristics of tropospheric low‐frequency gravity waves are diagnosed in radiosonde soundings from the Tropical Warm Pool‐International Cloud Experiment near Darwin, Australia. The waves have ...typical vertical wavelengths of about 4 km, horizontal wavelengths of about 600 km, and intrinsic periods of about 12 hr. These scales match those of the vertical, horizontal, and temporal variability found in area‐averaged horizontal wind divergence over the same domain. Vertical profiles of divergence show wave‐like structures with variability of the order of 2
× 10
−5 s
−1 in the free troposphere. The results for Darwin are similar to previously reported observed mesoscale patterns of divergence/convergence over the tropical Atlantic. The findings imply that tropical divergence on spatial scales of a few hundred kilometers, which is known to influence the organization of convection, may be forced by gravity waves.
Plain Language Summary
On horizontal scales of several tens to hundreds of kilometers, which we call “mesoscale,” mean vertical motion is very small compared to mean horizontal motion. Yet the vertical motion exerts a critical influence on the formation of clouds: Large‐scale descent is associated with fair weather, and ascent is associated with cloudiness. Weather and climate modeling often assumes that mesoscale vertical motion varies slowly in the three spatial dimensions and with time. Recent observations over the tropical Atlantic, however, showed strong variability in mesoscale vertical motion, implying that clouds do not only respond to vertical motion but may themselves trigger vertical motion in their vicinity. This study reports similar variability also near Darwin, Australia. One way in which clouds can trigger remote vertical motion is by emitting waves, similar to stones that are thrown into a pond. This study examines vertical profiles of horizontal wind speed that were measured by instruments on ascending balloons near Darwin, Australia. These observations do indeed show waves that can provide a plausible explanation for the patterns of noteworthy variability in mesoscale motions. These findings suggest a two‐way coupling of clouds to their environment with potentially important consequences for our understanding of weather and climate phenomena.
Key Points
Mesoscale divergence profiles near Darwin show similar long‐lived fine‐scale vertical structure to that reported over the tropical Atlantic
High‐resolution soundings are used to test if gravity waves can serve as a plausible explanation for the observed divergence variability
Results imply that spatial and temporal variability of mesoscale horizontal divergence are consistent with a forcing by gravity waves
Issue
Geodiversity (i.e., the variation in Earth's abiotic processes and features) has strong effects on biodiversity patterns. However, major gaps remain in our understanding of how relationships ...between biodiversity and geodiversity vary over space and time. Biodiversity data are globally sparse and concentrated in particular regions. In contrast, many forms of geodiversity can be measured continuously across the globe with satellite remote sensing. Satellite remote sensing directly measures environmental variables with grain sizes as small as tens of metres and can therefore elucidate biodiversity–geodiversity relationships across scales.
Evidence
We show how one important geodiversity variable, elevation, relates to alpha, beta and gamma taxonomic diversity of trees across spatial scales. We use elevation from NASA's Shuttle Radar Topography Mission (SRTM) and c. 16,000 Forest Inventory and Analysis plots to quantify spatial scaling relationships between biodiversity and geodiversity with generalized linear models (for alpha and gamma diversity) and beta regression (for beta diversity) across five spatial grains ranging from 5 to 100 km. We illustrate different relationships depending on the form of diversity; beta and gamma diversity show the strongest relationship with variation in elevation.
Conclusion
With the onset of climate change, it is more important than ever to examine geodiversity for its potential to foster biodiversity. Widely available satellite remotely sensed geodiversity data offer an important and expanding suite of measurements for understanding and predicting changes in different forms of biodiversity across scales. Interdisciplinary research teams spanning biodiversity, geoscience and remote sensing are well poised to advance understanding of biodiversity–geodiversity relationships across scales and guide the conservation of nature.
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