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  • 1
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    Minerals, Vol. 8, Pages 601: Carmeltazite, ZrAl2Ti4O11, a New Mineral Trapped in Corundum from Volcanic Rocks of Mt Carmel, Northern Israel (2018)
    MDPI
    In: Minerals
    Details
    Publication Date: 2018
    Description: The new mineral species carmeltazite, ideally ZrAl2Ti4O11, was discovered in pockets of trapped melt interstitial to, or included in, corundum xenocrysts from the Cretaceous Mt Carmel volcanics of northern Israel, associated with corundum, tistarite, anorthite, osbornite, an unnamed REE (Rare Earth Element) phase, in a Ca-Mg-Al-Si-O glass. In reflected light, carmeltazite is weakly to moderately bireflectant and weakly pleochroic from dark brown to dark green. Internal reflections are absent. Under crossed polars, the mineral is anisotropic, without characteristic rotation tints. Reflectance values for the four COM wavelengths (Rmin, Rmax (%) (λ in nm)) are: 21.8, 22.9 (471.1); 21.0, 21.6 (548.3), 19.9, 20.7 (586.6); and 18.5, 19.8 (652.3). Electron microprobe analysis (average of eight spot analyses) gave, on the basis of 11 oxygen atoms per formula unit and assuming all Ti and Sc as trivalent, the chemical formula (Ti3+3.60Al1.89Zr1.04Mg0.24Si0.13Sc0.06Ca0.05Y0.02Hf0.01)Σ=7.04O11. The simplified formula is ZrAl2Ti4O11, which requires ZrO2 24.03, Al2O3 19.88, and Ti2O3 56.09, totaling 100.00 wt %. The main diffraction lines, corresponding to multiple hkl indices, are (d in Å (relative visual intensity)): 5.04 (65), 4.09 (60), 2.961 (100), 2.885 (40), and 2.047 (60). The crystal structure study revealed carmeltazite to be orthorhombic, space group Pnma, with unit-cell parameters a = 14.0951 (9), b = 5.8123 (4), c = 10.0848 (7) Å, V = 826.2 (1) Å3, and Z = 4. The crystal structure was refined to a final R1 = 0.0216 for 1165 observed reflections with Fo 〉 4σ(Fo). Carmeltazite exhibits a structural arrangement similar to that observed in a defective spinel structure. The name carmeltazite derives from Mt Carmel (“CARMEL”) and from the dominant metals present in the mineral, i.e., Titanium, Aluminum and Zirconium (“TAZ”). The mineral and its name have been approved by the IMA Commission on New Minerals, Nomenclature and Classification (2018-103).
    Electronic ISSN: 2075-163X
    Topics: Geosciences
    Published by MDPI
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  • 2
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    Nitric Oxide Is a Volume Transmitter Regulating Postsynaptic Excitability at a Glutamatergic Synapse (2008)
    Cell Press
    Details
    Publication Date: 2008-11-01
    Print ISSN: 0896-6273
    Electronic ISSN: 1097-4199
    Topics: Biology , Medicine
    Published by Cell Press
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  • 3
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    Uniform shrub growth response to June temperature across the North Slope of Alaska (2018)
    Institute of Physics (IOP)
    Details
    Publication Date: 2018-03-28
    Description: The expansion of woody shrubs in arctic tundra alters many aspects of high-latitude ecosystems, including carbon cycling and wildlife habitat. Dendroecology, the study of annual growth increments in woody plants, has shown promise in revealing how climate and environmental conditions interact with shrub growth to affect these key ecosystem properties. However, a predictive understanding of how shrub growth response to climate varies across the heterogeneous landscape remains elusive. Here we use individual-based mixed effects modeling to analyze 19 624 annual growth ring measurements in the stems of Salix pulchra (Cham.), a rapidly expanding deciduous shrub. Stem samples were collected at six sites throughout the North Slope of Alaska. Sites spanned four landscapes that varied in time since glaciation and hence in soil properties, such as nutrient availability, that we expected would modulate shrub growth response to climate. Ring growth was remarkably coherent among site...
    Print ISSN: 1748-9318
    Electronic ISSN: 1748-9326
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering
    Published by Institute of Physics (IOP)
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  • 4
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    Arctic shrub growth trajectories differ across soil moisture levels (2017)
    Wiley
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    Publication Date: 2017-03-08
    Description: The circumpolar expansion of woody deciduous shrubs in arctic tundra alters key ecosystem properties including carbon balance and hydrology. However, landscape-scale patterns and drivers of shrub expansion remain poorly understood, inhibiting accurate incorporation of shrub effects into climate models. Here, we use dendroecology to elucidate the role of soil moisture in modifying the relationship between climate and growth for a dominant deciduous shrub, Salix pulchra , on the North Slope of Alaska, USA. We improve upon previous modeling approaches by using ecological theory to guide model selection for the relationship between climate and shrub growth. Finally, we present novel dendroecology-based estimates of shrub biomass change under a future climate regime, made possible by recently developed shrub allometry models. We find that S. pulchra growth has responded positively to mean June temperature over the past 2.5 decades at both a dry upland tundra site and an adjacent mesic riparian site. For the upland site, including a negative second-order term in the climate-growth model significantly improved explanatory power, matching theoretical predictions of diminishing growth returns to increasing temperature. A first-order linear model fit best at the riparian site, indicating consistent growth increases in response to sustained warming, possibly due to lack of temperature-induced moisture limitation in mesic habitats. These contrasting results indicate that S. pulchra in mesic habitats may respond positively to a wider range of temperature increase than S. pulchra in dry habitats. Lastly, we estimate that a 2°C increase in current mean June temperature will yield a 19% increase in aboveground S. pulchra biomass at the upland site and a 36% increase at the riparian site. Our method of biomass estimation provides an important link toward incorporating dendroecology data into coupled vegetation and climate models. This article is protected by copyright. All rights reserved.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
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  • 5
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    Methods for Comparing Simulated and Observed Satellite Infrared Brightness Temperatures and What Do They Tell Us? (2016)
    American Meteorological Society
    Details
    Publication Date: 2016-12-19
    Description: In this study, the utility of dimensioned, neighborhood-based, and object-based forecast verification metrics for cloud verification is assessed using output from the experimental High Resolution Rapid Refresh (HRRRx) model over a 1-day period containing different modes of convection. This is accomplished by comparing observed and simulated Geostationary Operational Environmental Satellite (GOES) 10.7-μm brightness temperatures (BTs). Traditional dimensioned metrics such as mean absolute error (MAE) and mean bias error (MBE) were used to assess the overall model accuracy. The MBE showed that the HRRRx BTs for forecast hours 0 and 1 are too warm compared with the observations, indicating a lack of cloud cover, but rapidly become too cold in subsequent hours because of the generation of excessive upper-level cloudiness. Neighborhood and object-based statistics were used to investigate the source of the HRRRx cloud cover errors. The neighborhood statistic fractions skill score (FSS) showed that displacement errors between cloud objects identified in the HRRRx and GOES BTs increased with time. Combined with the MBE, the FSS distinguished when changes in MAE were due to differences in the HRRRx BT bias or displacement in cloud features. The Method for Object-Based Diagnostic Evaluation (MODE) analyzed the similarity between HRRRx and GOES cloud features in shape and location. The similarity was summarized using the newly defined MODE composite score (MCS), an area-weighted calculation using the cloud feature match value from MODE. Combined with the FSS, the MCS indicated if HRRRx forecast error is the result of cloud shape, since the MCS is moderately large when forecast and observation objects are similar in size.
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 6
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    A Method for Calculating the Height of Overshooting Convective Cloud Tops Using Satellite-Based IR Imager and CloudSat Cloud Profiling Radar Observations (2016)
    American Meteorological Society
    Details
    Publication Date: 2016-02-01
    Description: Assigning accurate heights to convective cloud tops that penetrate into the upper troposphere–lower stratosphere (UTLS) region using infrared (IR) satellite imagery has been an unresolved issue for the satellite research community. The height assignment for the tops of optically thick clouds is typically accomplished by matching the observed IR brightness temperature (BT) with a collocated rawinsonde or numerical weather prediction (NWP) profile. However, “overshooting tops” (OTs) are typically colder (in BT) than any vertical level in the associated profile, leaving the height of these tops undetermined using this standard approach. A new method is described here for calculating the heights of convectively driven OTs using the characteristic temperature lapse rate of the cloud top as it ascends into the UTLS region. Using 108 MODIS-identified OT events that are directly observed by the CloudSat Cloud Profiling Radar (CPR), the MODIS-derived brightness temperature difference (BTD) between the OT and anvil regions can be defined. This BTD is combined with the CPR- and NWP-derived height difference between these two regions to determine the mean lapse rate, −7.34 K km−1, for the 108 events. The anvil height is typically well known, and an automated OT detection algorithm is used to derive BTD, so the lapse rate allows a height to be calculated for any detected OT. An empirical fit between MODIS and geostationary imager IR BT for OTs and anvil regions was performed to enable application of this method to coarser-spatial-resolution geostationary data. Validation indicates that ~75% (65%) of MODIS (geostationary) OT heights are within ±500 m of the coincident CPR-estimated heights.
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 7
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    Observations of Gravity Waves with High-Pass Filtering in the New Generation of Geostationary Imagers and Their Relation to Aircraft Turbulence (2018)
    American Meteorological Society
    Details
    Publication Date: 2018-01-24
    Description: This paper introduces a method of image filtering for viewing gravity waves in satellite imagery, which is particularly timely to the advent of the next-generation Advanced Himawari Imager (AHI) and the Advanced Baseline Imager (ABI). Applying a “high pass” filter to the upper-troposphere water vapor channel reveals sub-Kelvin-degree variations in brightness temperature that depict an abundance of gravity wave activity at the AHI/ABI sensitivity. Three examples demonstrate that this high-pass product can be exploited in a forecasting setting to identify possible varieties of turbulence-prone gravity waves that either 1) move roughly orthogonally to the apparent background flow or 2) produce interference as separate wave packets pass through the same location.
    Print ISSN: 0882-8156
    Electronic ISSN: 1520-0434
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 8
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    Seasonal Analysis of Cloud Objects in the High-Resolution Rapid Refresh (HRRR) Model Using Object-Based Verification (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-08-01
    Description: In this study, object-based verification using the method for object-based diagnostic evaluation (MODE) is used to assess the accuracy of cloud-cover forecasts from the experimental High-Resolution Rapid Refresh (HRRRx) model during the warm and cool seasons. This is accomplished by comparing cloud objects identified by MODE in observed and simulated Geostationary Operational Environmental Satellite 10.7-μm brightness temperatures for August 2015 and January 2016. The analysis revealed that more cloud objects and a more pronounced diurnal cycle occurred during August, with larger object sizes observed in January because of the prevalence of synoptic-scale cloud features. With the exception of the 0-h analyses, the forecasts contained fewer cloud objects than were observed. HRRRx forecast accuracy is assessed using two methods: traditional verification, which compares the locations of grid points identified as observation and forecast objects, and the MODE composite score, an area-weighted calculation using the object-pair interest values computed by MODE. The 1-h forecasts for both August and January were the most accurate for their respective months. Inspection of the individual MODE attribute interest scores showed that, even though displacement errors between the forecast and observation objects increased between the 0-h analyses and 1-h forecasts, the forecasts were more accurate than the analyses because the sizes of the largest cloud objects more closely matched the observations. The 1-h forecasts from August were found to be more accurate than those during January because the spatial displacement between the cloud objects was smaller and the forecast objects better represented the size of the observation objects.
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 9
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    Climatology of Tropical Overshooting Tops in North Atlantic Tropical Cyclones (2017)
    American Meteorological Society
    Details
    Publication Date: 2017-06-01
    Description: Organized tropical convection, often characterized by overshooting tops, is a distinguishing quality of tropical cyclones (TCs). In this study, the climatology of tropical overshooting tops (TOTs) in North Atlantic Ocean TCs from 2004 to 2015 is examined. Previous studies have investigated the distribution of convection in TCs based on lightning data. The purpose of this study is to examine the distribution of TC convection from geostationary satellites using an objective TOT detection algorithm based on infrared brightness temperatures and empirically dependent thresholds. It will be shown that TOTs can provide an additional metric for identifying the characteristics of TC convection. Based on the 12-yr (2004–15) climatology, a distinct semidiurnal cycle in TOT activity is detected within 500 km of the TC center. In agreement with lightning data from previous studies, a predawn maximum (local to the TC) in TOTs is observed within 300 km of the TC center. A second predusk maximum is associated with TOTs between 300 and 500 km of the TC center. TC intensity and intensity trend along with environmental factors can affect the number and distribution of TOTs. For example, an exponential relationship exists between the number of TOTs and increasing sea surface temperatures. Conversely, increasing vertical wind shear magnitude decreases the density of TOTs, with a higher percentage of TOTs observed downshear of the wind direction. Generally, within 100 km (100–300 km) of the TC center, the preferred quadrant for TOTs is downshear left (downshear right), and increased TOT activity is observed right of TC motion. The findings corroborate previous lightning study results while providing additional insights into TC convection.
    Print ISSN: 1558-8424
    Electronic ISSN: 1558-8432
    Topics: Geography , Physics
    Published by American Meteorological Society
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  • 10
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    Assessing the Impact of Stochastic Perturbations in Cloud Microphysics using GOES-16 Infrared Brightness Temperatures (2020)
    American Meteorological Society
    Details
    Publication Date: 2020-07-08
    Description: In this study, infrared brightness temperatures (BTs) are used to examine how applying stochastic perturbed parameter (SPP) methodology to the widely used Thompson–Eidhammer cloud microphysics scheme impacts the cloud field in high-resolution forecasts. Modifications are made to add stochastic perturbations to three parameters controlling cloud generation and dissipation processes. Two five-member ensembles are generated, one using the microphysics parameter perturbations (SPP-MP) and another where white noise perturbations were added to potential temperature fields at initialization time (Control). The impact of the SPP method was assessed using simulated and observed GOES-16 BTs. This analysis uses pixel-based and object-based methods to assess the impact on the cloud field. Pixel-based methods revealed that the SPP-MP BTs are slightly more accurate than the Control BTs. However, too few pixels with a BT lower than 270 K result in a positive bias compared to the observations. A negative bias compared to the observations is observed when only analyzing lower BTs. The spread of the ensemble BTs was analyzed using the continuous ranked probability score differences, with the SPP-MP ensemble BTs having less (more) spread during May (January) compared to the Control. Object-based analysis using the Method for Object-Based Diagnostic Evaluation revealed the upper-level cloud objects are smaller in the SPP-MP ensemble than the Control but a lower bias exists in the SPP-MP BTs compared to the Control BTs when overlapping matching objects. However, there is no clear distinction between the SPP-MP and Control ensemble members during the evolution of objects, Overall, the SPP-MP perturbations result in lower BTs compared to the Control ensemble and more cloudy pixels.
    Print ISSN: 0027-0644
    Electronic ISSN: 1520-0493
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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