Differential Reflectivity Research Articles

Observations of Diurnal Variability under the Cirrus Canopy of Typhoon Kong-rey (2018)

AbstractA growing body of work has documented the existence of diurnal oscillations in the tropical cyclone outflow layer. These diurnal pulses have been examined primarily using satellites or numerical models, and detailed full tropospheric observations or case study analyses of diurnal pulses are lacking. Questions remain on the vertical extent of diurnal pulses and whether diurnal pulses are coupled to convective bands or constrained to the outflow layer. During the Propagation of Intraseasonal Tropical Oscillations (PISTON) field campaign, diurnal oscillations in the upper-level clouds were observed during Typhoon Kong-rey’s (2018) rapid intensification. Over a 3.5 day period where a broad distribution of cold upper-level clouds was overhead, detailed observations of Typhoon Kong-rey’s rainbands show that convection had reduced echo tops but enhanced reflectivity and differential reflectivity aloft compared to other observations during PISTON. Shortwave heating in the upper-levels increased the stability profile in an overall favorable thermodynamic environment for convection during the day, which could help to explain the diurnal differences in convective structure. Under the cirrus canopy, nocturnal convection was deeper and daytime convection shallower in contrast to the rest of the PISTON dataset. Diurnal oscillations in the brightness temperatures were found to be coupled to radially outward propagating convective rainbands that were preceded ~6 hours by outflow jets. The cooling pulses occurred earlier than found in previous studies. The pulses were asymmetric spatially which is likely due to a combination of the vertical wind shear and storm intensity.

Efficient interlayer electron transfer in a MoTe2/WS2/MoS2 trilayer heterostructure

Electron transfer and carrier dynamics in MoTe2/WS2/MoS2 trilayer heterostructures are investigated by transient absorption and photoluminescence measurements. Monolayer flakes of MoTe2, WS2, and MoS2 are obtained by mechanical exfoliation from their bulk crystals and are used to fabricate the heterostructures by a dry-transfer technique. Photoluminescence spectroscopic measurements indicate that the recombination of the MoS2 and WS2 intralayer excitons is significantly suppressed in the heterostructure, illustrating the efficient interlayer charge transfer processes. Layer-selective time-resolved differential reflectance measurements show that the electrons excited in MoTe2 can transfer to MoS2 within 0.3 ps. The transferred electrons show a long lifetime of several hundred picoseconds due to their slow recombination with the spatially separated holes that reside in MoTe2. Furthermore, the charge transfer and recombination processes are weakly dependent on the injected carrier density. These results demonstrate the feasibility of constructing van der Waals multilayer heterostructures involving the infrared-sensitive MoTe2 with emergent properties and provide important information to quantify the performance of MoTe2-based devices.

Identification of snowfall microphysical processes from Eulerian vertical gradients of polarimetric radar variables

Abstract. Polarimetric radar systems are commonly used to study the microphysics of precipitation. While they offer continuous measurements with a large spatial coverage, retrieving information about the microphysical processes that govern the evolution of snowfall from the polarimetric signal is challenging. The present study develops a new method, called process identification based on vertical gradient signs (PIVSs), to spatially identify the occurrence of the main microphysical processes (aggregation and riming, crystal growth by vapor deposition and sublimation) in snowfall from dual-polarization Doppler radar scans. We first derive an analytical framework to assess in which meteorological conditions the local vertical gradients of radar variables reliably inform about microphysical processes. In such conditions, we then identify regions dominated by (i) vapor deposition, (ii) aggregation and riming and (iii) snowflake sublimation and possibly snowflake breakup, based on the sign of the local vertical gradients of the reflectivity ZH and the differential reflectivity ZDR. The method is then applied to data from two frontal snowfall events, namely one in coastal Adélie Land, Antarctica, and one in the Taebaek Mountains in South Korea. The validity of the method is assessed by comparing its outcome with snowflake observations, using a multi-angle snowflake camera, and with the output of a hydrometeor classification, based on polarimetric radar signal. The application of the method further makes it possible to better characterize and understand how snowfall forms, grows and decays in two different geographical and meteorological contexts. In particular, we are able to automatically derive and discuss the altitude and thickness of the layers where each process prevails for both case studies. We infer some microphysical characteristics in terms of radar variables from statistical analysis of the method output (e.g., ZH and ZDR distribution for each process). We, finally, highlight the potential for extensive application to cold precipitation events in different meteorological contexts.

Electrostatics of Single Monolayer Graphene Coated Metal Electrode in Electrolyte

AbstractUnlike metals, graphene forms a hydration layer at the electrode/electrolyte interface, which is unusual for a conducting material. Here, the electrostatic properties of the hydration layer are studied by measuring the oscillation of ions at the interface due to an applied AC potential by differential reflectivity during cyclic voltammetry (CV). The amplitude of ion oscillation at picometer range sensitivity on a partially coated Au electrode by a graphene monolayer reveals a remarkable difference between the coated and uncoated part of the electrode. The uncoated Au electrode exhibits the expected behavior, but the oscillation of ions is completely screened over the graphene coated electrode up to 0.2 M of NaCl. The “insulating” behavior is consistent with CV and DPV. The behavior attributed to the hydration layer could be reversibly disrupted to de‐screen the electric field to study the electrostatics of graphene/Au interface. The shift in Fermi level of hydration‐layer‐free graphene/Au relative to Au is quantitatively consistent with work function transparency of graphene. The cut‐off of the emanating field from the underlying electrode in an electrolyte is another example of graphene's unique passivation property that will have profound effect on applications such as, supercapacitors where the charge state of interface is critical.

Optical properties of Pb0.52Zr0.48TiO3 nanorod arrays: second harmonic generation and multiphoton carrier dynamics

Nonlinear optical properties of poled and unpoled, lead zirconate-titanate (Pb0.52Zr0.48TiO3) nanorod arrays, grown on Pt-coated Si with ∼200 nm diameter and ∼600 nm height, were investigated. Clear signatures of second harmonic generations (SHG), from 490–525 nm (2.38–2.53 eV) at room temperature, were observed. Furthermore, time resolved differential reflectivity measurements were performed to study dynamical properties of photoexcited carriers in the range of 690–1000 nm where multiphoton processes were responsible for the photo-excitations. We compared this excitation scheme, which is sensitive mainly to the surface states, to when the photoexcited energy (∼3.1 eV) was close to the band gap of the nanorods. Our results offer promises for employing these nanostructures in nonlinear photonic applications.

Observed Bulk Hook Echo Drop Size Distribution Evolution in Supercell Tornadogenesis and Tornadogenesis Failure

AbstractThe time preceding supercell tornadogenesis and tornadogenesis “failure” has been studied extensively to identify differing attributes related to tornado production or lack thereof. Studies from the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) found that air in the rear-flank downdraft (RFD) regions of non- and weakly tornadic supercells had different near-surface thermodynamic characteristics than that in strongly tornadic supercells. Subsequently, it was proposed that microphysical processes are likely to have an impact on the resulting thermodynamics of the near-surface RFD region. One way to view proxies to microphysical features, namely drop size distributions (DSDs), is through use of polarimetric radar data. Studies from the second VORTEX used data from dual-polarization radars to provide evidence of different DSDs in the hook echoes of tornadic and non-tornadic supercells. However, radar-based studies during these projects were limited to a small number of cases preventing result generalizations. This study compiles 68 tornadic and 62 non-tornadic supercells using Weather Surveillance Radar–1988 Doppler (WSR-88D) data to analyze changes in polarimetric radar variables leading up to, and at, tornadogenesis and tornadogenesis failure. Case types generally did not show notable hook echo differences in variables between sets, but did show spatial hook echo quadrant DSD differences. Consistent with past studies, differential radar reflectivity factor (ZDR) generally decreased leading up to tornadogenesis and tornadogenesis failure; in both sets, estimated total number concentration increased during the same times. Relationships between DSDs and the near-storm environment, and implications of results for nowcasting tornadogenesis, also are discussed.

Microphysical and Polarimetric Radar Modeling of Hydrometeor Refreezing

AbstractA unique polarimetric radar signature indicative of hydrometeor refreezing during ice pellet events has been documented in several recent studies, yet the underlying microphysical causes remain unknown. The signature is characterized by enhancements in differential reflectivity (ZDR), specific differential phase (KDP), and linear depolarization ratio (LDR), and a reduction in copolar correlation coefficient (ρhv) within a layer of decreasing radar reflectivity factor at horizontal polarization (ZH). In previous studies, the leading hypothesis for the observed radar signature is the preferential refreezing of small drops. Here, a simplified, one-dimensional, explicit bin microphysics model is developed to simulate the refreezing of fully melted hydrometeors, and coupled with a polarimetric radar forward operator to quantify the impact of preferential refreezing on simulated radar signatures. The modeling results demonstrate that preferential refreezing is insufficient by itself to produce the observed signatures. In contrast, simulations considering an ice shell growing asymmetrically around a freezing particle (i.e., emulating a thicker ice shell on the bottom of a falling particle) produce realistic ZDR enhancements, and also closely replicate observed features in ZH, KDP, LDR, and ρhv. Simulations that assume no increase in particle wobbling with freezing produce an even greater ZDR enhancement, but this comes at the expense of reducing the LDR enhancement. It is suggested that the polarimetric refreezing signature is instead strongly related to both the distribution of the unfrozen liquid portion within a freezing particle and the orientation of this liquid with respect to the horizontal.

Communication-In Situ Differential Reflectance Spectroscopy Monitoring the Asynchronous Transient Response at the Edge and Center of the Disk Electrode

The asynchronous transient responses at the edge and center of a gold disk electrode are monitored by in situ differential reflectance spectroscopy (DRS). The DRS spectrum collected in 10 mM perchloric acid shows that the edge of the electrode achieves the equilibrium sooner than the center does in chronoamperometry, which establishes the foundation for a similar electrochemical protocol to remove the metallic Cu at the edge of a Cu/Au disk electrode while keeping these at the center intact. Both phenomena are caused by the larger resistance at the center than the edge of a disk electrode.

Photodegradation of reactive blue 19 dye using magnetic nanophotocatalyst α-Fe2O3/WO3: A comparison study of α-Fe2O3/WO3 and WO3/NaOH

The photocatalytic degradation of reactive blue 19 (RB19) dye was investigated in a slurry system using ultraviolet (UV) and light-emitting diode (LED) lamps as light sources and using magnetic tungsten trioxide nanophotocatalysts (α-Fe2O3/WO3 and WO3/NaOH) as photocatalysts. The effects of different parameters including irradiation time, initial concentration of RB19, nanophotocatalyst dosage, and pH were examined. The magnetic nanophotocatalysts were also characterized with different methods including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL), differential reflectance spectroscopy (DRS), Fourier transform infrared spectroscopy (FTIR), and vibrating sample magnetometry (VSM). The XRD and FTIR analyses confirmed the presence of tungsten trioxide on the iron oxide nanoparticles. The VSM analysis confirmed the magnetic ability of the new synthesized nanophotocatalyst α-Fe2O3/WO3 with 39.6 emu/g of saturation magnetization. The reactor performance showed considerable improvement in the α-Fe2O3-modified nanophotocatalyst. The impact of visible light was specifically investigated, and it was compared with UV-C light under the same experimental conditions. The reusability of the magnetic nanophotocatalyst α-Fe2O3/WO3 was tested during six cycles, and the magnetic materials showed an excellent removal efficiency after six cycles, with just a 7% decline.

Evaluation of Bias Correction Methods for Improving Weather Radar-based Rainfall Estimation

This study focused on the reflectivity measurement bias (Z-bias) and the rainfall bias (R-bias) in the radar-rainfall estimation process. To correct the Z-bias, the self-consistency constraint method using reflectivity, differential reflectivity, and specific differential phase was carried out. Then, the Mean Field Bias Correction (MFBC) method and the Local Gauge Correction (LGC) method, were conducted to correct the R-bias. All of correction methods were applied to the Radar-AWS Rainrate model to calculate radar-rainfall estimates. The accuracy of the Z-bias correction method in 18 rainfall cases was improved by considering the RMSE (from 7.37 to 7.21 mm/hr) and the Correlation Coefficient (CC) (from 0.83 to 0.84) on average. The accuracy of results in the Changma and local torrential cases was improved by applying the Z-bias correction. The accuracy obtained by the LGC method (by 63.7% in RMSE and 11.7% in CC compared to MFBC) was superior to the MFBC method results because, in the LGC method, different R-biases were applied to each rainfall estimates in each radar pixel.

Green synthesis of dimanganese trioxide nanoparticles using tamarind seed powder: Effect of tamarind seed powder concentration on the structural, electrical and electrochemical properties of dimanganese trioxide nanoparticles

In Rechargeable Battery, anode electrode plays a crucial role as it directly influences the electrochemical performance (High power and energy). This leads to synthesize a novel anode electrode material. Manganese oxide is one of the prominent transition metal oxides. Hence in the present work Dimanganese trioxide (Mn2O3) nanoparticles are synthesized using Green combustion synthesis process. Manganese (II) nitrate tetrahydrate is used as precursor and Tamarind seed powder is used as fuel in the synthesis process. Precursor weight is kept constant and fuel concentration is varied as 0.1 g, 0.2 g and 0.3 g. The precursor and fuel are mixed and calcinated at 700 °C to produce Mn2O3 nanoparticles. The Structural, Electrical and Electrochemical properties of the synthesized Mn2O3 nanoparticles are studied using XRD (X-ray diffraction), FTIR (Fourier Transform Infrared), SEM (Scanning Electron microscopy) and TEM (Transmission Electron Microscopy), UVDRS (Ultraviolet Differential Reflectance Spectroscopy), EIS (Electrochemical Impedance Spectroscopy) and BET (Brunauer-Emmett-Teller). XRD result confirms that the synthesized Mn2O3 nanoparticles are highly crystalline with cubic structure. The FTIR spectrum is drawn from (400 to 4000)cm−1. The FTIR peaks in the range of (490 to 600cm−1) correlates to Mn-O bending vibrations. The study of SEM images of synthesized Mn2O3 nanoparticles depicts the porous material. Interplanar distance is analyzed using TEM images and is found to be 0.21 nm for sample with 0.2 g fuel concentration. The study of UVDRS analysis gives the band gap ranging from 1.30 eV to 1.36 eV. EIS of the synthesized Mn2O3 nanoparticles gives the impedance in the range from 274.6 Ω to 323.8 Ω. The BET results confirm the sample Mn200 is of Type-II isotherm with the specific surface area about 2.4862 m2 /g. The Mn2O3 nanoparticles prepared using 0.2 g fuel concentration exhibit improved Structural, Electrical and Electrochemical properties. Hence these nanoparticles may be used as electrode material in rechargeable batteries.

Mobile Ka-Band Polarimetric Doppler Radar Observations of Wildfire Smoke Plumes

ABSTRACTRemote sensing techniques have been used to study and track wildfire smoke plume structure and evolution; however, knowledge gaps remain because of the limited availability of observational datasets aimed at understanding fine-scale fire–atmosphere interactions and plume microphysics. Meteorological radars have been used to investigate the evolution of plume rise in time and space, but highly resolved plume observations are limited. In this study, we present a new mobile millimeter-wave (Ka band) Doppler radar system acquired to sample the fine-scale kinematics and microphysical properties of active wildfire smoke plumes from both wildfires and large prescribed fires. Four field deployments were conducted in autumn of 2019 during two wildfires in California and one prescribed burn in Utah. Radar parameters investigated in this study include reflectivity, radial velocity, Doppler spectrum width, differential reflectivity ZDR, and copolarized correlation coefficient ρHV. Observed radar reflectivity ranged between −15 and 20 dBZ in plume, and radial velocity ranged from 0 to 16 m s−1. Dual-polarimetric observations revealed that scattering sources within wildfire plumes are primarily nonspherical and oblate-shaped targets as indicated by ZDR values measuring above 0 and ρHV values below 0.8 within the plume. Doppler spectrum width maxima were located near the updraft core region and were associated with radar reflectivity maxima.

Polarimetric Radar Characteristics of Tornadogenesis Failure in Supercell Thunderstorms

Many nontornadic supercell storms have times when they appear to be moving toward tornadogenesis, including the development of a strong low-level vortex, but never end up producing a tornado. These tornadogenesis failure (TGF) episodes can be a substantial challenge to operational meteorologists. In this study, a sample of 32 pre-tornadic and 36 pre-TGF supercells is examined in the 30 min pre-tornadogenesis or pre-TGF period to explore the feasibility of using polarimetric radar metrics to highlight storms with larger tornadogenesis potential in the near-term. Overall the results indicate few strong distinguishers of pre-tornadic storms. Differential reflectivity (ZDR) arc size and intensity were the most promising metrics examined, with ZDR arc size potentially exhibiting large enough differences between the two storm subsets to be operationally useful. Change in the radar metrics leading up to tornadogenesis or TGF did not exhibit large differences, though most findings were consistent with hypotheses based on prior findings in the literature.

Physical and electrochemical behavior of black nickel coatings in presence of KNO3 and imidazole additives

As a unique type of nickel films, black nickel coatings possess remarkable optical and electrical properties but limited applications owing to their poor structure and corrosion resistance. In this study, black nickel coatings were electrodeposited on St37 steel and optimized utilizing nickel Watts bath modified with potassium nitrate. By investigating the coating structure and current efficiency (CE), optimum bath was determined as 190 g/L NiSO4, 25 g/L NiCl2, 30 g/L H3BO3, and 25 g/L KNO3 which resulted in CE of 79% and a compact structure. Next, cyclic voltammetry and chronoamperometric tests revealed that the dominant deposition mechanism was instantaneous nucleation. Besides studying the changes in CE and cathodic polarization, the improvement of properties with addition of imidazole was investigated by studying the surface morphology, phase structure, light absorption, and corrosion behavior using SEM, XRD, differential reflectance spectroscopy (DRS), potentiodynamic polarization, and electrochemical impedance spectroscopy tests, respectively. Adding imidazole to the deposition bath reduced the grain size and crack width from micro-scale to nano-scale, without affecting its nucleation mechanism or light absorption property. Also, imidazole enhanced the corrosion resistance of the black nickel coatings by 62% reduction of corrosion current density and increasing its polarization resistance by 58%.

All-optical control of charge transfer and interlayer excitons in transition metal dichalcogenide heterostructures

An all-optical approach to control interlayer charge transfer and interlayer exciton dynamics is demonstrated using transition metal dichalcogenide heterostructures of ${\mathrm{MoSe}}_{2}/{\mathrm{MoS}}_{2}$ and ${\mathrm{MoSe}}_{2}/{\mathrm{WS}}_{2}$ as examples. In the three-pulse pump-probe experiments, a control pulse injects photocarriers and produces an electric field due to the interlayer charge separation. A pump pulse excites new carriers and their dynamics under the influence of the control-injected carriers and field is time-resolved by measuring differential reflectance of a third probe pulse. In ${\mathrm{MoSe}}_{2}/{\mathrm{MoS}}_{2}$, the interlayer electron transfer time from ${\mathrm{MoSe}}_{2}$ to ${\mathrm{MoS}}_{2}$ decreases with increasing the control-injected carrier density and electric field. The dipole moment of the interlayer excitons is reduced by the control pulse, which can be utilized for ultrafast and all-optical control of interlayer excitons. The recombination of the interlayer excitons is enhanced by the control pulse, which increases the spatial overlap of the electron and hole wave functions. The effect of the control pulse on the interlayer excitons is confirmed in the ${\mathrm{MoSe}}_{2}/{\mathrm{WS}}_{2}$ heterostructure, although its effect on the electron transfer time is not resolvable. These results reveal useful information to understand and control interlayer charge transfer dynamics and provide tools for ultrafast manipulation of electrons in van der Waals heterostructures.

Investigation of Cloud-to-Ground Flashes in the Non-Precipitating Stratiform Region of a Mesoscale Convective System on 20 August 2019 and Implications for Decision Support Services

AbstractInfrequent lightning flashes occurring outside of surface precipitation pose challenges to Impact-Based Decision Support Services (IDSS) for outdoor activities. This paper examines the remote sensing observations from an event on 20 August 2019 where multiple cloud-to-ground flashes occurred over 10 km outside surface precipitation (lowest radar tilt reflectivity < 10 dBZ and no evidence of surface precipitation) in a trailing stratiform region of a mesoscale convective system. The goal is to demonstrate the fusion of radar with multiple lightning observations and a lightning risk model to demonstrate how reflectivity and differential reflectivity combined provided the best indicator for the potential of lightning where all of the other lightning safety methods failed. A total of 13 lightning flashes were observed by the Geostationary Lightning Mapper (GLM) within the trailing stratiform region between 2100 and 2300 UTC. The average size of the 13 lightning flashes was 3184 km2, with an average total optical energy of 7734 fJ. A total of 75 NLDN flash locations were coincident with the 13 GLM flashes, resulting in an average of 5.8 NLDN flashes [in-cloud (IC) and cloud-to-ground (CG)] per GLM flash. In total, five of the GLM flashes contained at least one positive cloud-to-ground flash (+CG) flash identified by the NLDN, with peak amplitudes ranging between 66 and 136 kA. All eight CG flashes identified by the NLDN were located more than 10 km outside surface precipitation. The only indication of the potential of these infrequently large flashes was the presence of depolarization streaks in differential reflectivity (ZDR) and enhanced reflectivity near the melting layer.

A microprocessor-aided platform enabling surface differential reflectivity and reflectance anisotropy spectroscopy

Surface differential reflectivity (SDR) and reflectance anisotropy spectroscopy (RAS) [sometimes known as reflectance difference spectroscopy] are two well-known optical spectroscopies used in the investigation of surfaces and interfaces. Their adaptability on different experimental conditions (vacuum, controlled atmosphere and liquid environment) allows for the investigation not only of surface states and/or ultra-thin films but also of more complex interfaces. In these circumstances, the analysis of the sample with both techniques is decisive in view of obtaining a correct picture of the sample optical properties. In this work, we show a microelectronic hardware solution useful to control both a SDR and a RAS apparatus. We describe an electronic architecture that can be easily replicated, and we applied it to a representative sample where the interpretation of the optical properties requires an analysis by both SDR and RAS.Graphic abstract

Facile synthesis of efficient heterogeneous photocatalytic and highly dielectric Bi4BaTi4O15 ceramic with remarkable applicability in the degradation of rhodamine B dye

ABSTRACT Bi4BaTi4O15(BBTO), an Aurivillius oxide, which is a mixed metal bismuth–layered based oxide fabricated by chemical route, has shown highly efficient photocatalytic activity in degradation of organic dye besides possessing high dielectric constant. The obtained material was characterised by various techniques like Fourier Transform Infrared (FTIR), transmission electron microscope, Scanning Electron Microscopy-Energy Dispersive X-rays Spectroscopy (SEM-EDX) X-ray powder diffraction (XRD), Zetasizer Nano-ZS, Ultraviolet- differential reflectance spectroscopy (UV-DRS), Brunauer–Emmett–Teller, Atomic Force Microscopy (AFM) and X-ray photoelectron spectra for the phase identification, microstructural analysis, bandgap determination, elemental analysis and oxidation state of the material. XRD data confirm the presence of single-phase BBTO ceramic, corroborated by Le-Bail fitting analysis. A high dielectric constant value of 3.08 × 103 was obtained for the BBTO ceramic at 368 K. The material is stable in suspension form in solution and is a highly efficient photocatalyst. BBTO degraded 80% of RhB dye within 1 h of time period under UV light via major reactive species OH . radicals and O2 .- , generated during the photocatalytic reaction, which is proved to be following the first-order kinetics.

Photocatalytic removal of naphthalene (C10H8 ) from aqueous environments using sulfur and nitrogen doped titanium dioxide (TiO2 -N-S) coated on glass microbullets in presence of sunlight

Background and aims: Due to their toxicity and carcinogenic effects, polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (C10H8 ) are regarded as hazardous compounds for both humans and the environment, and it is essential to remove these contaminants from the environment. The present study aimed to remove naphthalene from a synthetic aqueous environment using sulfur and nitrogen doped titanium dioxide (TiO2 -N-S) nanoparticles (NPs) immobilized on glass microbullets under sunlight. Methods: In this experimental study, TiO2 -N-S NPs were synthesized using sol-gel process. The structure of NPs was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and differential reflectance spectroscopy (DRS). In addition, using statistical analyses, the effects of parameters such as the initial concentration of naphthalene, pH, contact time, and the optimal conditions on naphthalene removal were investigated. Results: XRD patterns and SEM images of the samples confirmed the size of synthesized particles in nanometer. The EDX and DRS spectra analysis showed the presence of two elements (sulfur and nitrogen) and the optical photocatalytic activity in the visible region, respectively. The maximum level of naphthalene removal in the presence of sunlight was obtained to be about 93.55% using a concentration of 0.25 g of thiourea immobilized on glass microbullets at pH=5 and contact time of 90 minutes. Conclusion: The rate of naphthalene removal using the immobilized TiO2 -N-S on glass microbullets was 93.55% in optimal conditions. Therefore, this method has an effective potential for naphthalene removal, and can be used to remove naphthalene from industrial wastewater.

The Impact of Assimilating ZDR Observations on Storm-Scale Ensemble Forecasts of the 31 May 2013 Oklahoma Storm Event

AbstractAssimilation of dual-polarization (dual-pol) observations provides more accurate storm-scale analyses to initialize forecasts of severe convective thunderstorms. This study investigates the impact assimilating experimental sector-scan dual-pol observations has on storm-scale ensemble forecasts and how this impact changes over different data assimilation (DA) windows using the ensemble Kalman filter (EnKF). Ensemble forecasts are initialized after 30, 45, and 60 minutes of DA for two sets of experiments that assimilate either reflectivity and radial velocity only (EXPZ) or reflectivity and radial velocity plus differential reflectivity (EXPZZDR). This study uses the 31 May 2013 Oklahoma event which included multiple storms that produced tornadoes and severe hail, with focus placed on two storms that impacted El Reno and Stillwater during the event.The earliest initialized forecast of EXPZZDR better predicts the evolution of the El Reno storm than EXPZ, but the two sets of experiments become similar at subsequent forecast times. However, the later EXPZZDR forecasts of the Stillwater storm, which organized towards the end of the DA window, produce improved results compared to EXPZ, in which the storm is less intense and weakens. Evaluation of forecast products for supercell mesocyclones (updraft helicity [UH]) and hail show similar results with earlier EXPZZDR forecasts better predicting the UH swaths of the El Reno storm and later forecasts producing improved UH and hail swaths for the Stillwater storm. The results indicate that the assimilation of ZDR over fewer DA cycles can produce improved forecasts when DA windows sufficiently cover storms during their initial development and organization.