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Phytoremediation technology based on living green plants would clean up water pollution. Through hydroponic experiment, the effects of different concentration of 2, 4-dinitrophenol (2, 4-DNP) on the photosynthetic and chlorophyll fluorescence parameters of Salix babylonica, and the absorption and purification effect of S. babylonica on 2, 4-DNP were measured to explore the tolerance of S. babylonica to 2, 4-DNP and the feasibility to purify dinitrophenol waste water by it. The biomass, actual photochemical efficiency (PSII), net photosynthetic rate (Pn), photochemical quenching coefficient (qP), stomatal conductance (Gs), transpiration rate (Tr), maximum photochemical efficiency (Fv/Fm) and chlorophyll content of the S. babylonica showed downward trend with the increasing exposure concentrations of 2,4-DNP, but the intercellular CO2 concentration (Ci) appeared upward trend. Non-photochemical quenching coefficient (NPQ) increased at 5 mg L–1, then declined with the increase concentrations of 2, 4-DNP. In addition, the percent removal of 2, 4-DNP in 20 mg L–1 waste water was 91.4%. In conclusion, 2, 4-DNP significantly inhibits Pn of S. babylonica and the reduction of Pn was caused by decreasing Gs, carboxylation efficiency and chlorophyll content. When the concentration of 2, 4-DNP is not more than 20 mg L–1, S. babylonica can remove 2, 4-DNP efficiently. [ABSTRACT FROM AUTHOR]

While the forests on Mount Taishan are predominantly man-made, there is a notable vertical variation in vegetation. This study employs the method of cloud model, quantifying uncertainty (fuzziness and randomness) of things. Utilizing digital elevation model (DEM) and vegetation distribution data, we constructed elevation cloud models for Mount Taishan’s deciduous broad-leaved, temperate coniferous, and mixed coniferous-broadleaved forests. Using three numerical features of the cloud model—Expectation (EX), Entropy (EN), and Hyper-entropy (HE)—we quantitatively analyzed the macro regularity and local heterogeneity of Mount Taishan’s forests vertical distribution from the perspective of uncertainty theory. The results indicate: (1) The EX of the core zone elevation of deciduous broad-leaved forest is 716.65 m, temperate coniferous forest is 1053.51 m, and mixed coniferous-broadleaved forest is 1384.09 m. The variation range of the core zone distribution height is smaller in the mixed coniferous-broadleaved forest (EN: 53.74 m) compared to deciduous broad-leaved forest (EN: 99.63 m) and temperate coniferous forest (EN: 121.70 m). (2) The fuzziness and randomness of the distribution height of the lower extension zones of deciduous broad-leaved forest and temperate coniferous forest (EN: 75.15 m, 184.56 m; HE: 24.09 m, 63.54 m) are greater than those of the upper extension zones (EN: 44.75 m, 42.49 m; HE: 14.48 m, 13.23 m). (3) The distribution fuzziness and randomness within temperate coniferous forests exceed those of deciduous broad-leaved forests. Within the core zones, the uncertainty regarding the vertical distribution of vegetation across different aspects remains consistent, which retains the characteristic of man-made forests. However, in transition areas, there is significant disparity, reflecting the adaptive relationship between vegetation and its environment to some extent. In the upper and lower extension zones of deciduous broad-leaved forests, the EX values for the vertical distribution height of mixed coniferous and broad-leaved forests differ significantly from those of deciduous broad-leaved forests (the difference is 22.82–39.15 m), yet closely resemble those of temperate coniferous forests (the difference is 4.79–7.94 m). This suggests a trend wherein deciduous broad-leaved tree species exhibit a proclivity to encroach upon coniferous forest habitats. The elevation cloud model of vertical vegetation zones provides a novel perspective and method for the detailed analysis of Mount Taishan’s vegetation vertical differentiation. [ABSTRACT FROM AUTHOR]

A diode laser sensor based on absorption spectroscopy has been developed for sensitive measurement of CO 2 concentration at high-temperature. Measurement of CO 2 can provide information about the extent of combustion and mix in a combustor that may be used to improve fuel efficiency. Most methods of in-situ combustion measurement of CO 2 use the spectroscopic parameters taken from database like HITEMP which is mainly derived from the theoretical calculation and remains a high degree of uncertainty in the spectroscopic parameters. A fiber-coupled diode laser system for measurement of CO 2 in combustion environment by use of the high-temperature spectroscopic parameters which are obtained by experiment was proposed. Survey spectra of the R (50) line of CO 2 at 5007.787 cm −1 were recorded at high-temperature and various pressures to determine line intensities. The line intensities form the theoretical foundation for future applications of this diode laser sensor system. Survey spectra of four test gas mixtures containing 5.01%CO 2 , 10.01%CO 2 , 20.08%CO 2 , and 49.82%CO 2 were measured to verify the accuracy of the diode laser sensor system. The measured results indicate that this sensor can measure CO 2 concentration with 2% uncertainty in high temperatures. [ABSTRACT FROM AUTHOR]

Tocopherol cyclase (VTE1) plays a key role in promoting the production of γ-tocopherol and improving total tocopherol content in photosynthetic organisms. Walnut is an important source of tocopherols in the human diet, and γ-tocopherol is the major tocopherol compound in walnut kernels. In this study, a full-length cDNA of the VTE1 gene was isolated from walnut using RT-PCR and RACE, and designated as JrVTE1. The full-length cDNA of the JrVTE1 gene contained a 1353-bp open-reading frame encoding a 451-amino-acid protein with a calculated molecular weight of 49.5 kDa. The deduced JrVTE1 protein had a considerable homology with other plant VTE1s and belonged to the tocopherol cyclase family. Functional characterization of JrVTE1 by heterologous expression was carried out in E. coli BL21 (DE3) and microshoot lines of the fruit trees jujube (Zizyphus jujuba var. spinosa) and pear (Pyrus communis) cultivar ‘Old Home’. JrVTE1 in E. coli expressed as a 50 kDa protein, as expected. One or two copies of the transferred JrVTE1 gene were detected in the genomes of representative transgenic lines (from the initial transgenic plants) of jujube and pear by gel blots analysis. Over-expression of JrVTE1 in jujube and pear resulted in an accumulation of tocopherol and a shift in tocopherol composition in leaf, root and stem tissues. In the transgenic jujube, the total tocopherol content increased by 29.8 μg/g in the stems of line J3, 43.7 and 22.5 μg/g in the roots and leaves of line J1, respectively, whereas in the transgenic pear it increased by 47.3 μg/g in the leaf of line P3, and 16.7 and 10.4 μg/g in roots and stems of line P9, respectively. In the examined tissues of transgenic plants, the highest accumulation rate was the γ-tocopherol. These results indicate that JrVTE1 is one of the rate-limiting enzymes for tocopherol production and could be used to improve the tocopherol content of tree crops through genetic engineering. [ABSTRACT FROM AUTHOR]

Fusarium solani exerts detrimental effects on plant growth, which is one of the reasons for the incidence of apple replant disease. Arbuscular mycorrhizal fungi (AMF) enhance plant resistance to Fusarium wilt; however, the mechanism remains poorly understood. Therefore, the present study investigated the symbiosis between apple and AMF and explored the physiology, especially nitrate metabolism, antioxidant defense, and photosynthetic performance, when infected by F. solani. The experiment was carried out with four treatments, namely −AMF − F. solani, −AMF + F. solani, −AMF + F. solani, and + AMF + F. solani. In this study, the −AMF + F. solani treatment increased the activity of enzymes associated with nitrogen metabolism, such as the nitrate and nitrite reductases, in the apple root system. The +AMF + F. solani treatment showed higher antioxidant enzyme activities than the −AMF + F. solani by F. solani infection. The apple seedlings of the +AMF + F. solani treatment decreased reactive oxygen accumulation and reduced the oxidative damages triggered by F. solani infection. The improvement in antioxidant capacity due to the +AMF + F. solani treatment was closely associated with the upregulation of genes related to the antioxidant system. The F. solani infection greatly damaged the photosynthetic process, while the +AMF + F. solani treatment significantly improved it compared to the −AMF + F. solani treatment. In conclusion, the study demonstrated that the apple‐AMF symbiosis plays an active role in regulating the resistance against F. solani infection by enhancing defense response and nitrogen metabolism. [ABSTRACT FROM AUTHOR]

Land-cover information is significant for land-use planning, urban management, and environment monitoring. This paper presented a novel extended topology-preserving segmentation (ETPS)-based multi-scale and multi-feature method using the convolutional neural network (EMMCNN) for high spatial resolution (HSR) image land-cover classification. The EMMCNN first segmented the images into superpixels using the ETPS algorithm with false-color composition and enhancement and built parallel convolutional neural networks (CNNs) with dense connections for superpixel multi-scale deep feature learning. Then, the multi-resolution segmentation (MRS) object hand-delineated features were extracted and mapped to superpixels for complementary multi-segmentation and multi-type representation. Finally, a hybrid network was designed to consist of 1-dimension CNN and multi-layer perception (MLP) with channel-wise stacking and attention-based weighting for adaptive feature fusion and comprehensive classification. Experimental results on four real HSR GaoFen-2 datasets demonstrated the superiority of the proposed EMMCNN over several well-known classification methods in terms of accuracy and consistency, with overall accuracy averagely improved by 1.74% to 19.35% for testing images and 1.06% to 8.78% for validating images. It was found that the solution combining an appropriate number of larger scales and multi-type features is recommended for better performance. Efficient superpixel segmentation, networks with strong learning ability, optimized multi-scale and multi-feature solution, and adaptive attention-based feature fusion were key points for improving HSR image land-cover classification in this study. [ABSTRACT FROM AUTHOR]

The Moon is a stable light source for the radiometric calibration of satellite sensors. It acts as a diffuse panel that reflects sunlight in all directions, however, the lunar surface is heterogeneous due to its topography and different mineral content and chemical composition at different locations, resulting in different optical properties. In order to perform radiometric calibration using the Moon, a lunar irradiance model using different observation geometry is required. Currently, two lunar irradiance models exist, namely, the Robotic Lunar Observatory (ROLO) and the Miller and Turner 2009 (MT2009). The ROLO lunar irradiance model is widely used as the radiometric standard for on-orbit sensors. The MT2009 lunar irradiance model is popular for remote sensing at night, however, the original version of the MT2009 lunar irradiance model takes less consideration of the heterogeneous lunar surface and lunar topography. Since the heterogeneity embedded in the lunar surface is the key to the improvement of the lunar irradiance model, this study analyzes the influence of the heterogeneous surface on the irradiance of moonlight based on model data at different scales. A heterogeneous correction factor is defined to describe the impact of the heterogeneous lunar surface on lunar irradiance. On the basis of the analysis, the following conclusions can be made. First, the influence of heterogeneity in the waning hemisphere is greater than that in waxing hemisphere under all 32 wavelengths of the ROLO filters. Second, the influence of heterogeneity embedded in the lunar surface exerts less impact on lunar irradiance at lower resolution. Third, the heterogeneous correction factor is scale independent. Finally, the lunar irradiance uncertainty introduced by topography is very small and decreases as the resolution of model data decreases due to the loss of topographic information. [ABSTRACT FROM AUTHOR]

Forest soils are important components of forest ecosystems, and soil quality assessment as a decision-making tool to understand forest soil quality and maintain soil productivity is essential. Various methods of soil quality assessment have been developed, which have occasionally generated inconsistent assessment results between soil types. We assessed the soil quality of five communities (herb, shrub, Quercus acutissima, Pinus thunbergii, and Q. acutissima–P. thunbergii mixed plantation) using two common methods of dry and barren mountains in the Yimeng Mountain area, China. Sixteen soil physical, chemical and biological properties were analysed. The soil quality index was determined using the established minimum data set based on the selection results of principal component analysis and Pearson analysis. Silt, soil total phosphorus (P), soil total nitrogen (N), L-leucine aminopeptidase, acid phosphatase and vector length were identified as the most representative indicators for the minimum data set. Linear regression analysis showed that the minimum data set can adequately represent the total data set to quantify the impact of different communities on soil quality (P < 0.001). The results of linear and non-linear methods of soil quality assessment showed that the higher soil quality index was Pinus forest (0.59 and 0.54), and the soil quality index of mixed plantation (0.41 and 0.45) was lower, which was similar to the herb community (0.37 and 0.44). Soil quality was mostly affected by soil chemical properties and extracellular enzyme activities of different communities, and the different reasons for the low soil quality of mixed plantations were affected by soil organic carbon (C) and total C. Overall, we demonstrate that the soil quality index based on the minimum data set method could be a useful tool to indicate the soil quality of forest systems. Mixed plantations can improve soil quality by increasing soil C, which is crucial in ecosystem balance. [ABSTRACT FROM AUTHOR]

The irrational land use patterns in the Yellow River Delta (YRD) have resulted in an imbalance in ecological stoichiometry, leading to secondary salinization and soil degradation. However, there is limited knowledge about the long-term response of soil and enzyme stoichiometry to land use. This hampers our ability to optimize land use in the YRD to alleviate nutrient limitation and thus promote ecological stoichiometric balance. We investigated the stoichiometry of soil and enzyme carbon (C), nitrogen (N), and phosphorus (P) in three land use patterns (Alfalfa artificial grassland, AG; wheat–maize rotation field, WM; native grassland, PC) established for 19 years in the YRD. The results showed that the soil stoichiometry of the three land uses in the YRD was lower than the world and Chinese averages, indicating lower C and N levels. Nutrient limitations of soil microorganisms were C and P due to an enzyme C:N ratio greater than 1:1 and vector angle greater than 45°. The three land use patterns have different advantages in alleviating nutrient limitations in the YRD. AG promotes soil macroaggregate formation, reduces soil salt content, improves nutrient availability, and mitigates N limitation. This makes AG more conducive to improving the poor soil structure, high soil salinity, and stoichiometric imbalance in the YRD to mitigate local soil degradation and be suitable for long-term continuous cultivation. WM is beneficial for increasing soil total C content due to straw return. However, WM does not reduce soil salinity. WM is more suitable for intercropping or crop rotation to improve soil C content in the YRD. Although PC can alleviate soil microbial C limitation due to its significantly lower vector length than AG and WM, the low nutrient levels hindered its ability to alleviate local soil nutrient limitation. In conclusion, our study provides a theoretical basis for rational land use in the YRD to mitigate soil degradation. [ABSTRACT FROM AUTHOR]

Carbon catabolite repression (CCR) is a very important mechanism for efficient use of carbon sources in the environment and is necessary for the regulation of fungal growth, development, and pathogenesis. Although there have been extensive studies conducted regarding this mechanism in fungi, little is yet known about the effects of CreA genes on Valsa mali. However, based on the results obtained in this study for the identification of the VmCreA gene in V. mali, it was determined that the gene was expressed at all stages of fungal growth, with self-repression observed at the transcriptional level. Furthermore, the functional analysis results of the gene deletion mutants (ΔVmCreA) and complements (CTΔVmCreA) showed that the VmCreA gene played an important role in the growth, development, pathogenicity, and carbon source utilization of V. mali. [ABSTRACT FROM AUTHOR]

A number of strict lockdown measures were implemented in the areas most affected by COVID-19 in China, including Ji'nan city, from 24 January to 7 February 2020. Due to these forced restrictions, the pollution levels in cities across the country drastically decreased within just a few days. Since traffic pollution and industrial emissions are important factors affecting regional air quality, congestion has a significant impact on the environment. Therefore, using the aid of air quality data for six pollutants (PM10, PM2.5, SO2, NO2, CO and O3) from 11 monitoring stations (located in urban, suburban and urban-industrial regions) across Ji'nan, we employed the air quality index (AQI) to investigate the spatial pattern of air quality in the pre-COVID-19 (pre-COVID) and COVID-19-related lockdown (COVID lockdown) periods. The results showed that air quality significantly improved during the COVID lockdown period. Among the selected pollutants, compared to the corresponding pre-COVID levels, the greatest reduction was observed for the concentration of NO2 (54.02%), while the smallest reduction was observed for the concentration of SO2 (27.92%). The PM2.5 (38.73%), PM10 (44.92%) and CO (30.60%) levels also decreased during the COVID lockdown period; only the O3 concentration increased (37.42%) during this period. Overall, air quality improved by approximate improvements of 37.33% during the COVID lockdown period. Approximately 35.48%, 37.01% and 43.43% in the AQI were observed in urban, suburban and urban-industrial regions, respectively. Therefore, the AQI exhibited remarkable regional differences in Ji'nan. This study demonstrates the contributions of the transportation sector and local emissions to improving air quality in typical urban areas, and these research results can provide guidance for the further monitoring of air pollution in northern Chinese cities. [ABSTRACT FROM AUTHOR]

The aim of this study is to evaluate the aerosol influence on LST retrieval with two algorithms (split-window (SW) method and a four-channel based method) using simulated data under typical conditions. The results show that the root mean square error (RMSE) decreases to approximately 2.3 K for SW method and 1.5 K for four channel based method when VZA = 60° and visibility = 3 km; an RMSE would be increased by approximately 1.0 K when visibility varies from 3 km to 23 km. Moreover, a detailed sensitivity analysis under a visibility of 3 km and 23 km is performed in terms of uncertainties of land surface emissivity (LSE), water vapor content (WVC), and instrument noise, respectively. It is noted that the four-channel based method is more sensitive to LSE than SW method, especially for dry atmosphere; LST error caused by a WVC uncertainty of 20% is within 1.5 K for SW method and within 0.8 K for four-channel based method; the instrument noise would introduce LST error with a maximum standard deviation of 0.5 K and 0.04 K for the four-channel based method and SW method, respectively. [ABSTRACT FROM AUTHOR]

Robust calibration and validation (Cal and Val) should guarantee the accuracy of the retrieved information, make the remote sensing data consistent and traceable, and maintain the sensor performance during the operational phase. The DRAGON program has set up many remote sensing research topics on various application domains. In order to promote the effectiveness of data modeling and interpretation, it is necessary to solve various challenges in Cal and Val for quantitative RS applications. This project in the DRAGON 4 program aims to promote the cooperation of the Cal and Val experts from European and Chinese institutes in Cal and Val activities, and several achievements have been obtained in the advanced on-orbit optical sensor calibration, as well as microwave remote sensor calibration and product generation. The outcomes of the project have benefited the related remote sensing modeling and product retrieval, and promoted the radiometric calibration network (RadCalNet) as an international operational network for calibration, intercalibration, and validation. Moreover, this project provided local governments with a more accurate OMI NO2 data in China, which were used to study the air quality control during APEC period, Parade period and G20 period. This will be of ongoing be value for monitoring atmospheric environmental quality and formulating pollution control strategies. [ABSTRACT FROM AUTHOR]

The occurrence of apple replant disease (ARD) is inevitable during the renewal and transformation of aging orchards. This disease seriously threatens the healthy and sustainable development of the apple industry. Arbuscular mycorrhizal fungi (AMF) have shown great potential in promoting plant growth, resisting soil-pathogen infection and improving soil quality. However, there is relatively little information available about the application of AMF in the prevention and control of ARD. In this study, we conducted a pot and field experiment were conducted with inoculation of AMF (Paraglomus sp. SW1) on apple rootstock (Malus hupehensis Rehd. in the pot experiment and M9T337 in the field experiment) to explore the biocontrol effect of AMF on ARD by comparing the changes in fungal and AMF communities after AMF inoculation on apples under replanting conditions. AMF-inoculated apple was used as the treatment, while non-inoculated apple was used as the control. The results showed that AMF-inoculated plants not only promoted the growth of M. hupehensis Rehd., but also stimulated the branch elongation growth of young apple trees, compared to the control. After inoculation with AMF, the community structure of soil fungi and arbuscular mycorrhizal fungi changed significantly, with an increase in the abundance of fungi and AMF in soil, and a significant reduction in the abundance of Fusarium spp., especially Fusarium moniliforme , Fusarium solani , and Fusarium proliferatum. Additionally, the soil enzyme activity increased significantly. Furthermore, the levels of ammonium nitrogen (NH 4 +), nitrate nitrogen (NO 3 −), available phosphorus (AP), available potassium (AK), organic matter (SOM), and pH in the rhizosphere soil were significantly related to the changes in the community structure of fungi and AMF. The AP, NH 4 + and NO 3 − was found to drive the fungal communities, while NH 4 + and NO 3 − drove the AM fungal communities in replanting soil. In conclusion, apple-arbuscular mycorrhizal symbionts can effectively alleviate ARD by promoting plant growth and optimizing the structure of soil microbial communities. Future research, should test other gardening plants following AMF inoculation to prepare for a wider application in controlling replant disease. • Arbuscular mycorrhizal fungi can enhance the growth of young apple trees. • Apple-arbuscular mycorrhiza symbionts reduce the presence of Fusarium in replanted soil. • Clonostachys was a key differential species in the soil with mycorrhizal apple treatment. • AP, NO 4 + and NO 3 − drive the microbial communities in replanted soil. [ABSTRACT FROM AUTHOR]

• Ammonium bicarbonate can enhance the growth of replanted apple trees. • Ammonium bicarbonate reduces the presence of Fusarium in replanted soil. • Soil properties influence plant growth by altering fungal biomass and soil enzyme in replanted soil. Providing nitrogen is the core of increasing production in modern agricultural systems, as well as in the production of fruit trees. The rational application of nitrogen is an important measure to increase production and sustainably utilize agricultural ecosystems. Greenhouse, pot and field experiments were conducted to study the effects of different nitrogen forms on the antifungal effect in vitro , apple growth status and the soil environment under replant condition, aims to provide a basis for scientific fertilization and alleviates apple replant disease during orchard construction. We investigated the growth of apple in replant soil treated with different forms of nitrogen, including ammonium nitrogen (NH 4 N), nitrate nitrogen (NO 3 N) and amide nitrogen (CO(NH 2) 2). The results showed that ammonium bicarbonate can inhibit the mycelial growth, spore germination and toxins synthesis of soil-borne pathogens in vitro. The addition of ammonium bicarbonate significantly promoted the replanted apple growth. The activities of soil sucrase, urease, phosphatase and catalase were higher following treatment with ammonium bicarbonate than in the control soil. The qPCR analysis showed that the bacterial, fungal biomass differed distinctly between the different nitrogen forms and the control. These results suggest that ammonium bicarbonate can inhibit the mycelial growth, spore germination and toxins synthesis of soil-borne pathogens, improve the activities of soil enzymes and change soil microbial biomass. These changes can promote growth ofreplanted apple, thereby, ammonium bicarbonate can be used to alleviate apple replant disease as a new control measure. [ABSTRACT FROM AUTHOR]

Directional brightness temperature (DBT) acquired by remote sensing instruments plays a significant role in characterizing the directional anisotropy of land surface, especially for row canopies. The difference between shaded vegetation and sunlit vegetation is ignored in the existing models. In this article, a four-component parameterized directional thermal radiance model (FCPMod) has been proposed to describe the DBT of the row canopy by considering the four components including the sunlit/shaded soil and sunlit/shaded leaf, the improved multiple scattering within the canopy, and the sensor’s field of view (FOV). First, the sensor’s FOV is divided into many tiny rectangles along the row direction and the probabilities of four components in each tiny rectangle are estimated based on the radiative transfer (RT) theory and the bidirectional gap probability. Second, the DBTs are weighted by the four components’ probabilities and brightness temperatures of tiny rectangles. Third, a modified multiple scattering model is proposed to improve the modeling accuracy by considering the contribution of the multiple scattering radiance between soil and canopy. The sensitivity analysis results show that the proposed method performed well compared to the FRA97 model proposed by François et al. (1997) over continuous canopy and the RT model (FovMod) proposed by Ren et al. (2013) over row canopy. Finally, the field validations on a maize row canopy show that the proposed FCPMod performed better than about 0.4 K compared with the FovMod. [ABSTRACT FROM AUTHOR]

The advanced hyperspectral imager (AHSI) is one of the sensors aboard the Chinese Gaofen-5 (GF-5) satellite, possessing characteristics of high spatial and spectral resolution, as well as width swath. To better understand the radiometric performance of GF-5/AHIS after its launch, this article presents an on-orbit radiometric calibration approach for AHSI visible and near-infrared (VNIR) and shortwave infrared (SWIR) sensors from field automatic observations with a field spectrometer in the absence of SWIR measurements. A spectrum extension method was proposed to extend the retrieved surface hyperspectral reflectance in the VNIR spectral ranges to SWIR by incorporating the historical hyperspectral reflectance library. The radiometric calibration coefficients of GF-5/AHSI were calculated by linear fitting of the observed digital number (DN) values with GF-5/AHSI and predicted at-sensor radiances with MODTRAN 5 based on extended hyperspectral surface reflectance. Comparisons with onboard calibration results were also performed, and the averaged relative differences were within 5% with $1\delta $ standard deviations less than 10% for most bands, except for those in the atmospheric absorption and low signal-to-noise ratio bands. The comparison results indicate that the on-site radiometric calibration results are consistent with the onboard results, and the operational on-orbit radiometric calibration approach is reliable in the case that there are no measurements in the SWIR spectra range. The on-orbit radiometric performance of GF-5/AHSI rapidly degraded during the first several months after its launch and then tended to be relatively stable. [ABSTRACT FROM AUTHOR]

Climate observations and their applications require measurements with high stability and low uncertainty in order to detect and assess climate variability and trends. The difficulty with space-based observations is that it is generally not possible to trace them to standard calibration references when in orbit. In order to overcome this problem, it has been proposed to deploy space-based radiometric reference systems which intercalibrate measurements from multiple satellite platforms. Such reference systems have been strongly recommended by international expert teams. This paper describes the Chinese Space-based Radiometric Benchmark (CSRB) project which has been under development since 2014. The goal of CSRB is to launch a reference-type satellite named LIBRA in around 2025. We present the roadmap for CSRB as well as requirements and specifications for LIBRA. Key technologies of the system include miniature phase-change cells providing fixed-temperature points, a cryogenic absolute radiometer, and a spontaneous parametric down-conversion detector. LIBRA will offer measurements with SI traceability for the outgoing radiation from the Earth and the incoming radiation from the Sun with high spectral resolution. The system will be realized with four payloads, i.e., the Infrared Spectrometer (IRS), the Earth-Moon Imaging Spectrometer (EMIS), the Total Solar Irradiance (TSI), and the Solar spectral Irradiance Traceable to Quantum benchmark (SITQ). An on-orbit mode for radiometric calibration traceability and a balloon-based demonstration system for LIBRA are introduced as well in the last part of this paper. As a complementary project to the Climate Absolute Radiance and Refractivity Observatory (CLARREO) and the Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS), LIBRA is expected to join the Earth observation satellite constellation and intends to contribute to space-based climate studies via publicly available data. [ABSTRACT FROM AUTHOR]

The unique feature of the Visible Infrared Imager Radiometer Suite (VIIRS) day/night band (DNB) is its ability to take quantitative measurements of low-light scenes at night. In order to monitor the stability of the high gain stage (HGS) of the DNB, nighttime observations over the Dome C site under moonlight are analyzed in this study. The Miller and Turner 2009 (MT2009) lunar irradiance model has been used to simulate lunar illumination over Dome C. However, the MT2009 model does not differentiate the waxing and waning lunar phases. In this paper, the MT-SWC (SeaWiFS Corrected) lunar irradiance model differentiating the waxing and waning lunar phases is derived by correcting the MT2009 model using lunar observations made by the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS). In addition, a top of atmosphere (TOA) bi-directional reflectance distribution function (BRDF) model during nighttime over Dome C is developed to remove the angular dependence from the nighttime TOA reflectance. The long-term stability monitoring of the DNB high-gain stage (HGS) reveals a lower reflectance factor in 2012 in comparison to the following years, which can be traced back to the change in relative spectral response (RSR) of National Oceanic & Atmospheric Administration's (NOAA's) Interface Data Processing Segment (IDPS) VIIRS DNB in April 2013. It also shows the radiometric stability of DNB data, with long-term stability of less than 1.58% over the periods from 2013 to 2016. This method can be used to monitor the radiometric stability of other low-light observing sensors using vicarious calibration sites under moonlight illumination. [ABSTRACT FROM AUTHOR]

Tree peony (Paeonia suffruticosa Andr.), a traditional Chinese ornamental plant, is famous for its large, colorful, and fragrant flowers. Studies on tree peony have mainly focused on the improvement of flower color and the regulation of the flowering stage, but the molecular mechanisms controlling the formation of floral fragrance has yet to be understood. In this study, the aromatic tree peony variety 'High Noon' was used to determine whether volatile compounds (volatiles) in flowers were synthesized at the balloon, initial opening, half opening, or full opening stages. Transcriptomic sequencing was conducted on petals and stamens collected at the balloon and full opening stages. The relative content of linalool peaked during the full opening stage of flowering, and linalool was the main component of flower fragrance. As flowering progressed, the relative content of monoterpenes gradually increased and the relative content of sesquiterpenes gradually decreased. Transcriptome data revealed 23695 differentially expressed genes (DEGs), 142 of which were related to terpene accumulation. Transcriptome analysis and correlation analysis between floral volatiles and gene expressions showed that, 1-deoxy- d -xylulose 5- phosphate synthase (DXS), 1-deoxy- d -xylulose 5-phosphate reductoisomerase (DXR), acetyl-CoA acetyltransferase (AACT), geranyl pyrophosphate synthase (GPPS), and terpene synthase (TPS) may be major regulators controlling floral terpene biosynthesis in 'High Noon'. And PsGPPS may regulate the expression of GPPS, and then participate in the synthesis of terpenes. This study provides a possible molecular mechanism for terpene formation in tree peony 'High Noon' flowers as well as a theoretical basis upon which to study tree peony flowers. • Linalool, a monoterpene compound, is the main component of floral fragrance of aromatic tree peony variety 'High Noon'. • DXS, DXR, AACT, GPPS and TPS may be major regulators controlling floral terpene biosynthesis of tree peony. • PsGPPS may regulate the expression of GPPS, and then participate in the synthesis of terpenes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The population of Tamarix chinensis showed an aggregated distribution. • The aggregation intensity of T. chinensis decreased with increasing spatial scale. • Biological and environmental effects can affect the distribution of T. chinensis. • Soil water and salt content are the most important environmental factors. • The spatial distribution pattern of plant is helpful to the vegetation restoration. To explore the spatial distribution pattern of the Tamarix chinensis population and the influencing factors in the muddy coastal zone of Bohai Bay, we studied the T. chinensis forest on the beach of the muddy area of Beihai New District, Binzhou City, Shandong Province. A combination of field investigations and laboratory-based sample analyses were used to measure and analyze the forest density, height, cover, distance from the sea, groundwater depth, soil salinity, basic soil physical properties and soil nutrients. The results showed that the coefficients of variation for the 18 soil and forest indices for T. chinensis were between 0.03 and 0.96; the coefficients of variation for forest density, soil Ca2+ and Na+ content were the greatest, followed by those for soil Mg2+, soil salt content, distance from sea, and available phosphorus, while those for soil bulk density, total phosphorus, pH and other indicators changed less. The population of T. chinensis on the beach of the coastal zone of the Yellow River Delta showed an aggregated distribution, and its aggregation intensity decreased with increasing spatial scale, and it tended to evolve into a random distribution on a larger scale. The spatial distribution of the T. chinensis population showed a certain density dependence; that is, the greater the density was, the greater the aggregation intensity. The reason for the aggregated distribution of the T. chinensis population was mainly related to the biological characteristics of the organism itself or to the interactions between its biological characteristics and environmental factors. T. chinensis forest density was significantly and negatively correlated with organic carbon, total phosphorus, Ca2+, and Na+ (P < 0.05) and very significantly and negatively correlated with available phosphorus (P < 0.01). The soil water content was significantly and positively correlated with the soil salt content, K+, and Na+ (P < 0.01) and significantly and negatively correlated with the distance from the sea and groundwater depth (P < 0.05). The soil salt content was significantly and positively correlated with K+, Na+, and nitrate nitrogen (P < 0.01) and significantly and negatively correlated with distance from the sea and groundwater depth (P < 0.05). K+ and Na+ were the main cations contributing to soil salinity in this T. chinensis forest. With an increase in the distance from the sea, the groundwater depth and forest density gradually increased, and the soil water content and soil salt content gradually decreased. Soil water content, soil salt content, K+, and Na+ content were the dominant factors affecting the spatial distribution pattern for the T. chinensis population in the coastal tidal flat of the Yellow River Delta, followed by organic carbon, ammonia nitrogen, and finally the Mg2+, SO 4 2-, Cl- content, and distance from the sea. The population distribution pattern for T. chinensis was mainly affected by the water and salt conditions, which is a result of the long-term adaptation and evolution of the species within the coastal saline-alkaline environment. Therefore, in the planting management and protection of T. chinensis in the muddy coastal zone of Bohai Bay, we should try to maintain the aggregation growth characteristics of the population according to the adaptation mechanism and biological characteristics of different habitats and community types of T. chinensis , allowing other species to coexist with T. chinensis , and thus optimizing the habitat in the coastal zone. [ABSTRACT FROM AUTHOR]

Leaf area index (LAI) is a key variable for modeling energy and mass exchange between the land surface and the atmosphere. Inversion of physically based radiative transfer models is the most established technique for estimating LAI from remotely sensed data. This study aims to evaluate the suitability of the PROSAIL model for LAI estimation of three typical row crops (maize, potato, and sunflower) from unmanned aerial vehicle (UAV) hyperspectral data. LAI was estimated using a look-up table (LUT) based on the inversion of the PROSAIL model. The estimated LAI was evaluated against in situ LAI measurements. The results indicated that the LUT-based inversion of the PROSAIL model was suitable for LAI estimation of these three crops, with a root mean square error (RMSE) of approximately 0.62 m 2 m −2 , and a relative RMSE (RRMSE) of approximately 15.5%. Dual-angle observations were also used to estimate LAI and proved to be more accurate than single-angle observations, with an RMSE of approximately 0.55 m 2 m −2 and an RRMSE of approximately 13.6%. The results demonstrate that additional directional information improves the performance of LAI estimation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phyllosphere bacteria community is closely related to leaf microtopography. • Leaf vein density is one dominant factor influencing phyllosphere bacteria community. • The larger leaf vein density leads to the higher stability of bacteria community. Phyllosphere bacteria are an important component of environmental microbial communities and are closely related to plant health and ecosystem stability. However, the relationships between the inhabitation and assembly of phyllosphere bacteria and leaf microtopography are still obscure. In this study, the phyllosphere bacterial communities and leaf microtopographic features (vein density, stomatal length, and density) of eleven tree species were fully examined. Both the absolute abundance and diversity of phyllosphere bacterial communities were significantly different among the tree species, and leaf vein density dominated the variation. TITAN analysis showed that leaf vein density also played more important roles in regulating the relative abundance of bacteria than stomatal features, and 6 phyla and 62 genera of phyllosphere bacteria showed significant positive responses to leaf vein density. Moreover, LEfSe analysis showed that the leaves with higher vein density had more bacterial biomarkers. Leaf vein density also changed the co-occurrence pattern of phyllosphere bacteria, and the co-occurrence network demonstrated more negative correlations and more nodes on the leaves with larger leaf vein density, indicating that higher densities of leaf veins improved the stability of the phyllosphere bacterial community. Phylogenetic analysis showed that deterministic processes (especially homogeneous selection) dominated the assembly process of phyllosphere bacterial communities. The leaf vein density increased the degree of bacterial clustering at the phylogenetic level. Therefore, the inhabitation and assembly of the phyllosphere bacterial community are related to leaf microtopography, which provides deeper insight into the interaction between plants and bacteria. [ABSTRACT FROM AUTHOR]

• R. pseudoacacia increased the fine particles and reduced coarse particles content. • R. pseudoacacia significantly reduced D 0 , D 1 , D 2 but increased Δα and Δf. • R. pseudoacacia suppress the coarsening and deterioration of the surface. The soil particle size distribution (PSD) is a fundamental physical property that can affect soil nutrients, soil structure characterization and soil hydraulic properties. However, the effect of plant expansion on soil PSD is not clear. Therefore, in this study, fractal theory was applied to quantitatively describe the PSD. On Mount Tai, artificial afforestation with Robinia pseudoacacia is helpful in restoring ecosystems and improving soil quality. However, clonal spread allows R. pseudoacacia to easily escape cultivation, leading to the formation of mixed forests. Therefore, exploring the effect of R. pseudoacacia expansion on soil PSD is important. The results show that 1) R. pseudoacacia expansion increased the clay and silt contents and reduced the sand content; 2) R. pseudoacacia expansion significantly reduced the capacity dimension, entropy dimension, and correlation dimension and increased the width and asymmetry of the singularity spectra but was unrelated to the entropy dimension/capacity dimension; and 3) the capacity dimension was significantly positively correlated with the sand content and significantly negatively correlated with the silt and clay contents, but the asymmetry of the soil PSD was inconsistent with the capacity dimension. In summary, R. pseudoacacia can reduce the heterogeneity of the PSD by increasing the distribution range and density of the PSD. Our results provide important insight into the effect of plant expansion on soil PSD. [ABSTRACT FROM AUTHOR]

Abstract: The Surface Energy Balance Algorithm for Land (SEBAL) has been successfully applied to remote sensing data to estimate surface evapotranspiration (ET) at different spatial and temporal resolutions in more than 30 countries. However, the selection of dry and wet pixels over the area of interest (AOI) makes the SEBAL-estimated ET subject to the sizes of the AOI and the satellite pixels. This paper investigates the effect of the sizes of the AOI and satellite pixels on SEBAL-derived surface energy components by proposing generalized analytical equations. These equations demonstrate how the variations in the intermediate variables, the AOI, and the pixel size affect the resulting surface energy components and under which circumstances the sensible heat flux will be misestimated, without needing to run the SEBAL model. These analytical equations were verified through application to 23 clear-sky MODIS overpasses that cover different soil water contents and crop growth stages from January 2010 to late October 2011. The spatial effects of increasing the size of the AOI for SEBAL can be summarized as follows: (1) if the locations of dry and wet pixels do not vary, the pixel-by-pixel sensible heat flux (H LA ) calculated using the larger AOI is equal to that of the smaller AOI (H SA , with H LA /H SA =1), (2) if only the surface temperatures of wet pixels do not vary, the relative variation in H is equal to the relative variation of the slope (a) of the linear equation between the near-surface air temperature difference and the surface temperature (H LA /H SA =1+ δH SA /H SA =1+ δa/a), and (3) under other circumstances, H LA /H SA decreases with surface temperatures at a slowing pace from ∼∞ at the temperature of the wet pixel (T s,wet ) to a certain value at the temperature of the dry pixel (T s,dry ) (both temperatures are for the small AOI). Analogously, a general analytical equation—a function of the coefficients of the linear equation between the near-surface air temperature difference and surface temperature at the high-resolution, the effective temperature, and the effective momentum roughness length—could be used to quantify the spatial-scale effect of the satellite pixel size. The findings from this study may help determine suitable sizes of the AOIs and the satellite pixels and aid in quantifying uncertainties in the SEBAL-derived surface energy components. [Copyright &y& Elsevier]

To evaluate the in-flight performance of a new hyperspectral sensor onboard an unmanned aerial vehicle (UAV-HYPER), a comprehensive field campaign was conducted over the Baotou test site in China on 3 September 2011. Several portable reference reflectance targets were deployed across the test site. The radiometric performance of the UAV-HYPER sensor was assessed in terms of signal-to-noise ratio (SNR) and the calibration accuracy. The SNR of the different bands of the UAV-HYPER sensor was estimated to be between approximately 5 and 120 over the homogeneous targets, and the linear response of the apparent reflectance ranged from approximately 0.05 to 0.45. The uniform and non-uniform Lambertian land surface reflectance was retrieved and validated using in situ measurements, with root mean square error (RMSE) of approximately 0.01–0.07 and relative RMSE of approximately 5%–12%. There were small discrepancies between the retrieved uniform and non-uniform Lambertian land surface reflectance over the homogeneous targets and under low aerosol optical depth (AOD) conditions (AOD = 0.18). However, these discrepancies must be taken into account when adjacent pixels had large land surface reflectance contrast and under high AOD conditions (e.g. AOD = 1.0). [ABSTRACT FROM AUTHOR]

This article compares one- and two-source energy balance (OSEB and TSEB) models in the estimates of surface energy components using Landsat imagery and surface measurements acquired from an experimental field at Yucheng Station in Northern China. Compared to surface measurements, similar performance between the TSEB and OSEB models has been observed for estimated surface net radiation and soil heat flux. The root mean square difference (RMSD) is within 14–39 W m−2in both the TSEB and OSEB models. The residual energy (ER) correction method yields the best agreement in comparisons of the sensible (H) and latent (LE) heat fluxes estimated using both the TSEB and OSEB models to the eddy covariance (EC) system measurements. The TSEB model is shown to greatly outperform the OSEB model in reproducing surfaceHandLEmeasurements. Cirrus clouds are likely responsible for the surface temperature retrieved from the enhanced thematic mapper plus (ETM+) sensor being lower than air temperature on days of the year (DOYs) 178 and 218 of 2009. This atmospheric stability is contrary to the unstable atmosphere that the EC measurements observe. If data on these two days are excluded and theERcorrection method is applied, when comparing the estimatedHandLEto the EC measurements, RMSD is within 55 W m−2in the TSEB model and is larger than 97 W m−2in the OSEB model. [ABSTRACT FROM PUBLISHER]

Land surface temperature (LST), land surface emissivity (LSE), and atmospheric profiles are of great importance in many applications. Radiances observed by satellites depend not only on land surface parameters (LST and LSE) but also on atmospheric conditions, and it is difficult to retrieve these parameters simultaneously from multispectral measurements with high accuracies. This work aims to establish a neural network (NN) to retrieve atmospheric profiles, LST, and LSE simultaneously from hyperspectral thermal infrared data suitable for various air mass types and surface conditions. The distributions of surface materials, LST, and atmospheric profiles were elaborated carefully to generate the simulated data. The simulated at-sensor radiances were divided into two sub-ranges in the spectral domain: one in the atmospheric window and the other in the water absorption band. Subsequently, the radiances were transformed in the eigen-domain in each sub-range, and then the transformed coefficients were used as the inputs for the network. Similarly, the atmospheric profiles, LST, and LSE were used as outputs after the eigen-domain transformation. The validation of the NN using the simulated data indicated that the root mean square error (RMSE) of LST is approximately 1.6 K, and the RMSE of the temperature profiles is approximately 2 K in the troposphere. Meanwhile, the RMSE of total water content is approximately 0.3 g cm−2, and that of LSE is less than 0.01 in the spectral interval where the wave number is less than 1000 cm−1. Two experiments using actual thermal hyperspectral satellite data were carried out to further validate the proposed NN. All of these studies showed that the proposed NN is capable of retrieving atmospheric and land surface parameters with compromised accuracies. Because of its simplicity, the proposed NN can be used to yield preliminary results employed as first estimates for physics-based retrieval models. [ABSTRACT FROM PUBLISHER]

Abstract: This paper compares three remote sensing-based models for estimating evapotranspiration (ET), namely the Surface Energy Balance System (SEBS), the Two-Source Energy Balance (TSEB) model, and the surface temperature–vegetation index Triangle (TVT). The models used as input MODIS/TERRA products and ground measurements collected during the wheat and corn growth period in a subhumid climate at a measurement station in Yucheng, China. MODIS land surface temperature (LST) and leaf area index (LAI) products, corrected using ground-truth observations, were used in the three models. The TSEB model output of sensible (H) and latent (LE) heat fluxes were in good agreement with Large Aperture Scintillometer (LAS)-measured H and LE derived by residual (RMSD<45W/m2). Reasonable agreement was also obtained with the SEBS model output yielding RMSD for H of ~40W/m2 and LE ~55W/m2. However, the TVT model output resulted in poor agreement with the LAS-estimated H and LE with RMSD-values >110W/m2. Using the uncorrected MODIS LST and LAI products resulted in a deterioration of the agreement in H and LE with LAS-estimated values for both the TSEB and SEBS models, whereas TVT performance improved marginally. These results indicate that the TSEB model yielded the closest agreement with the LAS-estimated fluxes using either the corrected or uncorrected MODIS inputs (LST and LAI). The SEBS model also computed reasonable H and LE values but was significantly more sensitive to errors in MODIS LST and LAI inputs than the TSEB model. In the TVT model, output of H and LE was unacceptable in either scenario of MODIS input which was attributable to errors in selection of the dry edge. With the TVT method, accurate determination of the dry edge end member is critical in regional ET estimation, but for humid and subhumid regions this end member may often be quite difficult to identify or encompass within a satellite scene. [Copyright &y& Elsevier]

Owing to the ill-posed problem of radiometric equations, the separation of land surface temperature (LST) and land surface emissivity (LSE) from observed data has always been a troublesome problem. On the basis of the assumption that the LSE spectrum can be described by a piecewise linear function, a new method has been proposed to retrieve LST and LSE from atmospherically corrected hyperspectral thermal infrared data using linear spectral emissivity constraint. Comparisons with the existing methods found in literature show that our proposed method is more noise immune than the existing methods. Even with a \NE\Delta \T of 0.5 K, the rmse of LST is observed to be only 0.16 K, and that of LSE is 0.006. In addition, our proposed method is simple and efficient and does not encounter the problem of singular values unlike the existing methods. As for the impact of the atmosphere, the results show that our proposed method performs well with the uncertainty of the atmospheric downwelling radiance but suffers from the inaccuracy of the atmospheric upwelling radiance and atmospheric transmittance, which implies that an accurate atmospheric correction is still needed to convert the radiance measured at the satellite level to the at-ground radiance. To validate the proposed method, a field experiment was conducted, and the results show that 80% of the samples have an accuracy of LST within 1 K and that the mean values of LSE are accurate to 0.01. [ABSTRACT FROM AUTHOR]

Monitoring vertical profile of leaf water content (LWC) within wheat canopies after head emergence is vital significant for increasing crop yield. However, the estimation of vertical distribution of LWC from remote sensing data is still challenging due to the effects of wheat spikes and the efficacy of sensor measurement from the nadir direction. Using two-year field experiments with different growth stages after head emergence, N rates, wheat cultivars, we investigated the vertical distribution of LWC within canopies, the changes of canopy reflectance after spikes removal, the relationship between spectral indices and LWC in the upper-, middle- and bottom-layer. The interrelationship among vertical LWC were constructed, and four ratio of reflectance difference (RRD) type of indices were proposed based on the published WI and NDWSI indices to determine vertical distribution of LWC. The results indicated a bell shape distribution of LWC in wheat plants with the highest value appeared at the middle layer, and significant linear correlations between middle-LWC vs. upper-LWC and middle-LWC vs. bottom-LWC (r ≥ 0.92) were identified. The effects of wheat spikes on spectral reflectance mainly occurred in near infrared to shortwave infrared regions, which then decreased the accuracy of LWC estimation. Spectral indices at the middle layer outperformed the other two layers in LWC assessment and were less susceptible to wheat spikes effects, in particular, the newly proposed narrow-band WI-4 and NDWSI-4 indices exhibited great potential in tracking the changes of middle-LWC (R2 = 0.82 and 0.84, respectively). By taking into account the effects of wheat spikes and the interrelationship of vertical LWC within canopies, an indirect induction strategy was developed for modeling the upper-LWC and bottom-LWC. It was found that the indirect induction models based on the WI-4 and NDWSI-4 indices were more effective than the models obtained from conventional direct estimation method, with R2 of 0.78 and 0.81 for the upper-LWC estimation, and 0.75 and 0.74 for the bottom-LWC estimation, respectively. [ABSTRACT FROM AUTHOR]

Using physical (acoustical engineering mechanics and scanning electron microscope) and other technical methods, is study makes a comprehensive analysis of the structural characteristics and engineering mechanics properties of sediments, the sediment structure, microstructure and their classification characteristics and in the light of the physical-mechanical characteristic parameters, the relations between the grain contact, grain accumulation, and porosity with the physical-mechanical characteristics of sediment, and reports the relationship between the acoustic physical parameters and the stress-strain properties of sediment. Results show that there are six structural types in the shelf seabed sediment of the northern South China Sea, among which, the mixed contact structural type sediment has a higher compressive strength and a higher sound velocity than others, and that in the shallow seabed there exists a mesoscale structure with high and low velocity layers. [ABSTRACT FROM AUTHOR]

The field of view (FOV) of pushbroom hyperspectral imager is limited by the compromise of the detector scale and requirements of spatial resolution. Combining imagers along the sampling direction effectively expands its FOV and improves the imaging efficiency. Due to the small overlapping area between the adjacent imagers, stitching the images using traditional methods need a large amount of ground control points (GCPs) or additional strips, which reduce the efficiency of both image acquisition and processing. This paper proposed a new method to precisely stitch images acquired from multiple pushbroom imagers. First, the relative orientation model was built based on the homonymy points to calculate the relative relationship between the adjacent imagers. Then rigorous geometric imaging model was adopted to generate a seamless stitching image. Simulation data was used to verify the accuracy of the method and to quantitatively analyze the effect of different error sources. Results show that the stitching accuracy is better than two pixels. Overall, this method provides a novel solution for stitching airborne multiple pushbroom images, to generate the seamless stitching image with wide FOV. [ABSTRACT FROM AUTHOR]

Field calibration is a feasible way to evaluate space-borne optical sensor observations via natural or artificial sites on Earth's surface with the aid of synchronous surface and atmospheric characteristic data. Since field calibration is affected by the coupled effects of surface and atmospheric characteristics, the single calibration results acquired under different surface and atmospheric conditions have different biases and different uncertainties, making it difficult to determine the consistency of these multiple calibration results. In view of this, by assuming that the radiometric performance is invariant during field calibration and the calibration samples are independent of each other, the surface–atmosphere invariant Key Comparison Reference Value (KCRV) is essentially derived from various calibration results. As the number of calibration samples increases, the uncertainty in the KCRV should decrease, and the KCRV should approach the "true" value. This paper addresses a novel method for estimating a weighted average value from multiple calibration results that can be used to compare each calibration result, and this value is accepted as the KCRV. Furthermore, this method is preliminarily applied to the field calibration of the Multispectral Instrument (MSI) onboard the Sentinel-2B satellite via the desert target at the Baotou site, China. After employing a chi-squared test to verify that 12 calibration samples are independent from each other, the KCRV of the 12 calibration samples at the Baotou site is derived, which exhibits much lower uncertainty than a single sample. The results show that the KCRVs of the relative differences between the simulated and observed at-sensor reflectance are 3.75%, 5.11%, 6.09%, and 5.03% for the four bands of Sentinel-2B/MSI, respectively, and the corresponding uncertainties are 1.84%, 1.87%, 1.90%, and 1.93%. It is noted that the KCRV uncertainty obtained with only 12 calibration samples is reduced significantly, and in the future, more samples in other instrumented sites will be used to validate this method thoroughly. [ABSTRACT FROM AUTHOR]

A new flavanone glycoside, (2 S)5,7,4′-trihydroxyflavanone-8- C-β-D-(6″- O-acetyl)glucopyranoside ( 1), together with six known flavonoids, isohemiphloin ( 2), vitexin ( 3), cirsimaritin ( 4), hispidulin ( 5), apigenin ( 6), and eupatorin ( 7), was isolated from the leaves and stems of Abrus precatorius. Their structures were elucidated on the basis of physical and spectral analysis. Rotamers exist for compounds 1, 2, and 3. Compounds 1-3, 6, and 7 were isolated from this plant for the first time. [ABSTRACT FROM AUTHOR]

Vicarious calibration and validation techniques are important tools to ensure the long-term stability and inter-sensor consistency of satellite sensors making observations in the solar-reflective spectral domain. Automated test sites, which have continuous in situ monitoring of both ground reflectance and atmospheric conditions, can greatly increase the match-up possibilities for a wide range of space agency and commercial sensors. The Baotou calibration and validation test site in China provides operational high-accuracy and high-stability vicarious calibration and validation for high spatial resolution solar-reflective remote-sensing sensors. Two sites, given the abbreviations BTCN (an artificial site) and BSCN (a natural sandy site), have been selected as reference sites for the Committee on Earth Observation Satellites radiometric calibration network (RadCalNet). RadCalNet requires sites to provide data in a consistent format but does not specify the required operational conditions for a RadCalNet site. The two Baotou sites are the only sites to date that make spectral measurements for their continuous operation. One of the core principles of RadCalNet is that each site should have a metrologically rigorous uncertainty budget which also describes the site's traceability to the international system of units, the SI. This paper shows a formalized metrological approach to determining and documenting the uncertainty budget and traceability of a RadCalNet site. This approach follows the Guide to the Expression of Uncertainty in Measurement. The paper describes the uncertainty analysis for bottom-of-atmosphere and top-of-atmosphere reflectance in the spectral region from 400 to 1000 nm for the Baotou sites and gives preliminary results for the uncertainty propagating this to top-of-atmosphere reflectance. [ABSTRACT FROM AUTHOR]

Hyperspectral LiDAR (HSL) technology can obtain spectral and ranging information from targets by processing the recorded waveforms and measuring the time of flight (ToF). With the development of the supercontinuum laser (SCL), it is technically easier to develop an active hyperspectral LiDAR system that can simultaneously collect both spatial information and extensive spectral information from targets. Compared with traditional LiDAR technology, which can only obtain range and intensity information at the selected spectral wavelengths, HSL detection technology has demonstrated its potential and adaptability for various quantitative applications from its spectrally resolved waveforms. However, with most previous HSLs, the collected spectral information is discrete, and such information might be insufficient and restrict the further applicability of the HSLs. In this paper, a tunable HSL technology using an acousto-optic tunable filter (AOTF) as a spectroscopic device was proposed, designed, and tested to address this issue. Both the general range precision and the accuracy of the spectral measurement were evaluated. By tuning the spectroscopic device in the time dimension, the proposed AOTF-HSL could achieve backscattered echo with continuous coverage of the full spectrum of 500–1000 nm, which had the unique characteristics of a continuous spectrum in the visible and near infrared (VNIR) regions with 10 nm spectral resolution. Yellow and green leaves from four plants (aloe, dracaena, balata, and radermachera) were measured using the AOTF-HSL to assess its feasibility in agriculture application. The spectral profiles measured by a standard spectrometer (SVC© HR-1024) were used as a reference for evaluating the measurements of the AOTF-HSL. The difference between the spectral measurements collected from active and passive instruments was minor. The comparison results show that the AOTF-based consecutive and high spectral resolution HSL was effective for this application. [ABSTRACT FROM AUTHOR]