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  • Articles  (160)
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  • 1
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    Unknown
    Wiley-Blackwell
    Publication Date: 2018-03-12
    Description: No abstract is available for this article.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2018-03-07
    Description: Landslides have been observed in different terrestrial environments and also on planets, satellites, and asteroids. Long runout landslides are strongly dependent on the initial mass position, material and slope path properties, topographic relief, and presence of volatiles. Therefore, landslides represent a means for the description of rock properties and environment of deposition prevailing at the time of occurrence, and may assist understanding the geological and climatological history of the planetary surfaces. Concerning Mars, previous studies have concentrated on Valles Marineris, where among the largest and longest landslides have been observed. Using different imagery, we present and analyse an original database of 3,118 Martian landslides of deposit area greater than 0.1 km 2 throughout the planet between 60°n and 60°S, resulting in a dataset far richer than previously done. After a distinction is made between different typologies of landslides, their position and the statistical distribution of their geometrical properties are examined. Large landslides cluster along the Noctis Labyrinthus – Valles Marineris – Margaritifer Terra system. Rock avalanches within craters are widespread, but no significant large landslides have been found at latitudes higher than 40°S and 46°N. The magnitude-frequency distribution follows a power-law with scaling exponent ranging between 1.02 and 1.57, for the entire dataset, and varies according to the geomorphological settings, the landslide typology, and mobility. A volume-area power law relationship (exponent: 1.12-1.24) is proposed, based on the reconstruction of 222 landslide geometries, and compared to those for similar terrestrial landslides (1.39). Similarities with respect to terrestrial landslide, distribution with respect to impact craters and impact energy, and cryosphere extent are also discussed.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 3
    Publication Date: 2018-03-07
    Description: The gravitational effects of the atmosphere and subsurface water are significant obstacles to observing gravity variations on the sub-μGal (1 μGal = 10 nm/s 2 ) scale. The goal of this study is to detect changes in gravity that are caused by mass redistributions deep underground related to seismological phenomena by reducing environmental gravity effects using multiple gravimeters below- and aboveground, which we term a “vertical gravimeter array”. Based on an evaluation of the responses to atmospheric effects and rainfall events identified in observations made with individual relative gravimeters, the vertical gravimeter array succeeds in stacking the target signals from deep underground and in reducing errors due to rainfall or free groundwater and atmospheric effects. To enable accurate interpretation, we introduce a physical approach that is based on attraction and loading deformation effects for atmospheric reduction using state-of-the-art gridded weather data products. Changes in the water levels of confined groundwater can be regarded as a signal from deep underground, and a response coefficient of approximately −15 μGal/m was obtained. In addition, the response coefficient of the free groundwater level was determined to be approximately 5 μGal/m. Such array observations are expected to contribute to monitoring crustal activity and hydrological studies.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 4
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    Unknown
    Wiley-Blackwell
    Publication Date: 2018-02-18
    Description: No abstract is available for this article.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 5
    Publication Date: 2018-01-27
    Description: The link between pollution and health is commonly explored by trying to identify the dominant cause of pollution and its most significant effect on health outcomes. The use of multivariate features to describe exposure is less explored because investigating a large domain of scenarios is theoretically (i.e. interpretation of results) and technically (i.e. computational effort) challenging. In this work we explore the use of Bayesian Networks with a multivariate approach to identify the probabilistic dependence structure of the environment-health nexus. This consists of environmental factors (topography, climate), exposure levels (concentration of outdoor air pollutants) and health outcomes (mortality rates). The information is collated with regard to a data-rich study area: the English regions (United Kingdom), which incorporate environmental types that are different in character from urban to rural. We implemented a reproducible workflow in the the R programming language to collate environment-health data and analyze almost 50 millions of observations making use of a graphical model (Bayesian Network) and Big Data technologies. Results show that for pollution and weather variables the model tests well in sample, but also has good predictive power when tested out of sample. This is facilitated by a training/testing split in the data along time and space dimension and suggests that the model generalises well to new regions and time periods.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 6
    Publication Date: 2018-01-18
    Description: We introduce a new method to determine the anisotropy of reflectance of sea ice and snow at spatial scales from 1 m 2 to 80 m 2 using a multispectral circular fish-eye radiance camera (CE600). The CE600 allows measuring radiance simultaneously in all directions of a hemisphere at a 1°angular resolution. The spectral characteristics of the reflectance and its dependency on illumination conditions obtained from the camera are compared to those obtained with a hyperspectral field spectroradiometer manufactured by Analytical Spectral Device, Inc. (ASD). Results confirm the potential of the CE600, with the suggested measurement set-up and data processing, to measure commensurable sea ice and snow Hemispherical Directional Reflectance Factor, HDRF, values. Compared to the ASD, the reflectance anisotropy measured with the CE600 provides much higher resolution in terms of directional reflectance (N=16020). The hyperangular resolution allows detecting features that were overlooked using the ASD due to its limited number of measurement angles (N = 25). This dataset of HDRF further documents variations in the anisotropy of the reflectance of snow and ice with the geometry of observation and illumination conditions and its spectral and spatial scale dependency. Finally, in order to re-produce the hyperangular CE600 reflectance measurements over the entire 400-900 nm spectral range, a regression based method is proposed to combine the ASD and CE600 measurements. Results confirm that both instruments may be used in synergy to construct a hyperangular and -spectral snow and ice reflectance anisotropy dataset.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 7
    Publication Date: 2018-01-12
    Description: Using six flights observations in September 2015 over Hebei, China, this study shows a robust negative aerosol-cloud droplet effective radius (r e ) relationship for liquid clouds, which is different from previous studies that found positive aerosol-cloud r e relationship over east China using satellite observations. Total of 27 cloud samples were analyzed with the classification of clean and polluted conditions using lower and upper 1/3 rd aerosol concentration at 200 m below the cloud bases. By normalizing the profiles of cloud droplet r e , we found significant smaller values under polluted than under clean condition at most heights. Moreover, the averaged profiles of cloud LWC show larger values under polluted than clean conditions, indicating even stronger negative aerosol-cloud r e relationship if LWC is kept constant. The droplet size distributions further demonstrate that more droplets concentrate within smaller size ranges under polluted conditions. Quantitatively, the aerosol-cloud interaction is found around 0.10-0.19 for the study region.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 8
    Publication Date: 2018-01-12
    Description: Most of the global climate models (GCMs) in the Coupled Model Intercomparison Project, phase 5 (CMIP5) do not include precipitating ice (a.k.a. falling snow) in their radiation calculations. We examine the importance of the radiative effects of precipitating ice on simulated surface wind stress and sea surface temperatures (SSTs) in terms of seasonal variation and in the evolution of Central Pacific El Nino (CP-El Nino) events. Using controlled simulations with the CESM1 model, we show that the exclusion of precipitating ice radiative effects generates a persistent excessive upper-level radiative cooling and an increasingly unstable atmosphere over convective regions such as the western Pacific and tropical convergence zones. The invigorated convection leads to persistent anomalous low-level outflows which weaken the easterly trade winds, reducing upper-ocean mixing and leading to a positive SST bias in the model mean state. In CP-El Nino events, this means that outflow from the modeled convection in the central Pacific reduces winds to the east, allowing unrealistic eastward propagation of warm SST anomalies following the peak in CP-El Nino activity. Including the radiative effects of precipitating ice reduces these model biases and improves the simulated life cycle of the CP-El Nino. Improved simulations of present day tropical seasonal variations and CP-El Nino events would increase the confidence in simulating their future behaviour.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 9
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    Unknown
    Wiley-Blackwell
    Publication Date: 2018-01-11
    Description: No abstract is available for this article.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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  • 10
    Publication Date: 2017-12-14
    Description: The Ozone Mapping and Profiler Suite (OMPS) is one of five instruments onboard the Suomi National Polar-orbiting Partnership (SuomiNPP) satellite. As part of OMPS, the Nadir Profiler (NP) spectrometer measures earth's albedo in ultraviolet wavelengths from 250 to 310 nm to profile earth atmospheric ozone concentration. Since launch in 2011, many changes in the NP radiometric and spectrometric calibration have been made to improve sensor data quality. The most challenging issue is to characterize instrument on-orbit spectral calibration and to maintain a stable spectral performance to meet sensor design criteria. Validation of the NP sensor data found an average of 3-5% error in the sensor albedo measurements that exceeded 2% requirement, creating 1-2% uncertainty in ozone profile. Data analysis attributes the error to pre-launch calibration uncertainty, ground-to-orbit dichroic changes, and on-orbit detector wavelength registration drifts. A recent update of calibration significantly improved spectral wavelength knowledge as well as the accuracy of the measured solar spectra. As a result, the wavelength-dependent albedo error is significantly reduced and generally meets the radiometric uncertainty requirement of 2%.
    Electronic ISSN: 2333-5084
    Topics: Geosciences , Physics
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