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Coupled retrieval of the three phases of water from spaceborne imaging spectroscopy measurements
摘要： Measurements of reflected solar radiation by imaging spectrometers can quantify water in different states (solid, liquid, gas) thanks to the discriminative absorption shapes. We developed a retrieval method to quantify the amount of water in each of the three states from spaceborne imaging spectroscopy data, such as those from the German EnMAP mission. The retrieval couples atmospheric radiative transfer simulations from the MODTRAN5 radiative transfer code to a surface reflectance model based on the Beer-Lambert law. The model is inverted on a per-pixel basis using a maximum likelihood estimation formalism. Based on a unique coupling of the canopy reflectance model HySimCaR and the EnMAP end-to-end simulation tool EeteS, we performed a sensitivity analysis by comparing the retrieved values with the simulation input leading to an R2 of 0.991 for water vapor and 0.965 for liquid water. Furthermore, we applied the algorithm to airborne AVIRIS-C data to demonstrate the ability to map snow/ice extent as well as to a CHRIS-PROBA dataset for which concurrent field measurements of canopy water content were available. The comparison between the retrievals and the ground measurements showed an overall R2 of 0.80 for multiple crop types and a remarkable clustering in the regression analysis indicating a dependency of the retrieved water content from the physical structure of the vegetation. In addition, the algorithm is able to produce smoother and more physically-plausible water vapor maps than the ones from the band ratio approaches used for multispectral data, since biases due to background reflectance are reduced. The demonstrated potential of imaging spectroscopy to provide accurate quantitative measures of water from space will be further exploited using upcoming spaceborne imaging spectroscopy missions like PRISMA or EnMAP.
关键词： Atmospheric correction,EnMAP,Canopy water content,Water vapor,Imaging spectroscopy
更新于2025-09-23 15:21:01
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A high performance method for the accurate and precise determination of silicon isotopic compositions in bulk silicate rock samples using laser ablation MC-ICP-MS
摘要： MC-ICP-MS has become one of the most powerful analytical methods for Si isotopes in bulk liquid and solid samples in the past decade. Laser ablation provides direct sampling of solid samples, avoiding laborious chemical digestion procedures. As for powder bulk samples, the preparation of stable and homogeneous targets prior to measurements, and strategies to minimize potential matrix effects, are critical for accurate isotopic analysis. In this study, an accurate and precise method for Si isotope ratio measurements by fs-LA-MC-ICP-MS of bulk silicate rock samples was established. A new laser fusion sample preparation technique was developed to achieve fast and homogeneous fusion of silicate rock powders (including granite and granodiorite that contain abundant refractory minerals) into glasses. Compared to the pressed pellet technique, the measurement precision for fused glasses was improved ~5.7-fold. Matrix effects during Si isotopic analysis were observed when using non-matrix matched calibration protocols under normal dry-plasma instrument conditions with both ns- and fs-laser using a raster ablation mode. Matrix effects were eliminated by the addition of water vapor into the plasma, realizing accurate non-matrix matched calibration. In addition, fs-laser provided better measurement precisions, with the internal and external precisions being improved ~1.85 and ~2.4 fold compared to ns-laser at nearly equal signal intensities. Five well characterized silicate rock reference materials were analyzed using fs-LA-MC-ICP-MS calibrated against NBS-28 and BHVO-2G. Results obtained for =29Si and =30Si for these five reference materials were in agreement with previously reported values, confirming the accuracy of the proposed method.
关键词： matrix effects,Silicon isotopic analysis,water vapor addition,laser ablation MC-ICP-MS,silicate rock samples
更新于2025-09-23 15:21:01
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Bare Silica Opals for Real-Time Humidity Sensing
摘要： The photonic properties of 3D colloidal crystals made of St?ber silica spheres are shown to significantly depend on the relative humidity of the environment. The photonic bandgap of bare artificial opals formed by hydrophilic silica markedly varies in humid air along the entire range of water vapor concentration without the need for infiltration of functionalization. The optical changes are highly sensitive to humidity variation (especially in low-humidity range) and very fast response times of 60 ms, mainly ascribed to the absence of intermediate processes, the favorable bandgap characteristics (high intensity and sharp edges) and the high air accessibility to the open opal voids. Contrary to common approaches for photonic crystal sensors—seeking visual detection via large spectral shifts but having important shortcomings,—it is demonstrated that the well-defined photonic bandgap of bare silica opals allows, even for moderate shifts, outstanding sensing performance by proper monitoring with inexpensive equipment (no spectroscopic detection is needed). As a result, the rapid and reproducible photonic response enables accurate, real-time retrieval of the ambient humidity. The economical, one-step fabrication, and the efficient performance make silica artificial opals suitable for a new type of precise, low-cost, and real-time humidity sensors.
关键词： water vapor adsorption/desorption,real-time sensing,humidity sensors,artificial silica opals,photonic colloidal crystals
更新于2025-09-23 15:21:01
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Dealing with Climate Parameters in the Fabrication of Perovskite Solar Cells under Ambient Conditions
摘要： Although perovskite solar cells have demonstrated impressive efficiencies in research laboratories (above 25%), there is a need for experimental procedures to fabricate solar cells under ambient conditions to substantially decrease manufacturing costs. Nevertheless, to achieve efficient and highly stable devices in these conditions, the moisture level in the atmosphere must be monitored. The relative humidity (RH) has classically been the parameter of choice; however, in this work we show that the parameter of relevance is the absolute content of water measured in the form of partial water vapour pressure (WVP). To highlight the importance of this parameter, we demonstrate that small changes in ambient temperature at the same RH result in huge changes in solar cell performance. This is due to the non-linear dependence of the WVP on temperature (according to the Clausius-Clapeyron equation), and explains the dispersion of results found in the literature for devices nominally made at the same ambient RH levels. To illustrate this critical effect, we have deposited MAPbI3 perovskite films at different WVP values, which were derived from the climate parameters, RH and laboratory temperature, present during fabrication (not controlled). Hence, we adapt the fabrication method to the ambient conditions by monitoring the WVP, which allows for the fabrication of MAPbI3 based devices with efficiencies of up to 18.2% outside the glove box. In fact, we have extended the procedure to accomplish high-efficiency FA0.83MA0.17PbI3 devices under ambient conditions by adjusting the DMSO proportion in the perovskite precursor solution to the WVP.
关键词： Water Vapor Pressure,High Efficiency,Perovskite solar cells,Clausius-Clapeyron equation,Ambient Conditions
更新于2025-09-23 15:19:57
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Nanoconfined water vapour as a probe to evaluate plasmonic heating
摘要： Engineering the photothermal effect in plasmonic materials is of paramount importance for many applications such as cancer therapy, chemical synthesis, cold catalysis and more recently for metasurfaces. Evaluation of plasmonic heating at the nanoscale is challenging and generally requires sophisticated equipments and/or temperature-sensitive probes such as fluorescent molecules or materials. Here we propose to use water vapor as probe to evaluate the local heating around plasmonic nanoparticles. We demonstrated the concept for the case of a plasmonic colloidal film composed by a bi-modal nanoporosity. In particular we exploit the thermal and light water liquid-vapor phase transitions taking place into the nanoporous medium that can be triggered by external stimulus such as heating or irradiation to obtain structural and optical variations in the films. Estimation of the local temperature was then obtained by using spectroscopic ellipsometry acquired by a multimodal chamber. More generally, this method offer a simple and general approach to determine local temperature that only requires a nanoporous material and water vapor, such as environmental humidity. In addition this approach can be further generalized to other materials, vapor molecules or optical technique.
关键词： local temperature measurement,spectroscopic ellipsometry,water vapor,nanoporous materials,plasmonic heating
更新于2025-09-23 15:19:57
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Spectral Line Shape Analysis Using Hartmann-Tran Profile for Tunable Diode Laser Absorption Spectroscopy of Water Vapor at 1.39a????m
摘要： In this study, spectral line shape analysis was conducted for water vapor absorption at 1.39 μm with a Hartmann-Tran pro?le (HTP), which is capable of being ef?ciently and accurately reduced to (speed dependent) Voigt and (speed dependent) Rautian pro?les. The near-IR absorption lines of water vapor were measured using tunable diode laser absorption spectroscopy (TDLAS). The spectrum ?tting code was home-written based on the Trust region re?ective algorithm and the HTP. Voigt pro?le (VP), Rautian pro?le (RP), speed-dependent VP (SDVP), and speed-dependent Rautian pro?le (SDRP), which were reduced from the HTP, were used as model functions to test the validity of the near-IR absorption lines of water vapor in terms of line shape pro?le. With the SDVP, the standard deviation of the ?tting residuals was at a 10?3 level relative to the most intense peak height in a range of 1.39 μm at 2.5 Torr and room temperature, while the global standard deviation was less than 0.5 × 10?3, thus showing the best result among them. This suggests the need to consider the speed-dependent collision width in the self-broadening of water vapor.
关键词： Tunable diode laser absorption spectroscopy,Hartmann-Tran pro?le,Spectral lineshape analysis,Water vapor
更新于2025-09-23 15:19:57
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Combining Meteosat-10 satellite image data with GPS tropospheric path delays to estimate regional integrated water vapor (IWV) distribution
摘要： Using GPS satellites signals, we can study different processes and coupling mechanisms that can help us understand the physical conditions in the lower atmosphere, which might lead or act as proxies for severe weather events such as extreme storms and flooding. GPS signals received by ground stations are multi-purpose and can also provide estimates of tropospheric zenith delays, which can be converted into accurate integrated water vapor (IWV) observations using collocated pressure and temperature measurements on the ground. Here, we present for the first time the use of Israel’s dense regional GPS network for extracting tropospheric zenith path delays combined with near-real-time Meteosat-10 water vapor (WV) and surface temperature pixel intensity values (7.3 and 10.8 μm channels, respectively) in order to assess whether it is possible to obtain absolute IWV (kg m?2) distribution. The results show good agreement between the absolute values obtained from our triangulation strategy based solely on GPS zenith total delays (ZTD) and Meteosat-10 surface temperature data compared with available radiosonde IWV absolute values. The presented strategy can provide high temporal and special IWV resolution, which is needed as part of the accurate and comprehensive observation data integrated in modern data assimilation systems and is required for increasing the accuracy of regional numerical weather prediction systems forecast.
关键词： GPS,numerical weather prediction,integrated water vapor,tropospheric zenith delays,Meteosat-10
更新于2025-09-23 15:19:57
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An LM-BP Neural Network Approach to Estimate Monthly-Mean Daily Global Solar Radiation Using MODIS Atmospheric Products
摘要： Solar energy is one of the most widely used renewable energy sources in the world and its development and utilization are being integrated into people’s lives. Therefore, accurate solar radiation data are of great significance for site-selection of photovoltaic (PV) power generation, design of solar furnaces and energy-efficient buildings. Practically, it is challenging to get accurate solar radiation data because of scarce and uneven distribution of ground-based observation sites throughout the country. Many artificial neural network (ANN) estimation models are therefore developed to estimate solar radiation, but the existing ANN models are mostly based on conventional meteorological data; clouds, aerosols, and water vapor are rarely considered because of a lack of instrumental observations at the conventional meteorological stations. Based on clouds, aerosols, and precipitable water-vapor data from Moderate Resolution Imaging Spectroradiometer (MODIS), along with conventional meteorological data, back-propagation (BP) neural network method was developed in this work with Levenberg-Marquardt (LM) algorithm (referred to as LM-BP) to simulate monthly-mean daily global solar radiation (M-GSR). Comparisons were carried out among three M-GSR estimates, including the one presented in this study, the multiple linear regression (MLR) model, and remotely-sensed radiation products by Cloud and the Earth’s radiation energy system (CERES). The validation results indicate that the accuracy of the ANN model is better than that of the MLR model and CERES radiation products, with a root mean squared error (RMSE) of 1.34 MJ·m?2 (ANN), 2.46 MJ·m?2 (MLR), 2.11 MJ·m?2 (CERES), respectively. Finally, according to the established ANN-based method, the M-GSR of 36 conventional meteorological stations for 12 months was estimated in 2012 in the study area. Solar radiation data based on the LM-BP method of this study can provide some reference for the utilization of solar and heat energy.
关键词： precipitable water vapor,solar radiation,LM-BP neural network,aerosols,clouds
更新于2025-09-19 17:15:36
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Compact dual-gas sensor for simultaneous measurement of atmospheric methane, and water vapor using a 3.38?μm antimonide-distributed feedback laser diode
摘要： A simple, compact sensor involving a continuous-wave 3.38 mm distributed feedback laser in combination with a novel compact dense-pattern multipass cell was demonstrated for simultaneous measurement of atmospheric methane and water vapor. The calibration-free direct absorption spectroscopy approach was adopted for data generation and processing. Allan deviation analysis indicates that minimum detection limits (1s) of 11.0 ppb for CH4 and 100 ppm for H2O were achieved with a 1-s integration time at an optimum pressure of 50 Torr. Atmospheric environmental mixing ratios of these two gases were recorded and analyzed. This newly developed mid-infrared dual-gas sensor is very suitable for trace gas sensing in weight-limited unmanned aerial vehicle- or balloon-embedded field observations.
关键词： Multipass cell,Laser sensors,Water vapor,Distributed feedback laser,Laser absorption spectroscopy,Methane
更新于2025-09-19 17:13:59
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P‐9.1: QD based color converter with DBR Structure and its application on Micro‐LED
摘要： An enhancement of light extraction efficiency of quantum dots (QD) (LEDs) with Bi-functional TiO2/Al2O3 distributed Bragg reflector (DBR) nanolaminate structure grown by atomic layer deposition (ALD) has been demonstrated. The DBRs were simulated and optimized with TFCalc, and they exhibited excellent and tunable optical properties, as well as reliable moisture barrier performance. These DBRs were integrated in the QD-LED, enabling an obvious increase in red emission and a strong decrease in blue light transmittance, which can achieve color conversion greatly. Furthermore, these DBRs can prolong the lifetime of QDs evidently by isolating the QDs from the moisture vapor. These results highlight the potential application of DBRs in the QLEDs and QD-LEDs.
关键词： atomic layer deposition (ALD),simulation,distributed Bragg reflector (DBR),water vapor transmission rates (WVTR),light extraction efficiency
更新于2025-09-19 17:13:59