Higher Reflectance Values Research Articles

Prediction of simultaneous enhancement of Goos-Hänchen shift and reflectance in VO2 grating structure

Vanadium dioxide (VO2) material stands out in the family of the phase change materials due to its temperature-dependent phase transition properties, which make it a promising candidate for the temperature-dependent optoelectronic devices. Enhancement of the Goos-Hänchen (GH) shift is essential in VO2-based nanostructures for their applications, but it has been limited to the multilayered structures with VO2 materials so far. Here, we theoretically investigate the GH shift and corresponding reflectance in the VO2-based grating structure. We evidence that this structure has two GH peaks (3107λ and 2266λ) and high reflectance values (both up to 1) when VO2 is in the insulating phase as well as the maximum GH valley (−1061λ) and low reflectance (0.19) when VO2 is in the metallic phase. The electromagnetic field distributions in this hybrid structure suggest that the guided mode resonances (GMRs) can be excited no matter whether VO2 is in its insulating or metallic phases due to the couplings between the incident waves and the adjacent evanescent diffracted order waves, which produces their enhanced GH shifts. Different from the former case with the high reflectances and the large GH shifts, the latter has the low maximum magnetic field intensity due to the lossy property of the metallic VO2, which leads to the low reflectance and small GH valley value. Additionally, we have also found that by the alterations of the temperature-dependent conductivity of VO2 and the geometric parameters of the structure allows for the control the magnitude and position of the GH peak or valley. The simultaneously enhanced GH shifts and reflectances in the VO2-based grating structure, associated with its controllable features, enable it an effective configuration for establishing the temperature sensors and optoelectronic switches.

Habitat-driven otolith shape morphology in Oreochromis niloticus (pelagic) and Chrysichthys nigrodigitatus (benthic) from distinct zones of a tropical coastal lagoon system

This study explored the morpho-functional variations in the otoliths of Oreochromis niloticus (ON) and Chrysichthys nigrodigitatus (CN) across the Ikorodu (IKL) and Epe (EPL) regions in Nigeria's southern coastal lagoon system, with monthly sampling over twelve months. Digitized otoliths provided shape descriptors, and bathymetric analysis was conducted using the depth invariance index (DII). Remotely sensed reflectance (RSR) at 469 nm, 531 nm, and 555 nm assessed habitat productivity. Morpho-functional variations were evaluated using discriminant analysis (DA) and principal component analysis (PCA). Bathymetric analysis revealed that EPL has a deeper and more heterogeneous substratum than IKL. Additionally, Epe exhibited consistently higher RSR values than IKL. Sediment analysis showed higher clay and silt percentages in IKL and increased coarse sand in EPL, indicating distinct terrains. DA accuracy was high (ON: 92.0 %, CN: 90.8 % in cross-validation), highlighting variables such as area and circumference for ON and area, circularity, and compactness for CN. DA emphasized ellipticity, rectangularity, and roundness for ON, and form factor, compactness, circularity, and aspect ratio for CN. Higher reflectance values at EPL than at IKL indicate distinct ecological characteristics, with greater nutrient cycling and trophic productivity at EPL. Sediment analysis revealed distinct ecological heterogeneity and hydrological effects, with finer sediments in IKL indicating calmer conditions and EPL exhibiting higher energy conditions. Visualizing normal curve distributions for otolith shape descriptors in ON and CN populations revealed skewness patterns indicative of divergent adaptive features, possibly associated with habitat heterogeneity and productivity. The key otolith variables identified by DA and PCA suggest relative ecological opportunity and underscore the intricate relationships between otolith morphology and habitat variables (heterogeneity, productivity, sediment profile) in Nigeria's tropical southern lagoon system.

Near-infrared reflective coatings based on red-brown Ce1-xPrxO2 pigments

Red-brown Ce1-xPrxO2 pigments have high reflectance values over the entire NIR range, which recommend their use as NIR-reflective (cool) pigments. Ce0.99Pr0.01O2 pigment had the highest proportion of red and the lowest proportion of yellow (CIEL*/a*/b* = 60.1/19.7/13.1), corroborated with a total solar reflectance of 54.1 %. The pigments based on Ce1-xPrxO2 showed excellent behavior both in coloring an aqueous acrylic paint applied onto a metal substrate and a transparent glaze applied on a ceramic tile. The tile glazed with the Ce0.99Pr0.01O2 pigment had a significantly higher total solar reflectance (TSR = 45.0 %) than a commercial reference ceramic tile (TSR = 24.2 %), whilst the color of the two was comparable. In the case of metal substrates, the maximum temperature measured on the surface of the acrylic coating based on Ce1-xPrxO2 (54.0 °C) having a total solar reflectance of 51.4 %, was almost 10 °C lower than the temperature measured on the surface of the reference coating (63.7 °C), having a total solar reflectance of 35.7 %. These results demonstrate the extraordinary potential of Ce1-xPrxO2-based pigments to prevent overheating of metal/ceramic surfaces exposed to NIR radiation including, but not limited to, roofing applications.

Computational analysis of AlXSnSe4 (X = Ag and Cu) quaternary compounds: Uncovering first-principles insights into electronic structure, optical, and thermoelectric nature

Employing the recognized density functional theory, here we studied the multifaceted interactions of the structural, electrical, optical, and transport nature of new direct band gap AlXSnSe4 (X = Ag and Cu) quaternary materials. Significant band overlap between the electronic states of Tot-Ag and Tot-Se suggests that these two systems have strong bonding properties. The minima and maxima of the conduction band and valence band are located at the high symmetry Gamma-point in the first Brillouin zone which suggests a good behavior for optoelectronic devices. There exists a clear correlation between the dipole inter-band transition probability and the value of the real component of the dielectric constant. The highest absorption peaks are found in the ultraviolet spectrum, indicating that these materials are effective absorbers of the low- and medium-UV radiation. The high reflectivity values for both materials varied between 4.0 eV and 13.5 eV as photon energy increased. The considered materials are also suitable to be used in thermoelectric applications, that is confirmed from their significant and notable thermoelectric features.

First-principles calculations to investigate the physical properties of lead-free double perovskites Cs2AgXCl6 (X=P, Co, As, Cd) for optoelectronic applications

In this work, we have been systematically studied the structural, electronic, optical, mechanical, and thermodynamic properties of double perovskite Cs2AgXCl6 (X= P, Co, As, Cd) by adopting first-principles calculations based on density functional theory (DFT). We found that the determined lattice parameters are in good agreement with the previously reported study, which are 7.518558 Å, 7.491051 Å, 7.370192 Å, and 7.517199 Å for Cs2AgAsCl6, Cs2AgCdCl6, Cs2AgCoCl6, and Cs2AgPCl6, respectively. The negative result of formation energy (ΔHf) indicates that these compounds are thermodynamically stable and can be experimentally synthesized. The electronic energy band structure indicates that Cs2AgXCl6 (X=P, Co, As, Cd) compounds are semiconductor behavior with the band gap (Eg) of 1.047 eV, 1.085 eV, 1.205 eV, and 2.074 eV for Cs2AgPCl6, Cs2AgCoCl6, Cs2AgAsCl6, and Cs2AgCdCl6, respectively. Electronic properties suggest that carrier transport is enhanced in Cs2AgXCl6 (X=P, Co, As, Cd) because of holes and electrons' small effective mass. Furthermore, optical properties suggest that these compounds have high absorption coefficients and low reflectivity values in the visible region. The structural and thermodynamic stability, the obtained energy band gap, tunable optical properties, and interesting thermodynamic properties indicate that Cs2AgXCl6 (X=P, Co, As, Cd) is a potential candidate in photovoltaic and optoelectronic applications.

Machine Learning in the Hyperspectral Classification of Glycaspis brimblecombei (Hemiptera Psyllidae) Attack Severity in Eucalyptus

Assessing different levels of red gum lerp psyllid (Glycaspis brimblecombei) can influence the hyperspectral reflectance of leaves in different ways due to changes in chlorophyll. In order to classify these levels, the use of machine learning (ML) algorithms can help process the data faster and more accurately. The objectives were: (I) to evaluate the spectral behavior of the G. brimblecombei attack levels; (II) find the most accurate ML algorithm for classifying pest attack levels; (III) find the input configuration that improves performance of the algorithms. Data were collected from a clonal eucalyptus plantation (clone AEC 0144—Eucalyptus urophilla) aged 10.3 months old. Eighty sample evaluations were carried out considering the following severity levels: control (no shells), low infestation (N1), intermediate infestation (N2), and high infestation (N3), for which leaf spectral reflectances were obtained using a spectroradiometer. The spectral range acquired by the equipment was 350 to 2500 nm. After obtaining the wavelengths, they were grouped into representative interval means in 28 bands. Data were submitted to the following ML algorithms: artificial neural networks (ANN), REPTree (DT) and J48 decision trees, random forest (RF), support vector machine (SVM), and conventional logistic regression (LR) analysis. Two input configurations were tested: using only the wavelengths (ALL) and using the spectral bands (SB) to classify the attack levels. The output variable was the severity of G. brimblecombei attack. There were differences in the hyperspectral behavior of the leaves for the different attack levels. The highest attack level shows the greatest distinction and the highest reflectance values. LR and SVM show better accuracy in classifying the severity levels of G. brimblecombei attack. For the correct classification percentage, the RL and SVM algorithms performed better, both with accuracy above 90%. Both algorithms achieved F-score values close to 0.90 and above 0.8 for Kappa. The entire spectral range guaranteed the best accuracy for both algorithms.

Light-specific wavelengths differentially affect the exploration rate, opercular beat, skin color change, opsin transcripts, and the oxi-redox system of the longsnout seahorse Hippocampus reidi

Light is a strong stimulus for the sensory and endocrine systems. The opsins constitute a large family of proteins that can respond to specific light wavelengths. Hippocampus reidi is a near-threatened seahorse that has a diverse color pattern and sexual dimorphism. Over the years, H. reidi's unique characteristics, coupled with its high demand and over-exploitation for the aquarium trade, have raised concerns about its conservation, primarily due to their significant impact on wild populations. Here, we characterized chromatophore types in juvenile and adult H. reidi in captivity, and the effects of specific light wavelengths with the same irradiance (1.20 mW/cm2) on color change, growth, and survival rate. The xanthophores and melanophores were the major components of H. reidi pigmentation with differences in density and distribution between life stages and sexes. In the eye and skin of juveniles, the yellow (585 nm) wavelength induced a substantial increase in melanin levels compared to the individuals kept under white light (WL), blue (442 nm), or red (650 nm) wavelengths. In addition, blue and yellow wavelengths led to a higher juvenile mortality rate in comparison to the other treatments. Adult seahorses showed a rhythmic color change over 24 h, the highest reflectance values were obtained in the light phase, representing a daytime skin lightening for individuals under WL, blue and yellow wavelength, with changes in the acrophase. The yellow wavelength was more effective on juvenile seahorse pigmentation, while the blue wavelength exerted a stronger effect on the regulation of adult physiological color change. Dramatic changes in the opsin mRNA levels were life stage-dependent, which may infer ontogenetic opsin functions throughout seahorses' development. Exposure to specific wavelengths differentially affected the opsins mRNA levels in the skin and eyes of juveniles. In the juveniles, skin transcripts of visual (rh1, rh2, and lws) and non-visual opsins (opn3 and opn4x) were higher in individuals under yellow light. While in the juvenile's eyes, only rh1 and rh2 had increased transcripts influenced by yellow light; the lws and opn3 mRNA levels were higher in juveniles' eyes under WL. Prolonged exposure to yellow wavelength stimulates a robust increase in the antioxidant enzymes sod1 and sod2 mRNA levels. Our findings indicate that changes in the visible light spectrum alter physiological processes at different stages of life in H. reidi and may serve as the basis for a broader discussion about the implications of artificial light for aquatic species in captivity.

Cloud Properties Derived From Airborne Cloud Radar Observations Collected in Three Climatic Regions

AbstractClouds observed by the airborne High‐Performance Instrumented Airborne Platform for Environmental Research (HIAPER) Cloud Radar (HCR) were classified into twelve categories, based on their convective/stratiform nature. Dimensional and convective cloud properties were analyzed in three climatic regions: The subtropical easterlies off the coast of California, the Southern Ocean, and the tropics surrounding Central America. The convective properties of the stratocumulus clouds in the subtropical easterlies are closely related to the degree of boundary layer decoupling. In regions of strong boundary layer coupling, convectivity and updrafts in the clouds are weak and precipitation is light. In regions where the boundary layer is more decoupled, convective properties increase together with cloud top altitudes and cloud depth. Cloud properties of stratocumulus and cumulus clouds over the Southern Ocean show similarities to those observed in the subtropics, but overall they are less convective, indicating a strongly coupled boundary layer. Sea surface temperatures are much lower and the development of clouds is driven by transient synoptic conditions rather than zonal ocean temperature gradients. Clouds observed over the tropical oceans are much more convective in nature. As in the two other regions, they are mostly shallow, but clouds in regions with high sea surface temperatures have high convectivity and reflectivity values and stronger updrafts. Some of them grow to extreme depths (>14 km) and widths (>500 km). They have strong and large updraft regions and are heavily precipitating throughout their life cycle as they transition from the convective to the stratiform stage.

High NIR Reflectance and Photocatalytic Ceramic Pigments Based on M-Doped Clinobisvanite BiVO4 (M = Ca, Cr) from Gels.

Clinobisvanite (monoclinic scheelite BiVO4, S.G.I2/b) has garnered interest as a wide-band semiconductor with photocatalyst activity, as a high NIR reflectance material for camouflage and cool pigments and as a photoanode for PEC application from seawater. BiVO4 exists in four polymorphs: orthorhombic, zircon-tetragonal, monoclinic, and scheelite-tetragonal structures. In these crystal structures, V is coordinated by four O atoms in tetrahedral coordination and each Bi is coordinated to eight O atoms from eight different VO4 tetrahedral units. The synthesis and characterization of doped bismuth vanadate with Ca and Cr are studied using gel methods (coprecipitated and citrate metal-organic gels), which are compared with the ceramic route by means of the UV-vis-NIR spectroscopy of diffuse reflectance studies, band gap measurement, photocatalytic activity on Orange II and its relation with the chemical crystallography analyzed by the XRD, SEM-EDX and TEM-SAD techniques. The preparation of bismuth vanadate-based materials doped with calcium or chromium with various functionalities is addressed (a) as pigments for paints and for glazes in the chrome samples, with a color gradation from turquoise to black, depending on whether the synthesis is by the conventional ceramic route or by means of citrate gels, respectively; (b) with high NIR reflectance values that make them suitable as fresh pigments, to refresh the walls or roofs of buildings colored with them; and (c) with photocatalytic activity.

Energy performance assessment of venetian blinds in south-oriented residential spaces in hot arid desert climates

Purpose Window shading has always been an effective technique to control the access of solar radiation; however, inappropriate selection of the shading technique, location and optical properties may lead to an increase in energy consumed for cooling and artificial lighting. Venetian blinds (VBs) are a type of adjustable shading devices that can be installed to the interior, exterior or in between glass panes of a window and that can be easily implemented in both new and existing buildings. This study aims to investigate the impact of three VB parameters: slat angle, reflectivity and location on the overall energy consumption of a residential space with a south-facing facade under the hot arid desert climate of Saudi Arabia’s capital, Riyadh. For the purpose of globalizing the findings, the same investigations were applied for two other cities of similar climates: Cairo, Egypt, and Arizona, the USA. Design/methodology/approach A test room was modelled for energy simulation, with a 20% window-to-wall ratio. A VB was assigned with alternatives of being located to the indoor, outdoor or in between double glass panes. High, medium and low reflectivity values were applied at each location at slat angle alternatives of 15°, 30°, 45°, 60°, 75° and 90°. Findings Results showed VB performance across slat angles, where up to 20.1% energy savings were achieved by mid-pane high reflectivity VBs in Riyadh, while the value exceeded 30% in case of being externally located. A similar performance pattern occurred in the other two cities of hot arid desert climates: Cairo and Arizona. Research limitations/implications The study is limited to VBs at a fixed position, with no upward movement for partial or full openness conditions. The effect of blind control and operation on performance, such as the amount and duration of openness/closure of the blind and changes in slat angle across time, in addition to VB automation, shall be investigated in a future study. Practical implications The better understanding of VB energy performance achieved would enhance a more rational selection of VBs, which would benefit the construction industry as it would assist designers, real estate developer companies, as well as end-users in the decision-making process and help to realize energy-efficient solutions in residential buildings. VB production entities would also benefit by manufacturing and promoting for energy-efficient products. Originality/value In this study, a matrix of combinations of three VB parameters was developed, and the effect of these combinations on the overall energy consumption of both artificial lighting and heating, ventilation and air conditioning (HVAC) systems was evaluated and compared to identify the combinations of higher efficiency. The literature showed that these three parameters were hardly investigated in a combined form and hardly assessed by considering the overall energy consumed by both artificial lighting and HVAC.

Development of structural colored TiO2 thin films by varied etching solutions

Currently, one of the most important problems is water scarcity due to increasing population and environmental factors. Humankind can overcome this problem by recycling polluted water. The structural colors obtained from photonic crystal structures draw attention with fadeless bright color, combined with low toxicity and eco-friendliness. In this study, different etching/anodizing processes were applied to obtain Fabry-Perot and Photonic Crystal Ti-TiO2 structures. Structural colors owing to the morphology of the anatase phase on the surface of the samples etched with hydrochloric, sulfuric, and hydrofluoric acid-based solutions were obtained. The structural color of the formation on the titanium surfaces is related to the Fabry-Perot structures, while variations were correlated with Photonic Crystal surface morphologies. Because the high reflectance values contributed to the structural color formation, the photocatalytic efficiency of the samples etched with acid-based solutions was found to be lower than the samples etched with basic sodium and potassium hydroxide solutions. High-efficiency structural color reactors can be obtained by shifting the reflected wavelength range from the absorption wavelength range of the pollution material.

Cost-Effective and Efficient Cool Nanopigments Based on Oleic-Acid-Surface-Modified ZnO Nanostructured

In this paper, as-synthesized and oleic acid (OA)-surface-treated zinc oxide (ZnO) nanocrystals were successfully synthesized and investigated for cool-nanopigment applications. ZnO nanocrystals were synthesized using the thermal decomposition method. The OA-surface-treated ZnO sample was obtained with an OA:ZnO ratio of 1:1. The structural, optical and morphological properties of the samples were characterized via X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV-VIS-NIR diffused reflectance spectroscopy (DRS) and field-emission scanning electron microscopy (FE-SEM) techniques. ZnO nanocrystals possess a well-known zincate phase of ZnO, as confirmed for the as-synthesized sample with a reduction in the integrity of the ZnO crystalline structure upon the application of the OA coating. XRD peaks broadening and decreasing in crystallite size were obtained upon the surface modification of the ZnO by OA. The average crystallite size decreased from 31.5 to 17.4 nm, and the surface area changed from 23.37 to 7.48 m2/g upon OA treatment. These changes were attributed to the well-capping of the ZnO nanoparticles by OA, and, furthermore, OA increased the dispersion of the nanoparticles. The optical band gap of the investigated samples demonstrated a blue shift from 3.06 eV to 3.22 eV upon treatment. Both samples showed high NIR reflectance (RNIR∗) values, which makes them well qualified for use as cool nanopigments. Additionally, the as-synthesized sample showed an RNIR∗ value higher than that of the treated sample.

In vitro hyperspectral analysis of tattoo dyes.

There is no method that can guarantee effective, quick, and noninvasive removal of tattoo dyes. Laser methods are considered to be the method of choice. In this study, an attempt was made to determine the in vitro spectral characteristics of selected dyes used in permanent makeup and tattoos and to analyze the obtained parameters in terms of laser treatments optimization. Hyperspectral analysis was performed to determine the spectral characteristics of the dye on the entire surface of the slide. Seven dyes used in permanent makeup and tattoos were analyzed in vitro. The maximum reflectance and the wavelength for a given dye were determined for the maximum reflectance in the studied wavelength range: 400-1000nm. The optical properties of the dyes were determined based on visible light imaging using camera. The maximum radiation reflectance ranges from 634 to 732nm for the tested dyes. Visually very similar colors may differ significantly in the wavelength for which the maximum absorption of the radiation occurs. White and yellow dyes are characterized by the highest reflectance value. The black dye is characterized by the lowest reflectance coefficient. Low reflectance of black dye results in more safe and effective removal treatments. The homogeneity of radiation absorption can be identified using methods of analysis and processing of images in visible light. Optimization of the wavelength of which the maximum absorption/reflectance of radiation occurs may allow us to increase the effectiveness of laser treatments for removing permanent makeup and tattoos.

Analysis of CYGNSS coherent reflectivity over land for the characterization of pan-tropical inundation dynamics

The monitoring of flood and wetland dynamics at global scale is hampered by several limitations, including a reduced data availability in tropical areas due to the presence of clouds affecting visible and infrared imagery, or low spatial and/or temporal resolutions affecting passive and active microwave Earth Observation (EO) data. As a consequence, surface water extent estimates and their temporal variations remain challenging especially in equatorial river basins. Global Navigation Satellite System Reflectometry (GNSS-R) L-band signals recorded onboard Cyclone GNSS (CYGNSS) mission, composed of 8 Low Elevation Orbit (LEO) satellites, provide information on surface properties at high temporal resolution from 2017 up to now. CYGNSS bistatic observations were analyzed for detecting permanent water and seasonal floodplains over the full coverage of the mission, from 40°S to 40°N. We computed CYGNSS reflectivity associated to the coherent component of the received power, that was gridded at 0.1° spatial resolution with a 7-day time sampling afterwards. Several statistical metrics were derived from CYGNSS reflectivity, including the weighted mean and standard deviation, the median and the 90th percentile (respectively Γmean,Γstd,Γmedian and Γ90%) in each pixel. These parameters were clustered using the K-means algorithm with an implementation of the Dynamic Time Warping (DTW) similarity measure. They were compared to static inundation maps, and to dynamic estimations of surface water extent both at the global and regional scales, using the Global Inundation Extent from Multi-Satellites (GIEMS) and MODIS-based products. The difference between Γ90% and Γmedian shows the best sensitivity to the presence of water. The river streams and lakes are correctly detected, and a strong seasonality is identified in CYGNSS reflectivity over the largest floodplains, with the exception of the Cuvette Centrale of Congo which is covered by dense vegetation. This seasonal reflectivity signal correlates well with inundation maps: Pearson’s correlation coefficient between Γmedian and surface water extent from both GIEMS and MODIS is over 0.8 in the largest floodplains. The spatial patterns of reflectivity are consistent with static inundation maps: at the time of maximum flooding extent, a spatial correlation coefficient around 0.75 with Γmedian is obtained for several basins. We also evaluated the dependence of CYGNSS-derived clusters and reflectivity on the dominant land cover type and on the density of Above Groud Biomass (AGB) in the pixel. On the one hand, misclassifications of flooded pixels were observed over vegetated regions, probably due to uncertainties related to the attenuation by the vegetation in both CYGNSS and reference datasets. On the other hand, flooded pixels with a mean AGB up to ∼300 Mg/ha were correctly detected with the clustering. High reflectivity values are also observed over rocky soils in arid regions and create false alarms. Finally, strong winds on large lakes cause surface roughness, and lower reflectivity values are observed in this case which weaken the detection of open water. While these constraints are to be taken in account and corrected in a future model, a pan-tropical mapping of surface water extent dynamics using CYGNSS can be envisaged.

Geospatial assessment of 32-year changes in vegetation cover of some mangal-rainforest ecotone in parts of Asarama, Andoni, Rivers State.

The use of geospatial technologies, especially the GIS, has been helpful in monitoring and detecting changing patterns in various vegetation zones. The present study on Asarama study location site was on the basis that land use ecology of anthropogenic and natural influences have constantly led to changes in the vegetation ecotypes with attendant depletion and destruction in the study area. The study was aimed at evaluating the feasibility and use of geospatial tools in assessing these changes within the varying vegetation ecotypes (mangrove, ecotone and rainforest) spanning over 32 years at 16 -year intervals. Results of the 1986 Landsat imagery revealed maximum vegetal trend condition across the vegetation ecotypes that were impacted by anthropogenic activities (farming, logging, deforestation, road/bridge construction and urbanisation) with consequent vegetal cover change, loss and depletion as depicted in 2002 and 2018 Landsat imagery, exemplified in the normalised difference of vegetation index (NDVI) and normalised difference of build-up index (NDBE). The greener parts in the NDVI reflecting a higher value showing a healthy vegetal cover and the blue parts of NDBI with high reflectance values revealed areas of anthropogenic influence alterations. This, by implication, signifies the measure of the vegetation health condition and anthropogenic alteration, respectively.

Image muting of mixed precipitation to improve identification of regions of heavy snow in radar data

Abstract. In winter storms, enhanced radar reflectivity is often associated with heavy snow. However, some higher reflectivities are the result of mixed precipitation including melting snow. The correlation coefficient (a dual-polarization radar variable) can identify regions of mixed precipitation, but this information is usually presented separately from reflectivity. Especially under time pressure, radar data users can mistake regions of mixed precipitation for heavy snow because of the high cognitive load associated with comparing data in two fields while simultaneously attempting to discount a portion of the high reflectivity values. We developed an image muting method for regional radar maps that visually de-emphasizes the high reflectivity values associated with mixed precipitation. These image muted depictions of winter storm precipitation structures are useful for analyzing regions of heavy snow and monitoring real-time weather conditions.

Stratiform and Convective Rain Classification Using Machine Learning Models and Micro Rain Radar

Rain type classification into convective and stratiform is an essential step required to improve quantitative precipitation estimations by remote sensing instruments. Previous studies with Micro Rain Radar (MRR) measurements and subjective rules have been performed to classify rain events. However, automating this process by using machine learning (ML) models provides the advantages of fast and reliable classification with the possibility to classify rain minute by minute. A total of 20,979 min of rain data measured by an MRR at Das in northeast Spain were used to build seven types of ML models for stratiform and convective rain type classification. The proposed classification models use a set of 22 parameters that summarize the reflectivity, the Doppler velocity, and the spectral width (SW) above and below the so-called separation level (SL). This level is defined as the level with the highest increase in Doppler velocity and corresponds with the bright band in stratiform rain. A pre-classification of the rain type for each minute based on the rain microstructure provided by the collocated disdrometer was performed. Our results indicate that complex ML models, particularly tree-based ensembles such as xgboost and random forest which capture the interactions of different features, perform better than simpler models. Applying methods from the field of interpretable ML, we identified reflectivity at the lowest layer and the average spectral width in the layers below SL as the most important features. High reflectivity and low SW values indicate a higher probability of convective rain.

Microphysical and Kinematic Characteristics of Anomalous Charge Structure Thunderstorms in Cordoba, Argentina

Some thunderstorms in Cordoba, Argentina, present a charge structure with an enhanced low-level positive charge layer, and practically nonexistent upper-level positive charge. Storms with these characteristics are uncommon in the United States, even when considering regions with a high frequency of anomalous charge structure storms such as Colorado. In this study, we explored the microphysical and kinematic conditions inferred by radar that led to storms with this unique low-level anomalous charge structure in Argentina, and compared them to conditions conducive for anomalous and normal charge structures. As high liquid water contents in the mixed-phase layer lead to positive charging of graupel and anomalous storms through the non-inductive charging mechanism, we explored radar parameters hypothesized to be associated with large cloud supercooled liquid water contents in the mixed-phase layer and anomalous storms, such as mass and volume of hail and high-density graupel, large reflectivity associated with the growth of rimed precipitation to hail size, and parameters that are proxies for strong updrafts such as echo-top and Zdr column heights. We found that anomalous storms had higher values of mass and volume of hail in multiple sub-layers of the mixed-phase zone and higher frequency of high reflectivity values. Low-level anomalous events had higher hail mass in the lower portion of the mixed-phase zone when compared to normal events. Weaker updraft proxies were found for low-level anomalous events due to the shallow nature of these events while there was no distinction between the updraft proxies of normal and anomalous storms.

Assessing phosphorus nutritional status in maize plants using leaf-based hyperspectral measurements and multivariate analysis

ABSTRACT Remote sensing techniques have the potential to monitor physiological and biochemical changes caused by nutritional stress in plants. However, few studies have monitored the influence of foliar phosphorus levels on the spectral responses of plants, especially maize. This work aimed to assess phosphorus nutritional status in maize plants subjected to different sources and doses of phosphate fertilizer using leaf-based hyperspectral measurements and multivariate analysis. The specific goals addressed were a) the qualitative analysis of the spectral response, b) the identification of significant spectral wavelengths for differentiating doses of phosphate fertilizer, and c) the development of a spectral model for classifying the nutritional status of maize as an effective approach for crop nutritional assessment. Two experiments with different sources and doses of phosphate fertilizer were carried out: experiment 1 with monoammonium phosphate fertilizer (MAP) and experiment 2 with simple superphosphate fertilizer (SS). Hyperspectral reflectance (visible and near-infrared wavelengths) was collected at the V6 development stage of maize using an ASD Fieldspec 3 Jr Spectroradiometer, totalling 100 samples for each experiment. The collected data were submitted to principal component analysis (PCA) and linear discriminant analysis (LDA). The spectral signature of leaves showed higher reflectance values in the Vis spectral interval and lower reflectance in NIR under the absence of fertilization. For the other treatments, smaller differences in their spectral response were observed, especially for experiment 2. For experiment 1, the LDA achieved accuracy from 46 to 72% in the cross-validation step and from 50 to 75% in the external validation step. For experiment 2, the accuracy ranged from 25 to 82% in the cross-validation step and from 28 to 85% in the external validation step. In general, most misclassification was observed among treatments with similar fertilizer doses. These results suggest the potential of using hyperspectral data to monitor leaf P levels in maize, which contributes to the determination of crop management zones based on production variability under P limitation, in addition to optimizing the use of chemical inputs and guaranteeing greater sustainability of production systems.

Synthesis and structural, electrical, optical, and gamma-ray attenuation properties of ZnO-multi-walled carbon nanotubes (MWCNT) composite separately incorporated with CdO, TiO2, and Fe2O3

In this study, Fe2O3, TiO2, and CdO semiconductor metal oxides were separately incorporated into the ZnO-MWCNT composite at different weight percentages. Accordingly, several experimental analyses on electrical, optical, and radiation shielding characteristics of coupled semiconductor metal oxides nanocomposites were performed to determine their monotonic impact on the investigated material properties. Moreover, gamma-ray shielding properties of these novel materials were determined using MCNPX general-purpose Monte Carlo code. At 5% oxide addition, the maximum electrical conductivity was found in all groups for all temperatures. Moreover, 5% oxide reinforcement resulted in the maximum reflection characteristics in all groups. Among the CdO doped materials, the CZnOCd5 sample exhibits the highest electrical conductivity behaviour at room and high temperatures. The Eg value calculated for the CZnOCd5 sample was 3.284 eV. The CZnOCd2.5 and CZnOCd5 samples had the greatest Eg values when compared to the pure sample and the samples from other groups. The CZnOCd5 sample has the highest reflectance value in the CZnOCd group's reflectance graph. On the other hand, the maximum gamma-ray attenuation properties were reported for CZnOCd5 sample. Among the analysed samples, the CZnOCd5 sample's characteristics provide a preliminary motivation for a more comprehensive analysis of this material and assessment of potential radiation protection applications.