Reflectivity Factor Research Articles

Microphysical Characteristics of Raindrop Size Distribution and Implications for Dual-Polarization Radar Quantitative Precipitation Estimations in the Tianshan Mountains, China

In order to improve the understanding of the microphysical characteristics of raindrop size distribution (DSD) under different rainfall rates (R) classes, and broaden the knowledge of the impact of radar wavelengths and R classes on the QPE of dual-polarization radars in the Tianshan Mountains, a typical arid area in China, we investigated the microphysical characteristics of DSD across R classes and dual-polarimetric radar QPE relationships across radar wavelengths and R classes, based on the DSD data from a PARSIVEL2 disdrometer at Zhaosu in the Tianshan Mountains during the summers of 2020 and 2021. As the R class increased, the DSD became wider and flatter. The mean value of the mass-weighted mean diameters (Dm) increased, while the mean value of logarithm normalized intercept parameters (log10 Nw) decreased after increasing from C1 to C3, as the R class increased. The largest contributions to R and the radar reflectivity factor from large raindrops (diameter > 3 mm) accounted for approximately 50% and 97%, respectively, while 84% of the total raindrops were small raindrops (diameter < 1 mm). Dual-polarization radars—horizontal polarization reflectivity (Zh), differential reflectivity (Zdr), and specific differential phase (Kdp)—were retrieved based on the DSD data using the T-matrix scattering method. The DSD-based polarimetric radar QPE relations of a single-parameter (R(Zh), R(Kdp)), and double-parameters (R(Zh,Zdr), R(Kdp,Zdr)) on the S-, C-, and X-bands were derived and evaluated. Overall, the performance of the R(Kdp) (R(Kdp,Zdr)) scheme was better than that of R(Zh) (R(Zh,Zdr)) for the QPE in the three bands. Furthermore, we have for the first time confirmed and quantified the performance differences in the QPE relationship of dual-polarization radars under different schemes, radar wavelengths, and R classes in typical arid areas of China. Therefore, selecting an appropriate dual-polarization radar band and QPE scheme for different R classes is necessary to improve the QPE ability compared with an independent scheme under all R classes.

Calibrating radar wind profiler reflectivity factor using surface disdrometer observations

Abstract. This study uses surface disdrometer reflectivity factor estimates to calibrate the vertical and off-vertical pointing radar beams produced by an ultra high frequency (UHF) band radar wind profiler (RWP) deployed at the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program Southern Great Plains (SGP) Central Facility in northern Oklahoma from April 2011 through July 2019. The methodology consists of five steps. First, the recorded Doppler velocity power spectra are adjusted to account for Nyquist velocity aliasing and coherent integration filtering effects. Second, the spectrum moments are calculated. The third step increases the signal-to-noise ratio (SNR) due to inflated noise power estimates during convective rain events that cause SNR to be biased low. The fourth step determines the RWP calibration constant for one radar beam (called the “reference” beam) by comparing uncalibrated RWP reflectivity factors at 500 m above the ground to 1 min resolution surface disdrometer reflectivity factors. The last step uses the calibrated reference beam reflectivity factor to calibrate the other radar beams during precipitation. There are two key findings. The RWP sensitivity decreased by approximately 3 to 4 dB yr−1 as the hardware aged. This drift was slow enough that the reference calibration constant can be estimated over 3-month intervals using episodic rain events. The calibrated moments are available on the DOE ARM data archive, and the Python processing code is available on public repositories.

Big data analytics capability and contribution to firm performance: the mediating effect of organizational learning on firm performance

PurposeThe study examines how firms may transform big data analytics (BDA) into a sustainable competitive advantage and enhance business performance using BDA. Furthermore, this study identifies various resources and sub-capabilities that contribute to BDA capability.Design/methodology/approachUsing classic grounded theory (GT), resource-based theory and dynamic capability (DC), the authors conducted interviews, which involved an exploratory inductive process. Through a continuous iterative process between the collection, analysis and comparison of data, themes and their relationships appeared. The literature was used as part of the data set in the later phases of data collection and analysis to identify how the study’s findings fit with the extant literature and enrich the emerging concepts and their relationships.FindingsThe data analysis led to developing a conceptual model of BDA capability that described how BDA contributes to firm performance through the mediated impact of organizational learning (OL). The findings indicate that BDA capability is incomplete in the absence of BDA capability dimensions and their sub-dimensions, and expected advancement will not be achieved.Research limitations/implicationsThe research offers insights on how BDA is converted into an enterprise-wide initiative, by extending the BDA capability model and describing the role of per dimension in constructing the capability. In addition, the paper provides managers with insights regarding the ways in which BDA capability continuously contributes to OL, fosters organizational knowledge and organizational abilities to sense, seize and reconfigure data and knowledge to grab digital opportunities in order to sustain competitive advantage.Originality/valueThis article is the first exploratory research using GT to identify how data-driven firms obtain and sustain BDA competitive advantage, beyond prior studies that employed mostly a hypothetico-deductive stance to investigate BDA capability. While the authors discovered various dimensions of BDA capability and identified several factors, some of the prior related studies showed some of the dimensions as formative factors (e.g. Lozada et al., 2019; Mikalef et al., 2019) and some other research depicted the different dimensions of BDA capability as reflective factors (e.g. Wamba and Akter, 2019; Ferraris et al., 2019). Thus, it was found necessary to correctly define different dimensions and their contributions, since formative and reflective models represent various approaches to achieving the capability. In this line, the authors used GT, as an exploratory method, to conceptualize BDA capability and the mechanism that it contributes to firm performance. This research introduces new capability dimensions that were not examined in prior research. The study also discusses how OL mediates the impact of BDA capability on firm performance, which is considered the hidden value of BDA capability.

Generality of leaf spectroscopic models for predicting key foliar functional traits across continents: A comparison between physically- and empirically-based approaches

Leaf spectroscopy provides an efficient way of predicting foliar functional traits, commonly using physically- and empirically-based models. However, the generality of both models has not been fully investigated, and it is not clear if inversion strategies of physically-based models can be transferred across datasets. In this study, we evaluated the generality of leaf spectroscopic models for predicting key foliar functional traits and compared the performance of physically- and empirically-based approaches. Two extensive datasets compiling a total of 3861 foliar samples were collected from 24 field sites in eastern United States and south China. The leaf radiative transfer model PROSPECT was coupled with COSINE (PROCOSINE) to retrieve foliar traits from leaf bidirectional reflectance factor (BRF). A commonly used empirically-based model, partial least squares regression (PLSR) was performed as a comparison. Results showed that both PROSPECT and PROCOSINE can accurately estimate leaf mass per area (LMA) and equivalent water thickness (EWT). Inversion strategies including the selection of optimal spectral domains and the use of prior information (IS3) greatly improved the estimation accuracy of leaf nitrogen, leaf chlorophyll a + b and carotenoids. The estimation accuracies were similar when transferring inversion strategies across datasets, indicating a high level of transferability of physically-based models. PLSR and interval PLSR (iPLSR, via feature selection) could predict foliar traits with high accuracies when cross-validation was performed, and iPLSR achieved higher accuracies. But both the empirical approaches demonstrated low transferability when applied to an independent dataset. Our findings highlight the importance of generalized traits models with respect to development and calibration of leaf radiative transfer model, as well as incorporating representative samples in training empirical models. This study can help us to better understand the variation of foliar traits among and within species, their response to environmental change, as well as plant biodiversity.

Developing resilience: examining the protective factors of early career construction professionals

Work in construction is highly demanding and stressful. Graduates must navigate these imminent challenges as well as the challenges associated with transition as they enter their new learning environment and seek to establish their professional identity. This research examined how resilience can support the transition of early career construction professionals from university into the workforce. Interviews were conducted with twenty-five participants and data was thematically analyzed. Challenges experienced by participants related to structural and cultural conditions of working in construction as well as the transitional career stage. Internal protective factors of emotional objectivity, reflection, goal setting, and physical and mental health emerged as important in positively responding to workplace adversity. Task-related and emotion-related organizational support were considered as important external protective factors that can facilitate the development of internal protective factors. Yet, formal organizational support was often not provided. Findings can inform the design of work and workplace programs which support this new cohort of workers to adapt to an unfamiliar and demanding work environment, as well as provide guidance to university construction management programs on ways to support the development of internal protective factors of emerging professionals. Furthermore, it is expected that students transitioning from university to work, irrespective of discipline, will progress through the three stages of the liminal experience and its possible that access to protective factors supporting resilience may assist students to positively move through this process.

Tree Species Classification in a Complex Brazilian Tropical Forest Using Hyperspectral and LiDAR Data

This study experiments with different combinations of UAV hyperspectral data and LiDAR metrics for classifying eight tree species found in a Brazilian Atlantic Forest remnant, the most degraded Brazilian biome with high fragmentation but with huge structural complexity. The selection of the species was done based on the number of tree samples, which exist in the plot data and in the fact the UAV imagery does not acquire information below the forest canopy. Due to the complexity of the forest, only species that exist in the upper canopy of the remnant were included in the classification. A combination of hyperspectral UAV images and LiDAR point clouds were in the experiment. The hyperspectral images were photogrammetric and radiometric processed to obtain orthomosaics with reflectance factor values. Raw spectra were extracted from the trees, and vegetation indices (VIs) were calculated. Regarding the LiDAR data, both the point cloud—referred to as Peak Returns (PR)—and the full-waveform (FWF) LiDAR were included in this study. The point clouds were processed to normalize the intensities and heights, and different metrics for each data type (PR and FWF) were extracted. Segmentation was preformed semi-automatically using the superpixel algorithm, followed with manual correction to ensure precise tree crown delineation before tree species classification. Thirteen different classification scenarios were tested. The scenarios included spectral features and LiDAR metrics either combined or not. The best result was obtained with all features transformed with principal component analysis with an accuracy of 76%, which did not differ significantly from the scenarios using the raw spectra or VIs with PR or FWF LiDAR metrics. The combination of spectral data with geometric information from LiDAR improved the classification of tree species in a complex tropical forest, and these results can serve to inform management and conservation practices of these forest remnants.

Effectiveness of Sn-addition on optical properties and physicochemical parameters of SnxSb2-xSe3 thin films

This research work is allocated to prepare the novel thin SnxSb2-xSe3 films, TSSe by thermal evaporation procedure at various Sn-content, where 0≤x≤2 at.%. The field-emission scanning electron microscope has been used to investigate the surface nature of these SnxSb2-xSe3 films. X-ray diffraction revealed that all TSSe films disclosed that the films have the polycrystalline nature with the orthorhombic structure without regard to the Sn-content. The optical characteristics of these layers were studied via transmission and reflection spectrophotometric measurements. The Archimedes' principle has been used to measure the density of samples, which was found that its values increase from 5.766 gm/cm3 to 6.136 gm/cm3. Along with, the molar volume decreases from 83.316 cm3/mol to 77.291 cm3/mol. The optical energy gap investigation of thin SnxSb2-xSe3 layers indicated that these layers exposed a direct allowed electronic transition. The optical band-gap energy reduces from 1.191 eV to 1.050 eV, while the band tail width increases from 0.093 eV to 0.155 eV by boosting the Sn-content. Impact of Sn-content on the linear optical parameters also refers to increasing the absorption coefficient, refractive index (from 3.2086 to 3.3317), molar refraction (from 0.756 to 0.771), the interaction strength between the electrons and photons (from 2.439 to 4.065). On the contrary, the steepness parameter, reflection factor, and electronic polarizability decrease as Sn-percentages increase from 0.0 to 2.0 at%. In addition, many other parameters have been discussed, like the optical conductivity, the real and imaginary parts of the dielectric indices, some nonlinear optical parameters, and the semiconductor-type of these films, which detect that they are p-type semiconductors. The investigated parameters and properties showed that these films can be used in many optical applications, like solar cells, photodetectors, batteries, memory devices, and others.

Raindrop size distribution and microphysical features of the extremely severe rainstorm on 20 July 2021 in Zhengzhou, China

By using the observation data of four DSG5-type disdrometers, four automatic weather stations and two dual-polarization Doppler weather radars, this paper analyzes the characteristics of raindrop size distributions (DSDs) and their integral parameters during the severe precipitation in Henan Province, China, specially focusing on the extremely severe rainstorm on the 20 July 2021 in Zhengzhou City. The results show that: (1) In line with most of the severe precipitation in northern China, the July 2021 extreme precipitation were dominated by small raindrops, but medium-sized raindrops with diameter D in 2–4 mm contributed 61.28% to the rain rate R during the time period of extremely severe rainfall at Zhengzhou (ZZ) station, and the raindrops with D > 4 mm contributed 53.74% to the radar reflectivity factor Z. (2) Quantitative evaluation of the gamma model of DSD for different values of R is carried out, and the fitting effect of the gamma model is better for the raindrop spectrum with a single peak structure. However, this method cannot reflect the double-peak structure when R is large. (3) Some differences have been found in the Z-R relationship between Z and R among the four stations (GY, XM, XY, and ZZ). The maximum value of fitting coefficient a appears at the ZZ station, which is close to the a values in the Meiyu season in eastern China. For the other three stations, the a values are comparable to those of typhoons in the western Pacific, but the fitting coefficient b values are less different. (4) The average vertical profiles of dual-polarization radar parameters reveal the microphysical characteristics of the extremely severe rainstorm, that is, there were active ice-phase and warm-rain microphysical processes in the convective system of the extremely severe rainfall, of which the warm-rain process was more dominant.

A Novel Method for Estimating Chlorophyll and Carotenoid Concentrations in Leaves: A Two Hyperspectral Sensor Approach.

Leaf optical properties can be used to identify environmental conditions, the effect of light intensities, plant hormone levels, pigment concentrations, and cellular structures. However, the reflectance factors can affect the accuracy of predictions for chlorophyll and carotenoid concentrations. In this study, we tested the hypothesis that technology using two hyperspectral sensors for both reflectance and absorbance data would result in more accurate predictions of absorbance spectra. Our findings indicated that the green/yellow regions (500-600 nm) had a greater impact on photosynthetic pigment predictions, while the blue (440-485 nm) and red (626-700 nm) regions had a minor impact. Strong correlations were found between absorbance (R2 = 0.87 and 0.91) and reflectance (R2 = 0.80 and 0.78) for chlorophyll and carotenoids, respectively. Carotenoids showed particularly high and significant correlation coefficients using the partial least squares regression (PLSR) method (R2C = 0.91, R2cv = 0.85, and R2P = 0.90) when associated with hyperspectral absorbance data. Our hypothesis was supported, and these results demonstrate the effectiveness of using two hyperspectral sensors for optical leaf profile analysis and predicting the concentration of photosynthetic pigments using multivariate statistical methods. This method for two sensors is more efficient and shows better results compared to traditional single sensor techniques for measuring chloroplast changes and pigment phenotyping in plants.

Islamic corporate sustainability practices index aligned with SDGs towards better financial performance: Evidence from the Malaysian and Indonesian Islamic banking industry

Exploring the link of corporate sustainability practices towards financial performance remains an area of interest to many scholars. But still, the Islamic perspective of the nexus is over sighted. In this vein, the main objective of this study is to inquire about the nexus of corporate sustainability practices towards financial performance from an Islamic perspective. However, the major challenge in this regard is the unavailability of an Islamic corporate sustainability index. To cope with the challenge, this study developed a novel Islamic corporate sustainability practices index and aligned it with sustainable development goals for greater generalizability and better financial performance. The study collected 10 years of panel data (2009–2018) for 16 Islamic banks in Malaysia and 12 Islamic banks in Indonesia. Panel corrected standard errors regression technique was used to analyse panel data. Results were first generated on the combined dataset including both Malaysia and Indonesia, and then from individual countries' perspectives to obtain a holistic point of view. Furthermore, results are also generated on Islamic corporate sustainability practices as a formative factor as well as a reflective factor indicating (environmental, economic and social) dimensions. Results of panel corrected standard errors regression analysis show that Islamic corporate suitability practices as a formative factor have a significant positive impact on financial performance from the combined as well as the separate dataset from Malaysia and Indonesia. However, results of the reflective factors of Islamic corporate sustainability practices show variation in the combined (Malaysian and Indonesian) dataset. These results provide insights into various policy formulations at Malaysian and Indonesian Islamic banks in specific. And in general, these results insights into the world Islamic banking industry for ensuring better compliance with sustainable development goals aimed at achieving greater financial performance. More importantly, this study may serve as a launching pad for the development of the global Islamic banking corporate sustainability practices index.

Improving the standard protocol for above-water reflectance measurements: 1. Estimating effective wind speed from angular variation of sunglint.

The standard above-water protocol for measurement of water reflectance uses a measurement of wind speed to estimate the air-water interface reflectance factor and, thus, remove reflected skylight from upwelling radiance. This aerodynamic wind speed measurement may be a poor proxy for the local wave slope distribution in cases such as fetch-limited coastal and inland waters and/or where there are spatial or temporal differences between the wind speed measurement and the location of reflectance measurements. Here, an improved method is proposed, with a focus on sensors mounted on autonomous pan-tilt units and deployed on fixed platforms, replacing the aerodynamic wind speed measurement by optical measurements of angular variation of upwelling radiance. Using radiative transfer simulations, it is shown that the difference between two upwelling (i.e.,water plus air-water interface) reflectances acquired at least 10° apart from each other in the solar principal plane is strongly and monotonically related to effective wind speed. The approach shows good performance in twin experiments using radiative transfer simulations. Limitations of the approach are identified, including difficulties for a very high Sun zenith angle (>60∘), very low wind speed (<2m s -1), and, potentially, cases in which nadir-pointing angles are limited by optical perturbations from the viewing platform.

Estimating leaf nitrogen and chlorophyll content in wheat by correcting canopy structure effect through multi-angular remote sensing

Canopy scattering coefficient (CSC) is the ratio of bidirectional reflectance factor (BRF) to directional area scattering coefficient (DASF), and has been successfully applied to correct the effect of canopy structure. The key to calculate CSC is to calculate DASF, which is determined by the intercept b and slope k of the linear relationship between BRF and BRFλΩωλ (the ratio of hyperspectral BRF in certain view direction to leaf albedo (ωλ). However, due to the limitation of multispectral bands, how to accurately calculate crop DASF during the whole growth period using multispectral UAV data is still an urgent problem to be solved. In this study, wheat canopy multi-angular (0°, −30°, −45°) datasets including near-ground hyperspectral data, UAV multispectral data, and PROSAIL simulation data were obtained for three consecutive years. The DASFk-b model was proposed to estimate b and k based on multispectral sensors by relative accumulated growing degree days (RAGDD) and BRF. The previously developed DASFg-NIR model and vegetation index (VI) model were compared with DASFk-b model under different view angles (VZAs), to evaluate their performances in correcting canopy structural effect, estimating leaf nitrogen content (LNC) and leaf chlorophyll content (LCC) based on generalized additive model (GAM). The results showed that the hyperspectral band range suitable for estimating wheat DASF was 710–760 nm. Parameter b decreased with increased N application rates, and activated first and then inhibited with increased RAGDD; the tendency of k, DASFHy were opposite. Compared with CSCg-NIR (calculated from DASFg-NIR model) and VIs, CSCk-b (calculated from DASFk-b model) had the best correction effect on canopy structure under different VZAs. The estimation accuracy of LNC and LCC using CSCk-b was improved compared with CSCg-NIR and VIs, with RRMSE values of 9.2% and 7.0%, respectively, and the recommended VZA was −45° for both models.

Refreezing of Partially Melted Hydrometeors: Polarimetric Radar Observations and Microphysical Model Simulations

Abstract The discovery of a polarimetric radar signature indicative of hydrometeor refreezing has shown promise in its utility to identify periods of ice pellet production. Uniquely characterized well below the melting layer by locally enhanced values of differential reflectivity (ZDR) within a layer of decreasing radar reflectivity factor at horizontal polarization (ZH), the signature has been documented in cases where hydrometeors were completely melted prior to refreezing. However, polarimetric radar features associated with the refreezing of partially melted hydrometeors have not been examined as rigorously in either an observational or microphysical modeling framework. Here, polarimetric radar data—including vertically pointing Doppler spectral data from the Ka-band Scanning Polarimetric Radar (KASPR)—are analyzed for an ice pellets and rain mixture event where the ice pellets formed via the refreezing of partially melted hydrometeors. Observations show that no such distinct localized ZDR enhancement is present, and that values instead decrease directly beneath enhanced values associated with melting. A simplified, explicit bin microphysical model is then developed to simulate the refreezing of partially melted hydrometeors, and coupled to a polarimetric radar forward operator to examine the impacts of such refreezing on simulated radar variables. Simulated vertical profiles of polarimetric radar variables and Doppler spectra have similar features to observations, and confirm that a ZDR enhancement is not produced. This suggests the possibility of two distinct polarimetric features of hydrometeor refreezing: ones associated with refreezing of completely melted hydrometeors, and those associated with refreezing of partially melted hydrometeors. Significance Statement There exist two pathways for the formation of ice pellets: refreezing of fully melted hydrometeors, and refreezing of partially melted hydrometeors. A polarimetric radar signature indicative of fully melted hydrometeor refreezing has been extensively documented in the past, yet no study has documented the refreezing of partially melted hydrometeors. Here, observations and idealized modeling simulations are presented to show different polarimetric radar features associated with partially melted hydrometeor refreezing. The distinction in polarimetric features may be beneficial to identifying layers of supercooled liquid drops within transitional winter storms.

Surface Crack Monitoring by Rayleigh Waves with a Piezoelectric-Polymer-Film Ultrasonic Transducer Array.

This paper presents a method for measuring surface cracks based on the analysis of Rayleigh waves in the frequency domain. The Rayleigh waves were detected by a Rayleigh wave receiver array made of a piezoelectric polyvinylidene fluoride (PVDF) film and enhanced by a delay-and-sum algorithm. This method employs the determined reflection factors of Rayleigh waves scattered at a surface fatigue crack to calculate the crack depth. In the frequency domain, the inverse scattering problem is solved by comparing the reflection factor of the Rayleigh waves between the measured and the theoretical curves. The experimental measurement results quantitatively matched the simulated surface crack depths. The advantages of using the low-profile Rayleigh wave receiver array made of a PVDF film for detecting the incident and reflected Rayleigh waves were analyzed in contrast with those of a Rayleigh wave receiver using a laser vibrometer and a conventional lead zirconate titanate (PZT) array. It was found that the Rayleigh waves propagating across the Rayleigh wave receiver array made of the PVDF film had a lower attenuation rate of 0.15 dB/mm compared to that of 0.30 dB/mm of the PZT array. Multiple Rayleigh wave receiver arrays made of the PVDF film were applied for monitoring surface fatigue crack initiation and propagation at welded joints under cyclic mechanical loading. Cracks with a depth range of 0.36-0.94 mm were successfully monitored.

Path Diagram of entrepreneurship in the COVID-19 era

- The process that goes from prospective decisions (oriented to risks of maximum profits with respect to minimum insurance benefits) to deliberate actions (oriented by avoidance of failures, based on the systematization of errors and successes) is addressed in the present work, aiming to specify a model for the study of Internet entrepreneurship. A non-experimental study was carried out with a non-probabilistic selection of 100 entrepreneurs. From a structural model, the reflective factor of the construct was found to be deliberate actions, but such findings are only applicable to the sample since the type of study, sampling, and statistical analysis suggest the contrast of the model in other scenarios would increase the percentage of the explained variance of its factors, that added to 57% in this case.

Reflective Practice and Factors Affecting it: Perceptions of Pediatric Surgery Residents

Background: There is scarcity of literature about factors affecting reflective practices in local context. By focusing on these factors, we can help promote engagement in reflective practices in our culture. Objective of this study was to explore the barriers to and facilitators of reflective practice by post graduate surgical residents. Methods: Using action research study design, qualitative research was conducted in the department of Pediatric Surgery, Mayo Hospital to explore different factors affecting reflective practice in postgraduate surgical residents in their daily practice. A workshop on reflective practices was conducted, followed by weekly morbidity/mortality meetings and case-based discussions deliberating using Gibbs' reflective cycle. After a year, focus group discussion using a heterogenous group of nine residents was conducted to explore the factors affecting reflective practice. It was transcribed and analyzed thematically. Results: Reflective practice was perceived to improve critical appraisal, deeper learning, self-monitoring, and patients' outcomes. There was resistance towards reflective writing. Themes related to factors affecting reflective practice were organization, time allocation, communication, workplace environment, interpersonal relations, guided reflection, and feedback. Involvement of multiple disciplines in 'reflection before action' was identified for future implementation. Conclusion: Provision of guided reflection and constructive feedback were the main facilitators of reflective practice. Generally, improving organization, workplace environment, interpersonal relations, and accommodating individual learning styles can enhance reflective practice in our context, and help developing habit of lifelong learning.

Multiscale Analysis of Reflected Radiation on Lunar Surface Region Based on MRRT Model

The moon has stable luminosity. Radiometric calibration on the lunar region is a good step in the right direction with the expansion of instrument observation capabilities. The uneven composition and terrain types of the lunar surface make it possible for inaccuracies in albedo calculation from coarse-scale data if the within-pixel topology is overlooked. The expression between the region’s bidirectional reflectance factor (BRF) and the actual microtopography reflectance was established by the multiple reflections of radiation between terrains (MRRT) model. This research studied the radiation properties on the lunar surface region at various spatial resolutions (scales) based on the MRRT model. To determine the ideal scale of microtopography to be built, the scale-effect evaluation factor of albedo is established, and the scale-effect function is fitted. Experiments demonstrate that a microtopography with a spatial resolution of 60 m to 120 m, with 80 m being the most suitable scale, can be constructed for an area having (6000 × 6000) m2. This research adds to the MRRT model’s applicability analysis in multiscale DEM modeling, helps choose and build a radiation calibration field on the lunar surface, and lays the groundwork for employing the area of the lunar surface for radiation calibration.

Relationships between lightning occurrence and summer precipitation characteristics over china observed by GPM core observatory

The relationships between lightning occurrence and precipitation properties observed from the Dual-frequency Precipitation Radar and the Microwave Imager onboard the core observatory of the Global Precipitation Measurement Mission over China are investigated. The results indicate that lightning precipitation features (LPFs) typically account for <11% of the total precipitation features (PFs) over China, with the convective rain types accounting for ∼40%. The LPFs are more organized with wider spanning areas over Eastern China than Western China, and embedded with wider areas of convective cores than the non-lightning PFs. The probability of lightning (POL) increases linearly with the near-surface rain rate, liquid water path (LWP), and non-liquid water path (NLWP), while increases exponentially with the equivalent reflectivity factor (Ze). The precipitation profiles reveal that the maximum Ze values at higher altitudes are more sensitive to lightning occurrence than the ones at lower altitudes. The POL reaching above 80% mainly occurs when the areas of Ze above 20 dBZ or 30 dBZ exceed specific thresholds above the melting layer, while also occurs below the melting layer for the areas of Ze above 40 dBZ. The established precipitation parameter threshold-based lightning delineation scheme reveals that the maximum or minimum precipitation properties within PFs perform better than the mean ones in discriminating lightning. Furthermore, there is a great regional variance in the optimum thresholds of lightning delineation by precipitation properties over four typical regions of China. Overall, the present study may be helpful in the future prediction and nowcasting of lightning storms in numerical models.

The effects of surface roughness on the calculated, spectral, conical–conical reflectance factor as an alternative to the bidirectional reflectance distribution function of bare sea ice

Abstract. The conical–conical reflectance factor (CCRF) has been calculated as an alternative to the bidirectional reflectance distribution function (BRDF) for three types of bare sea ice with varying surface roughness (σ= 0.1–10) and ice thicknesses (50–2000 cm) over an incident solar irradiance wavelength range of 300–1400 nm. The comprehensive study of the CCRF of sea ice presented here is paramount for interpreting sea ice measurements from satellite imagery and inter-calibrating space-borne sensors that derive albedo from multiple multi-angular measurements. The calculations performed by a radiative-transfer code (PlanarRad) show that the CCRF of sea ice is sensitive to realistic values of surface roughness. The results presented here show that surface roughness cannot be considered independently of sea ice thickness, solar zenith angle and wavelength. A typical CCRF of sea ice has a quasi-isotropic reflectance over the hemisphere, associated with a strong forward-scattering peak of photons. Surface roughness is crucial for the location, size and intensity of the forward-scattering peak. As the surface roughness increases, a spreading of the CCRF peak is observed. The hemisphere was split in to 216 quadrangular regions or quads. The peak remains specular for the smaller surface roughnesses (σ=0.001 to σ=0.01), whereas for larger surface roughness features (above σ=0.05), the peak spreads out over multiple quads with a lower intensity than for smaller roughness features, and the highest value is displaced further out on the solar principal plane. Different types of sea ice have a similar pattern with wavelength: the CCRF increases by 30 % from first-year sea ice to multi-year sea ice at 400 nm and up to 631 % at 1100 nm, 32 % from melting sea ice to multi-year sea ice at 400 nm and a maximum of 98 % at 900 nm, and 11 % from melting sea ice to first-year sea ice at 400 nm and up to 86 % at 800 nm. The CCRF calculations presented in this study form the first set of complete CCRF values as an approximation of the BRDF for bare sea ice with a wide range of configurations.

In Situ Experimental Study of Cloud-Precipitation Interference by Low-Frequency Acoustic Waves

Since acoustic agglomeration is an effective pre-treatment technique for removing fine particles, it can be considered as a potential technology for applications in aerosol pollution control, industrial dust and mist removal, and cloud and precipitation interference. In this study, the cloud-precipitation interference effect was evaluated in situ based on a multi-dimensional multi-scale monitoring system. The variations in the spatial and temporal distribution of rainfall near the surface and the characteristics of precipitation droplets in the air were investigated. The results indicate that strong low-frequency acoustic waves had a significant impact on the macro-characteristics of rainfall clouds, the microphysical structure of rain droplets and near-surface precipitation, and various microwave parameters. In terms of physical structure, the precipitation cloud’s base height decreased significantly upon opening the acoustic device, while agglomeration and de-agglomeration of raindrops were in a dynamic equilibrium. When the sound generator was on, the particle concentration at a sampling attitude of 500−1700 m and the proportion of particles with diameters of 1–1.5 mm decreased significantly (by 1–5 ln [1/m3·mm]). In contrast, the particle concentration increased by 1–3 ln [1/m3·mm] at a sampling attitude below 400 m. Moreover, during acoustic interference, the reflectivity factor surged by 2.71 dBZ within 1200 m of the operation centre. Overall, the spatial and temporal distributions of rainfall rates and cumulative precipitation within 5 km of acoustic operation were uneven and influenced by local terrain and background winds.