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The papers in this special section examine the use of remote sensing technology to promote environmental sustainability in Asia-Pacific regions. Worldwide urbanization and deforestation are the two main interconnected ways that human activities are continually changing and reshaping the earth's surface. How earth observation and remote sensing technologies can contribute to improve the knowledge of the productivity and sustainability of natural and human ecosystems is an important theme in the global change community. In China, for instance, rapid economic growth and urbanization over the past three decades have resulted in dramatic changes in land use and land cover and have led to severe environmental consequences, which have made China's sustainable development a grand challenge. In the meantime, during the past few decades, environmental changes in the Asian–Pacific region have posed significant challenges to the scientific community. Therefore, the global problem of how earth observation and remote sensing technologies may be applied to assessing, monitoring, modeling, and simulating ecosystems, environments, and resources at various spatial and temporal scales translates into peculiar and very urgent questions and applications in this colossal and dynamic geographical region. [ABSTRACT FROM AUTHOR]

Acoustic underwater sensor network (UWSN) is important in terms of business and for military applications. Optimum UWSN design provides a reliable connection with maximum connectivity, minimal multipath, low technical cost, and emphasis on energy conservation. This paper examines the channel estimation parameters, such as channel impulse response, coherence bandwidth, BER due to delay for differentially detected MSK receiver, and transmission loss impact of underwater node placement in three scenarios (ground-based, buoys-based, and horizontal point-to-point sensor node). All data (bathymetry, altimetry, temperature, salinity, and depth) are real and have been sourced from different satellite databases. The case study of this paper is the Desaru beach in the eastern shore of Johor Bahru in Malaysia. In this investigation, Acoustics Toolbox of BELLHOP through MATLAB and mathematical analyzing method has been utilized. As a result, this paper indicates the maximum received power, and the lowest delay time characteristics and TL belong to horizontal point-to-point scenario; moreover, the ground-based scenario has the highest delay time and maximum coherence bandwidth among three scenarios. [ABSTRACT FROM PUBLISHER]

Remotely sensed sea-surface temperature (SST) retrievals with a significant positive bias during the occurrence of upwelling phenomena along the southeastern coast of Brazil were reported in our companion paper. As a result, this paper proposes an automated bias correction algorithm to improve the MODIS long-wave multichannel SST (MCSST) retrievals during the abovementioned conditions in this region. In this paper, MODIS daytime SST data (SSTMODIS) and differences between brightness temperatures in MODIS channels 31 and 32 (BT31 − BT32) are analyzed simultaneously with hourly wind surface conditions, in situ SST at 0.3 and 10 m in depth (SSTbuoy03 and SSTbuoy10), and sensible and latent heat fluxes from the Cabo Frio buoy data (at 23° S, 42° W) during 2014. The obtained results show that some upwelling events present air temperature ($T_{\mathrm {air}}$) greater than SSTbuoy03 and low-atmospheric water vapor content. A simultaneous occurrence of these factors during upwelling conditions may lead to a warm-skin layer effect and may cause BT31 to be greater than SSTbuoy03 and BT31 − BT32 to be small (−0.18 °C ± 0.22 °C), affecting the MCSST performance. The proposed bias correction algorithm uses a least-squares curve between SSTbuoy03 and SSTMODIS retrievals when BT31 − BT32 ≤ 0.5 °C (i.e., dry atmospheric conditions). The bias correction algorithm has significantly improved the SSTMODIS bias (RMSE) from 1.43 °C to −0.2 °C (1.60 °C to 0.58 °C) when applied to 22 cloud-free pixels of MODIS during January–March of 2015. [ABSTRACT FROM AUTHOR]

In this paper, the focus is on precipitation rate retrieval using 118.75 and 183.31-GHz channels from the microwave humidity and temperature sounder (MWHTS) onboard the FY-3C satellite. These channels provide not only atmospheric humidity profile measurements but they also provide temperature profile measurements. These measurements play important roles detecting and retrieving precipitation rates. Data from the MWHTS and the Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis (TMPA) 3B42 are matched in time and space. Matched datasets are used to verify precipitation detection algorithms and precipitation rate retrieval algorithms. To retrieve the precipitation rate, the multiple linear regression algorithm and back propagation (BP) neutral network algorithm are applied in the ten models proposed in this paper. After detailed retrieval analysis between these two algorithms, advanced algorithms are presented this paper to improve the accuracy of the precipitation rate retrieval. In our algorithms, the correlation coefficient of the precipitation rate over the ocean can reach 0.82, the bias is approximately 0.07 mm/hr, and the root mean square error (RMSe) is less than 0.4 mm/hr. Over land, the correlation coefficient is approximately 0.73, the bias is 0.1 mm/hr, and the RMSe is less than 0.5 mm/hr. These results show that our retrieval algorithms improve the retrieval accuracy. Moreover, we study a number of typhoons and find that the FY-3C MWHTS works well to retrieve typhoon precipitation rates. The potential sensitivities of the temperature and humidity channels are analyzed, which can improve the retrieval accuracy and lay the foundation for further research. [ABSTRACT FROM AUTHOR]

This paper discusses the intersatellite radiometric calibration for microwave sounders in support of NASA’s Global Precipitation Measurement (GPM) mission. This paper is an extension of previous GPM Intersatellite Calibration Working Group work, which assesses the robustness of the Central Florida Remote Sensing Laboratory “double difference” technique for sounders intercalibration. In this paper, we will analyze the intercalibration between the Advanced Technology Microwave Sounder on board the National Polar-orbiting Operational Environmental Satellite System Preparatory Project, the Microwave Humidity Sounder on board the MetOp-A and MetOp-B and NOAA-18 and NOAA-19, and the Sondeur Atmosphérique du Profil d’Humidité Intertropicale par Radiométrie sounder onboard the Megha-Tropiques satellite. The sensitivity of the calibration to the geophysical parameters and incidence angles is investigated using two years data. Here, it is observed that a reliable intercalibration can be made only when the path lengths of the two sensors are similar, so when matching the scan angles for the two sensors, the sensitivity of the biases upon the water vapor profiles is significantly reduced. [ABSTRACT FROM AUTHOR]

In recent years, many oil spill weathering process models have been developed to predict the trajectory and fate of oil at sea. As a part of oil spill damage assessment model, a precise prediction of physical fate and chemical properties of spilled oil on the sea surface is a key factor to assess environmental damages and take response actions. A system dynamic (SD) model is applied to predict the physical fate and properties of spilled oil in this paper, since oil weathering processes affect each other after spillage. The major oil weathering processes, spreading, evaporation, dispersion, emulsification, dissolution, biodegradation, and oil properties, dynamic viscosity, dynamic density, and oil–water interfacial tension, are included in the SD model and simulated later. The main purpose of this paper is to provide a new way to predict oil weathering processes and oil mass balance using the SD model. [ABSTRACT FROM AUTHOR]

The Visible Infrared Imaging Radiometer Suite (VIIRS) sensor aboard the NOAA-20 (previously JPSS-1) spacecraft has successfully operated since its launch in November, 2017. Similar to the first VIIRS instrument on the Suomi-National Polar-orbiting Partnership (SNPP) spacecraft, the data are collected in 22 spectral bands that are calibrated by a set of onboard calibrators. This paper provides an overview of the NOAA-20 VIIRS on-orbit operation and calibration, with a particular focus on the thermal emissive bands (TEBs). The results presented in this paper include the on-orbit changes in the TEB spectral band responses, detector noise characterization, and key calibration parameters, such as the nonlinear coefficients derived from the blackbody warm-up cool-down cycles. Other issues, such as the early mission long-wave infrared (LWIR) response degradation due to icing on the dewar window, and their impact on sensor calibration are also discussed. Since launch, the VIIRS instrument temperature has been stable to within ±0.8 K and the cold focal plane temperatures are well controlled with variations less than 40 mK. With the exception of the early degradation observed in the LWIR bands, the TEB gains have been stable to within 0.04% (except I5 at 0.07%). Based on the current performance, VIIRS is expected to meet its calibration requirements throughout its design lifetime. [ABSTRACT FROM AUTHOR]

This paper describes a new model of the seawater dielectric constant as a function of salinity and temperature at L-band. The model function is developed by fitting the accurate measurement data made at 1.413 GHz to a third-order polynomial. The purpose of this study is to provide an accurate model for earth-observing satellites to retrieve seawater salinities from remote sensing data. In this paper, the development of the model function is introduced along with an analysis of the goodness of fit. The model function is then compared with the model functions of Klein-Swift and Meissner-Wentz. Finally, the comparison is made between the retrieved salinity from the satellite data with the in situ data measured by Argo floats. [ABSTRACT FROM PUBLISHER]

Global warming represents a serious threat to human civilization. \textCO_2 emissions have been considered to be the main basis for the incredible increase in the earth's surface temperature in recent years. Most emissions result from human activities and are associated with the energy industry. Thus, developing an extensive framework of effective agents for managing this situation and the various relationships involved is important. Accordingly, this paper aims to provide a comprehensive system dynamics model, which is based on the systems thinking approach, to address the issue of global warming, in terms of households' energy consumption behaviors. The proposed model provides a broad overview of key agents affecting energy consumption, including government/public sector, households, and power industry. This model is verified by simulating different scenarios. [ABSTRACT FROM PUBLISHER]

Still largely untapped, wave energy may represent an important share in the energy mix of many countries in the future. However, the power fluctuations generated by most wave energy devices with little to no storage means, or without suitable control strategies, may cause power quality issues that must be solved before large wave energy farms are allowed to connect to a network. For instance, large power fluctuations may induce an excessive level of flicker in the distribution networks to which they are currently envisaged to be connected. Although storage appears to be a technically feasible solution, the minimum amount of storage required for a wave farm to become grid compliant with respect to typical flicker requirements is still unknown and is therefore investigated. This study constitutes the first part of this paper. Another issue, on which the second part of this paper focuses, concerns the optimal dimensioning of wave farm electrical components, which is traditionally performed assuming steady-state conditions (i.e., a constant current level), and is thus irrelevant in the case of wave farms outputting power fluctuations of significant amplitude. Hence, a second study, the results of which are presented in this paper, focuses on the minimum current rating for which a submarine cable may be safely operated without thermal overloading. Addressing both these issues is essential to the economic viability of a wave farm as the cost of both storage means and electrical components is highly dependent on their rating and may represent a significant percentage of the capital expenditure. [ABSTRACT FROM AUTHOR]

A long-term historical aerosol optical depth (AOD) data set from 1982 to 2011 over China (15–45° N; 75–135° E) with 0.1 spatial resolution has been produced from Advanced Very High Resolution Radiometer (AVHRR) Pathfinder Atmospheres—Extended level-2B data. The spatial distribution pattern shows that high AOD values are found in central and eastern China over the entire period with AODs larger in summer and spring than in autumn and winter. As the high-quality products from AERONET were absent for this period over mainland China, AOD data obtained using the broadband extinction method from solar radiation stations have been used to verify the quality of the AVHRR AOD data set over China. The intercomparison results show that the interannual variation of AOD has been well captured in the variation curve of the AOD monthly mean and the variation trend is also consistent over the whole period. The correlation coefficient of the monthly mean is mostly larger than 0.55, the agreement index is larger than 0.57, and the relative error is less than 21%. Both AVHRR and visibility data sets show high values in regions with rapid economic development. Using Moderate Resolution Imaging Spectroradiometer AOD data as references, it is found that AVHRR AOD from this paper has better accuracy in general than that from Deep Blue (DB) algorithm over China, especially over eastern and southern China, while DB provides more coverage especially over bright surface such as northwest China. This long-term historic AOD data set can be used together with other AOD data sets to study the climate and environmental changes, especially in the 1980s and 1990s. [ABSTRACT FROM AUTHOR]

The retrieval of land surface temperature (LST) from remote sensing techniques has been studied and validated during the past 40 years, leading to important improvements. Accurate LST values are currently obtained through measurements using medium resolution thermal infrared (TIR) sensors. However, the most recent review reports demonstrated that the future TIR LST products need to obtain reliable temperature values at a high spatial resolution (100 m or higher) to study temperature variations between different elements in a heterogeneous kilometric area. The launch of high-resolution TIR sensors in the near future requires studies of the temporal evolution and spatial heterogeneities of the elements in a mixed region. The present study analyzes the LST in a sub-kilometric highly heterogeneous area, combining the use of LST products from high-resolution TIR orbiting sensors with the LST maps created from a TIR camera onboard an unmanned aerial vehicle (UAV). The aim is to estimate the LST variability in a heterogeneous area containing different surfaces (roads, buildings, and grass), observed from different TIR sensors at different spatial resolutions, covering from the meter to the kilometer scales. Several results showed that variations in the LST up to 18 °C were identified with the UAV-TIR camera, and significant differences were also present in the LST products obtained from simultaneous overpasses of high-resolution satellite TIR sensors. A second objective of the study, due to the availability of the high-resolution LST fields, was to explore the thermal advection between different elements and determine if it correlates with the surface energy budget in the same area, thus indicating that this process is of importance for heterogeneous terrains at these scales. This paper also highlights the relevance of the UAV-TIR camera flight for future studies since it is not commonly used in TIR remote sensing but has substantial potential advantages. [ABSTRACT FROM AUTHOR]

The Moderate Resolution Imaging Spectroradiometer (MODIS) is a whisk broom scanning radiometer, which is onboard the Terra and Aqua spacecraft. Both MODIS instruments have successfully completed more than 12 years of on-orbit flight. The long-wave infrared (LWIR) photovoltaic bands (bands 27–30, 6.72–9.73 μm) on the LWIR focal plane assembly in Terra MODIS have contamination due to electronic crosstalk. In this paper, we examine Terra MODIS band 28 (7.33 μm) crosstalk effects, their impact, and mitigation. The crosstalk signal is identified and characterized using the regular lunar observations acquired by MODIS. It is evident from the derived crosstalk coefficients that the contamination was mainly from bands 27 (6.72 μm), 29 (8.55 μm), and 30 (9.73 μm). The crosstalk coefficients are generally a small positive quantity in the early to middle part of the mission with a few exceptions, and then changing directions. A linear correction algorithm is applied to both L1B calibration and retrieval to qualitatively and quantitatively assess the impact and improvements in this paper. It is shown that the crosstalk correction improved the imagery and radiometric fidelity of this band. [ABSTRACT FROM PUBLISHER]

The Bayesian hierarchical model has the outstanding capacity to combine prior knowledge with observations, as well as to generate rich spatiotemporal patterns. However, this advanced method has limited use in remotely sensed lattice data applications due to the large computational burden and unreasonable statistical inferences based on statistical units with a fixed scale. This paper presents a multiscale spatial homogeneous subdivision method and develops a Bayesian space–time hierarchical model (BSTHM) for remotely sensed lattice data. This can solve the above-mentioned limitations by constructing multiscale spatial homogeneous units with good statistical properties. The quantitative criteria for subdivision are provided. The outcome of the BSTHM is not only more reasonable in theory but also much easier to interpret; meanwhile, the computational efficiency is also considerably improved. This novel approach and its merits are illustrated by a case study that examines the spatiotemporal variation of PM2.5 pollution in Asia from 2000 to 2014 using remotely sensed data describing PM2.5 annual mean concentrations. Overall spatial pattern, common time trend, and local variation trend were decomposed and quantificationally estimated from an intricate spatiotemporal process. [ABSTRACT FROM AUTHOR]

Wireless sensor networks are widely used for environmental monitoring in remote areas. They are mainly composed of wireless sensor nodes, usually powered by batteries with limited capacity, but are expected to communicate in long range and operate for extended time periods. To overcome these limitations, many energy harvesting techniques are proposed to power wireless nodes for prolonged operation, whereas multihop techniques are utilized to extend the communication range. In this paper, a novel floating device with multisource energy harvesting technology that can be used as a wireless sensor node is proposed. The long range communication between wireless sensor nodes and a gateway is established through LoRa technology. In addition to conventional solar panels, an energy harvesting technique based on thermoelectric generators exploiting thermal differences created between water surface and materials exposed to sunlight is proposed. Energy generated from photovoltaic and thermoelectric generators is combined to power the wireless sensor node. This floating device consumes 6.6216 Wh per day when used as a wireless sensor node for the collection and transmission of environmental data. The sensor node can operate on a water surface for at least 9.6 days when it is not exposed to sunlight. During a sunny day, the floating device can harvest 8.375 Wh from solar panels and 0.425 Wh from thermoelectric generation. In other words, the floating device harvests sufficient energy to be self-sustaining during sunny days. [ABSTRACT FROM PUBLISHER]

This paper evaluates the calibration quality during the blackbody (BB) warm-up cool-down cycle for thermal emissive bands onboard Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) and Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS). This evaluation utilizes data from Aqua MODIS Collection 6 Level-1B products and VIIRS Sensor Data Records in 6-min granule format provided by the NASA Land Science Investigator-led Processing System. Nearly simultaneous hyperspectral measurements from the Aqua Atmospheric Infrared Sounder (AIRS) and the S-NPP Cross-track Infrared Sounder (CrIS) are used as references for MODIS and VIIRS, respectively. Each AIRS footprint of 13.5 km is co-located with multiple MODIS pixels while each CrIS field of view of 14 km is co-located with multiple VIIRS pixels. The corresponding AIRS-simulated MODIS and CrIS-simulated VIIRS radiances are derived by convolutions based on sensor-dependent relative spectral response functions. In this paper, the analysis mainly focuses on the bands that are used in sea surface temperature products. The results show that there is virtually no impact for MODIS bands 22 and 23 and bands 31 and 32 for a BB temperature below 290 K; however, when the BB temperature increases above 290 K, the impact is up to 0.3 K for bands 22 and 23 and 0.05 K for bands 31 and 32, respectively. For VIIRS, BB temperature-dependent drifts are observed in M15 and M16, which can reach 0.15 and 0.1 K, respectively, over the operational BB temperature range and the VIIRS brightness temperature range. [ABSTRACT FROM AUTHOR]

This paper analyzes the large positive bias of sea surface temperature (SST) retrievals of selected remotely sensed algorithms recorded during the simultaneous occurrence of upwelling and atmospheric subsidence along the coastal waters of Rio de Janeiro, Brazil. The optimal estimator (OE) for retrieving SST and the multichannel (MCSST) and nonlinear (NLSST) estimators are compared using Advanced Very High Resolution Radiometer-3 data. The in situ SST (SSTbuoy) data set used to validate the remotely sensed SST retrievals was collected from five moored buoys (four in the open sea and one in coastal waters). The principal results of this paper are as follows. First, the sensitivity analyses show that OE is quite susceptible to the first-guess SST rather than to the humidity profiles. Second, the comparison between the SSTOE and 365 cloud-free SSTbuoy measurements in open sea waters presents an root mean squared error (RMSE), bias, and standard deviation (STD) with the intervals of [0.5, 0.6], [−0.51, 0.13], and [0.27, 0.48], respectively. Third, the MCSST, NLSST, and OE SST produce a positive bias that can reach 5 K during simultaneous upwelling and atmospheric subsidence in coastal waters. Such unexpected errors are due to low SST values and water vapor compression in the lower layer of the atmosphere related to a temperature inversion. Fourth, an alternative approach using SSTbuoy obtained on the previous day as a first guess instead of the climatological SST significantly improves the errors (SSTOE–SSTbuoy) by reducing RMSE, bias, and STD by 58% (from 3.30 to 1.39 K), 73% (from 3.00 to 0.80 K), and 19% (from 1.38 to 1.12 K), respectively. [ABSTRACT FROM PUBLISHER]

Satellite remotely sensed products provide critical information to weather forecasters at the National Oceanic and Atmospheric Administration (NOAA) and greatly supplement spare or nonexistent surface observations. Low earth orbiting passive microwave sensors provide unique information related to atmospheric moisture and precipitation, as well as surface properties such as oceanic wind speed. This paper will focus on two microwave sensors that are part of NOAA's Joint Polar Satellite System—the Advanced Microwave Scanning Radiometer 2 (AMSR2) and the Advanced Technology Microwave Sounder (ATMS)—which are flown on Japan's Global Change Observation Mission—Water (GCOM-W1) and the Suomi National Polar orbiting Partnership (S-NPP) satellites. The orbits of GCOM-W1 and S-NPP are such that AMSR2 and ATMS observe the same region of the earth nearly the same time of the day. This allows for comparison of similar products from the two sensors, which is of great interest to users such as NOAA's National Weather Service. In this paper, we focus on product comparisons for a historic flooding event in the U.S. associated with Hurricane Joaquin. The microwave products are presented and shown with other widely used in-situ observations. The performance of AMSR2 and ATMS products are compared. The higher spatial resolution of the AMSR2 sensor provides more detailed information on water vapor and rain rate compared to ATMS. On the other hand, the wider swath width of the ATMS provides a more continuous field of water vapor and precipitation, as well as water vapor retrievals over land. [ABSTRACT FROM PUBLISHER]

This paper investigates the physical-layer security for water-to-air (W2A) visible light communication (VLC). The impacts of surface fluctuation and underwater scattering on the channel gain are theoretically analyzed, which is verified in a laboratory W2A-VLC link. The statistical properties of wave slope under experimental conditions are measured by image processing and the probability density function of the slope can be approximated by a logistic distribution. We observe that dynamic waves can cause information leakage and experimental results indicate that the probability of secure communication increases from 90.39% to 96.18% as the eavesdropper’s elevation increases from 1.15 m to 1.42 m, which are approximately consistent with the numerical results. To investigate the parameters affecting the secrecy performance, several secrecy performance metrics are numerically calculated under different wave intensities, eavesdropper’s locations, divergence angles of LED, underwater scattering coefficients and wavelengths of transmitted beam. It is seen that the secrecy performance is degraded as the wave intensity increases, while random scattering can mitigate the water surface fluctuations and reduce the probability of information leakage. [ABSTRACT FROM AUTHOR]

This paper presents a framework for using remote sensing imagery and image processing techniques to analyze the interactions among tropical depressions (TDs) and typhoons. The purpose is to properly understand and predict this phenomenon, in order to reduce their influence on the regions where they pass by. Improvements on the understanding of the interactions among TDs and typhoons are obtained and presented. They carry the potential to improve forecast of severe weather system. In this paper, we analyzed the physical responses of TDs on two typhoons Tembin and Bolaven (2012), including TD's appearance, development, interaction, and mergence. According to the Central Weather Bureau of Taiwan, Tembin and Bolaven were formed about 1550 km apart. In general, the Fujiwhara effect happens when two storms are within a distance of 1400 km. Does the TD have impacts on the typhoons, and could we also call this impact as Fujiwhara effect? The 3-D profiles of the weather systems are reconstructed using the multifunctional transport satellite (MTSAT) infrared cloud images by the image reconstruction technique (IRT). The 3-D profiles of typhoons were implemented for investigating the in-depth distribution of the cloud top from a surface cloud image. The main parameters, which have been analyzed in this paper, are distance, height difference, rotation, and sizes of the two TDs and the two typhoons. The results showed that two TDs occurred between typhoons Tembin and Bolaven, which interacted with each other through upward convection and attraction between two typhoons and the TDs, respectively. The mergence of the two TDs caused the typhoons to start rotating and generate strengthened power. The findings of the TD effects on two typhoons represent a new aspect of the interaction between TD and typhoon. [ABSTRACT FROM PUBLISHER]

This technical communication describes a method to size the drop weights used by submersibles for diving and surfacing taking into account varying seawater density profiles. The method allows consistent diving and surfacing performance to be achieved for differently sized submersible and target dive depths. The conditions that need to be met for safe operation of a submersible are described in this paper. The equations needed to appropriately ballast a platform and size its diving and surfacing drop weights are derived, highlighting some inherent limitations of using a two drop weight method for certain types of mission. The performance of the proposed approach is demonstrated through numerical simulations for different sized submersibles and target depths. The results show the effects of using different design parameters to illustrate some useful patterns and trends that can assist submersible developers and operators predict the effects of environmental and design uncertainties on important operational parameters such as the time taken for diving and surfacing. [ABSTRACT FROM AUTHOR]

The radiometric stability of selected thermal emissive bands (TEBs) of the Moderate-Resolution Imaging Spectroradiometer (MODIS) on the Terra and Aqua satellites is examined via a direct intersensor comparison with the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (SNPP) satellite. The analysis adapts a “nadir-only” refinement of the simultaneous nadir overpasses (SNOs) analysis to evaluate radiometric deviations in MODIS Collection 6.0 and 6.1 data releases, the latter having been implemented with a version of crosstalk effect mitigation for Terra MODIS bands 27–30. The comparison time series result, with an average precision of 0.4%, shows radiometric deviation in Terra MODIS band 29 ($8.55~\mu \text{m}$) up to 6%, or 3 K in brightness temperature (BT), in Collection 6.0, and correspondingly −1.5%, or −0.7 K in BT, in Collection 6.1, in particular significantly worsened by the safe mode event of February 2016. This paper includes the inter-TEB comparisons of MODIS bands B31 and B32 with SNPP VIIRS as two representative cases of nonideal spectral match demonstrating various key features and new information as revealed under the “nadir-only” framework, and also describes a procedure using both radiance-to-radiance comparison and BT-difference time series to estimate the BT-difference uncertainty specifications as well as the radiance-to-radiance time series baselines that are shifted away from unity. The finding for Terra MODIS band 29 highlights the continual nontrivial impact of crosstalk effect on numerous TEBs of MODIS Collection 6.1 not fully mitigated, which can further impact cloud masks, sea surface temperatures, and other product retrievals. [ABSTRACT FROM AUTHOR]

Cooperative transmission is a promising solution for reliable communication in underwater acoustic sensor networks. To fully exploit the benefits of cooperative system, efficient management of relay resources is required. However, the challenging working conditions, including imprecise channel information, limited observation feedback and dynamic underwater environment, call for an adaptive relay selection strategy for improving system capacity performance. In this paper, we present an innovative Partial Expert-based Reinforcement Adversarial Learning (PER-AL) strategy that unifies expert assisted learning and self-adjusting learning in a integral adversarial multi-armed bandit framework. The user constantly interacts with the environment and optimizes the relay decision by analyzing all gathered observation rewards, rather than relying on prior channel information. By introducing a novel expert learning mechanism into the initial learning stage, expert generator and expert learner are proposed to control the performance of experts and provide optimal expert advice to reinforce the initial relay learning for efficiency. With the deepening learning, the relay quality is then evaluated by analyzing the historical observable rewards directly through a Exp3 policy without engaging complexity too much. The proposed algorithm could automatically adapt to the underwater conditions and detect the optimal relay within a short time, significantly improving system capacity without jeopardizing the adversarial regret guarantee. Finally, extensive simulation results demonstrated the superior of PER-AL algorithm compared with recent existing CSI-based and CSI-free solution benchmarks. Particularly, PER-AL algorithm has a 28.3% improvement of the total network capacity and achieves a 44.5% decrease of implementation time. [ABSTRACT FROM AUTHOR]

A theoretical understanding of a multifrequency microwave approach to understand complex microwave interactions from a highly saline snow cover on a relatively smooth first-year sea ice is presented. We examine the sensitivity of Ku-, X-, and C-band \sigma {\text {VV}}^{0} and \sigma {\text {HH}}^{0} to variability in snow geophysical properties such as salinity, density, temperature, and snow grain radius, sampled from a highly saline snow cover on first-year sea ice. A first-order multilayer snow and ice backscatter model is used to calculate \sigma {\text {VV}}^{0} and \sigma {\text {HH}}^{0} by taking into account the surface and volume scattering contributions within each snow layer of the snow pack. Penetration depth models are used to calculate the potential penetration of all three frequencies, at initial and perturbed snow property conditions. Sensitivity analyses suggest that variability in salinity and snow grain radius have the greatest effect, followed by density and temperature. This phenomenon is observed for all three frequencies, influencing microwave penetration and backscatter. Dielectric loss associated with highly saline snow covers and substantial changes in scattering contributions from snow grain radius perturbations were found to be the dominant factors affecting microwave penetration and backscatter. Results from this paper demonstrate the potential of using a multifrequency theoretical approach to correlate with active microwave observations to determine the geophysical and electrical state of snow/sea ice system. The paper also represents an evolution in a theoretical understanding on how an active microwave approach using multiple frequencies can be further utilized toward the development of snow thickness and/or snow water equivalent algorithm on smooth FYI. [ABSTRACT FROM PUBLISHER]

In this paper, the surface emissivity is retrieved over the Arctic sea ice/open seas using observations from the advanced microwave sounding unit window channels during the year 2009. The emissivity computation is performed using two contrasted surface assumptions: specular and Lambertian assumptions. The obtained sea ice surface emissivities are studied in this paper with a focus on the effect of the surface assumption. Some factors of variability of the obtained emissivities are analyzed: variability in space, in time, with the zenith angle, and with respect to the frequency. We show that the near-nadir surface emissivity and emissivity difference (obtained using two contrasted surface assumptions) could be used as an excellent proxy to detect ice/no ice regions. We also show that near-nadir sea ice emissivity at some selected frequencies and the combination of both high and low window frequencies could also be very useful to better characterize sea ice surface physical properties and provide additional information for existing sea ice classifications, as they bring relevant information about first year and multiyear sea ice properties and their seasonal evolution. [ABSTRACT FROM AUTHOR]

Oil and gas production facility installations in the North Slope of Alaska require a high degree of modularization. This paper will present a modularization concept for a large gas treatment plant intended for installation on the North Slope. This paper discusses design trends and techniques used in the optimization and integration of the electrical design, and the use of 3-D modeling to expedite the design, coordination, and assembly at the fabrication yard and at site. [ABSTRACT FROM AUTHOR]

The global measurement of sea-surface salinity and more precise measurements of soil moisture from space has been enabled by L-band observations from the Soil Moisture and Ocean Salinity (SMOS) mission, the Aquarius mission, and the Soil Moisture Active Passive (SMAP) mission. These measurements are key components of the global water cycle and the ability to resolve climate scale variations in these variables is extremely valuable for improved understanding of how the hydrologic cycle varies in a changing climate system. It is therefore imperative that the radiometer systems making these measurements be calibrated to remove any spurious instrument temporal drifts. In this paper, models are developed over Antarctica and rainforest regions to track the gain and offset drifts in spaceborne L-band radiometer brightness-temperature (TB) measurements. The Antarctica region is found to be best for tracking small variations (0.1 K over 10 days) for vertically polarized observations near the Brewster angle. The rainforest regions are found to be best for tracking longer term variations ($ > $60 days) in all channels, due to larger uncertainty in the surface temperature knowledge, and excellent for tracking shorter term variations between channels ($ < $10 days). These reference regions were used to separate a long-term gain drift and a quasi-monthly offset variation in the Aquarius radiometer. These observations eventually led to the characterization of the root cause for the drift and are contributing to improved correction methods based on models for the hardware behavior. [ABSTRACT FROM PUBLISHER]

In this paper, we evaluate the near-surface air temperature datasets from the ERA-Interim (ERAI), Japanese 55-Year Reanalysis, Modern-Era Retrospective Analysis for Research and Applications Version 2, NCEP1, and NCEP2 reanalysis projects. Reanalysis data were first compared to observations from weather stations located on wheat areas of the United States and Ukraine, and then evaluated in the context of a winter wheat yield forecast model. Results from the comparison with weather station data showed that all datasets performed well (r2 > 0.95) and that more modern reanalysis, such as ERAI, had lower errors [root-mean-square difference (RMSD) ∼0.9 °C than the older, lower resolution datasets, such as NCEP1 (RMSD ∼2.4 °C). We also analyze the impact of using surface air temperature data from different reanalysis products on the estimations made by a winter wheat yield forecast model. The forecast model uses information of the accumulated growing degree day (GDD) during the growing season to estimate the peak normalized difference vegetation index signal. When the temperature data from the different reanalysis projects were used in the yield model to compute the accumulated GDD and forecast the winter wheat yield, the results showed smaller variations between obtained values, with differences in yield forecast error of around 2% in the most extreme case. These results suggest that the impact of temperature discrepancies between datasets in the yield forecast model get diminished as the values are accumulated through the growing season. [ABSTRACT FROM AUTHOR]

In this paper, a time series of 33 TerraSAR-X copolarized synthetic aperture radar (SAR) imagery collected in Stripmap mode over the Gulf of Mexico in a wide range of incidence angles and sea-state condition is exploited, together with a theoretical framework based on the X-Bragg scattering model, to analyze the effects of noise, angle of incidence, (AOI) and wind speed on the standard deviation of the copolarized phase difference ($\sigma _{\phi _{c}}$) evaluated over sea surface with and without oil slicks. This large data set represents an unprecedented opportunity to analyze, for the first time, the influence of both SAR acquisition and surface parameters on the broadening of the copolarized phase difference probability density function (pdf), $p_{\phi _{c}}(\phi _{c})$. Experimental results show that the X-Bragg scattering model, here adopted to predict the sea surface $p_{\phi _{c}}(\phi _{c})$ , gives an understanding of the increasing trend of $\sigma _{\phi _{c}}$ with respect to AOI. It is shown that the noise significantly contributes to broaden $p_{\phi _{c}}(\phi _{c})$ over both slick-free and slick-covered sea surface, while the effects of low-to-moderate wind regimes are negligible. In addition, $\sigma _{\phi _{c}}$ exhibits a larger sensitivity to the scene variability, if compared to single-polarization intensity channels, over both slick-free and oil-covered sea surface. This sensitivity is more pronounced at lower AOIs due to the higher noise equivalent sigma zero (NESZ) that affects larger AOIs. [ABSTRACT FROM AUTHOR]

The Suomi National Polar-orbiting Partnership Program Visible Infrared Imaging Radiometer Suite (VIIRS) thermal emissive bands (TEB) have been performing well during nominal operations since launch. However, small but persistent calibration anomalies are observed in all TEBs during the quarterly blackbody (BB) warm-up/cool-down (WUCD) events. As a result, the time series of daytime sea surface temperature (SST) (derived from bands M15–M16) show warm spikes on the order of 0.25 K. This paper suggests that VIIRS TEB WUCD biases are band dependent, with daily-averaged biases about −0.04 and 0.05 K for I4 and I5, and −0.05, −0.05, 0.11, 0.09, and 0.05 K for M12–M16, respectively. Two correction methods—Ltrace and WUCD-C—have been implemented and evaluated using colocated observations from the Cross-track Infrared Sounder (CrIS), radiative transfer simulations, and SST retrievals. Also an error in the National Oceanic and Atmospheric Administration operational processing was identified and fixed. Both correction methods effectively minimize WUCD-induced SST anomalies. The Ltrace method works well for I5, M12, and M14–M16, with residual biases about 0.01 K. The WUCD-C method, on the other hand, performs well to correct WUCD biases in all TEBs, with residual biases also about 0.01 K. However, it introduces warm biases relative to CrIS at cold scene temperatures, which requires further study. Applying nonequal BB thermistor weights improves calibration at BB temperature set points, but its impact on daily-averaged WUCD biases is small. The proposed methodologies may also be applied to the VIIRS onboard the follow-on Joint Polar Satellite System satellites. [ABSTRACT FROM AUTHOR]

An X-band vertical array system is developed for measuring and characterizing electromagnetic (EM) propagation in the marine atmospheric boundary layer. In particular, the evaporation duct that commonly forms over water is investigated as part of the Coupled Air-Sea Processes and Electromagnetic ducting Research (CASPER) at-sea experimental campaign conducted off the coast of Duck, NC, USA, during October–November of 2015. Monte Carlo simulations are first used to develop an optimal array of four vertically spaced receiving antennas. In the experiment, the antennas are mounted on the stern A-frame of a research vessel and measure EM signals transmitted from beacons mounted on another research vessel and on the pier at the Army Field Research Facility. While the propagation loss versus range provides a data set similar to previous work, the vertical array can provide sampling of modes in the leaky waveguide formed in the duct. Combining both the range and height sampling results in a robust inversion method for evaporation duct estimation. In this paper, the efficacy of the four-element array is demonstrated by estimation of the evaporation duct height through comparison with a library of precomputed propagation curves generated using the parabolic wave equation. Low model error gives confidence in the estimates, which are consistent with the concurrent environmental measurements performed by the CASPER team. It is found that the evaporation duct can vary significantly with range and time over the duration of a data collection run. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive procedure to improve the wind geophysical model function (GMF) for the Global Navigation Satellite System Reflectometry (GNSS-R) instrument onboard the TechDemoSat-1 satellite. The observable used to define the GMF is extracted from the measured delay-Doppler maps (DDMs) by correcting for the nongeophysical effects within the measurements. Besides the instrument and the geometric effects as provided in the bistatic radar equation, a calibration term that accounts for the uncalibrated receiver antenna gain and the unknown transmitter antenna gain is proposed to optimize the calculation of GNSS-R observables. Such calibration term is presented as a function of observing elevation and azimuth angles and is shown to remarkably reduce the measurement uncertainties. First, an empirical wind-only GMF is developed using the collocated Advanced Scatterometer (ASCAT) winds and European Centre for Medium-Range Weather Forecasts (ECMWF) model wind output. This empirical GMF agrees well with the model output. Then, the sensitivity of the observable to waves is analyzed using the collocated ECMWF wave parameters. The results show that it is difficult to include mean square slope (MSS) in the development of an empirical GMF, since the difference between ECMWF MSS and the MSS sensed by GNSS-R varies with incidence angle and wind speed. However, it is relevant to take significant wave height ($H_{s}$) in account, particularly for low wind conditions. Consequently, a wind/ $H_{s}$ approach is proposed for improved wind retrievals. [ABSTRACT FROM AUTHOR]

This paper proposes a different thermal channel combination split-window (DTCC-SW) method to estimate the land surface temperature (LST) and sea ST (SST) from the Chinese Gaofen-5 (GF-5) satellite thermal infrared (TIR) data. A nonlinear combination of two adjacent channels CH8.20(centered at $8.20~\mu \text{m}$) and CH8.63 (centered at $8.63~\mu \text{m}$) was proposed to estimate LST for low-emissivity surfaces. A nonlinear combination of two adjacent channels, CH10.80 (centered at $10.80~\mu \text{m}$) and CH11.95 (centered at $11.92~\mu \text{m}$), was developed to estimate LST and SST for high-emissivity surfaces under dry atmospheric conditions, and a nonlinear combination of two channels, CH8.63 and CH11.95, was used to estimate LST and SST for high-emissivity surfaces under wet atmospheric conditions. The numerical values of the DTCC-SW coefficients were obtained using a statistical regression method from synthetic data simulated with an accurate atmospheric radiative transfer model moderate spectral resolution atmospheric transmittance mode 5 over a wide range of atmospheric and surface conditions. The LST (SST), mean emissivity, and atmospheric water vapor content were divided into several tractable subranges to improve the fitting accuracy. The experimental results and the preliminary evaluation results showed that the root-mean-square error between the actual and estimated LSTs (SSTs) is less than 0.7 K (0.3 K), provided that the land surface emissivities are known, which indicates that the proposed DTCC-SW method can accurately estimate the LST and SST from the GF-5 TIR data. [ABSTRACT FROM AUTHOR]

The light-water one-rod equipment for loss-of-coolant accident (LOCA) experimental investigation (LORELEI) device, one of the experiments of the future experimental nuclear reactor Jules Horowitz of Commissariat à l’Energie Atomique et aux Energies Alternatives, will be dedicated to the study of the LOCA. For a better understanding of the temperature conditions during a LOCA, the surface temperature of the fuel cladding has to be monitored. For this purpose, we are designing a noncontact temperature measurement device based on multispectral pyrometry, adapted to the extreme conditions of LORELEI. In this paper, we present a radiative transfer model, taking into account the direct flux from the measured surface and contributions from the surroundings, to simulate the impact of high-temperature surroundings on the temperature estimated using the multispectral radiation thermometry (MRT) method. The hypothesis of a constant emissivity profile in the spectral ranges of calculation is used to estimate the surface temperature. Experimental pyrometry measurements are performed on Zircaloy-4 and Inconel surfaces in high-temperature surroundings to validate the model. As in LORELEI, an optical fiber is used to carry the infrared thermal flux from the cladding to the spectrometer. Thermocouples are used to give a reference temperature and to provide a complete temperature monitoring of the device. A temperature difference is observed between the “true” cladding temperature and the MRT temperature estimation, when the temperature of the surroundings is between 50 °C and 150 °C below the cladding temperature, and this difference increases with the cladding temperature. This provides a correction value to apply on the temperature estimation to approach the real cladding temperature. [ABSTRACT FROM AUTHOR]

Boron-doped carbon nanotubes (B-doped NTs) are predicted to behave as semiconductors over a large range of diameters and chiralities and might thus constitute a suitable class of materials for nanoelectronics technology; they could be used, for example, to enhance properties of supercapacitors as capacitance and time of charge/discharge. In this paper, we propose an electric arc to synthesize B-doped NTs, based on the erosion of graphite electrodes with nickel and yttrium as catalysts and boron as the doping element. This technique allows obtaining carbon nanotubes (NTs) doped with around 8% of boron, in a short amount of time (2 min) and under relatively low applied power (2 kW). B-doped NTs were characterized with scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Physical properties of the plasma were also studied using optical emission spectroscopy. Temperatures of around 5000 K were obtained suggesting a high concentration of $C_{2}$ molecules and then, the ideal conditions to synthesize NTs. [ABSTRACT FROM AUTHOR]

This paper discusses rating calculations of underground power cables when the temperature limit is imposed on a location other than the cable conductor. The issue becomes important for installations where the environmental conditions do not allow excessive heating. An example can be a requirement that the cable surface temperature is such that the drying out of the surrounding soil is avoided. Another example is a requirement imposed on submarine cable installations when the temperature rise caused by cable heating at the specified depth below the sea bottom does not exceed 2 K. Such requirements form rating restrictions in several countries; for example, the Netherlands, Germany, France, and others. This paper proposes new solutions to such problems including calculation of the dynamic ratings. [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the performance of a mixed radio-frequency-underwater wireless optical communication (RF-UWOC) system where an unmanned aerial vehicle (UAV), as a low-altitude mobile aerial base station, transmits information to an autonomous underwater vehicle (AUV) through a fixed-gain amplify-and-forward (AF) or decode-and-forward (DF) relay. The analysis accounts for the main factors that affect the system performance, such as the UAV height, air bubbles, temperature gradient, water salinity variations, detection techniques, and pointing errors. Employing the fixed-gain AF and DF relays, expressions for some key performance metrics are derived, e.g., outage probability (OP), average bit error rate (ABER), and average channel capacity. Moreover, in order to get further insights, asymptotic analyses for the OP and ABER are also carried out. Additionally, for the two relaying systems, we derive analytical expressions for the optimal UAV altitude that minimizes the OP. Simulation results show that the UAV altitude influences the system performance and there is an optimal altitude which ensures a minimum OP. Furthermore, it is demonstrated that the diversity order of the fixed-gain AF relaying depends on the RF link and pointing errors, while the diversity order of the DF relaying depends on the detection techniques and pointing errors. [ABSTRACT FROM AUTHOR]

In this paper, the well-known Ament model is generalized to multiple rebounds (reflections) from rough sea surfaces in a stratified medium. To solve this propagation-scattering problem in the radar microwave domain, the physical optics (PO) approximation is applied to determine the currents on the rough sea surface. Next, to solve the propagation problem, i.e., to calculate the scattered field in the duct, an appropriate Green function of the duct (which is a stratified medium with linear-square refraction index profile) is used to radiate the currents from Huygens’ principle. Due to refraction phenomenon, this field induces new currents on the surface (second rebound), which are again evaluated by PO. The process is iterated. Then, for each rebound, the coherent components of the surface currents and the scattered field are calculated and compared with those of a flat surface in order to derive the generalized Ament model. In addition, this model is compared with the results computed by the rigorous method of moments and accelerated by the multilevel subdomain decomposition iterative method combined with the adaptive cross approximation. [ABSTRACT FROM AUTHOR]

The seasonal cycle of landscape freeze/thaw (FT) state across mid- to high latitudes influences critical processes such as the land surface energy balance, carbon cycle dynamics related to vegetation growth, and hydrological partitioning between surface runoff and infiltration. In this paper, we produce the first daily FT classification for the 2011–2014 period based on L-band radar measurements from Aquarius. The radar FT algorithm used in this paper is based on a seasonal threshold approach, which is also the baseline algorithm applied to higher-resolution (3 km) radar measurements from NASA’s Soil Moisture Active/Passive (SMAP) mission (Launched January 31, 2015). The lower frequency (L-band) radar backscatter measurements from Aquarius provide enhanced sensitivity to FT conditions in vegetation canopy, snow and surface soil layers, although the relative radar penetration depth and sensitivity of the FT signal to these landscape elements will vary according to surface moisture and vegetation biomass conditions, and underlying land cover and terrain heterogeneity [1], [2]. Evaluation of the seasonal threshold FT algorithm using Aquarius was performed using surface air and soil temperatures from selected stations in the Snow Telemetry (SnoTel) network. Analysis identified good agreement during the fall freeze-up period with flag agreement exceeding the 80% SMAP accuracy target when summarized on a monthly basis. Disagreement was greater during the spring thaw transition due in part to uncertainty in characterizing thaw from in situ measurements. Unlike the fall season, stronger agreement in the spring was identified when the reference state was characterized with air temperature compared to soil temperature. [ABSTRACT FROM PUBLISHER]

The objective of this paper is to continue exploring the use of International GNSS Service (IGS) products as a tool to be used in Earth-space propagation experiments. With this purpose, 4 years of Zenith Tropospheric Delay data from IGS Villafranca station, in Madrid, Spain, have been processed with the aim to estimate the attenuation due to gases. These values are then used for the validation of a concurrent database of 4 years of radiometric measurements at 19.7 GHz, collected at Universidad Politécnica de Madrid (UPM) with the purpose of studying the attenuation effects of gases and clouds. The suggested validation procedure includes both an automatic routine and visual inspection. The validated measurements are statistically analyzed on a yearly and seasonal basis. Results point toward the usefulness of IGS data in propagation experiments as well as their integration in their processing routines. [ABSTRACT FROM AUTHOR]

Aquarius (AQ)/SAC-D is a joint National Aeronautics and Space Administration (NASA)/Comisión Nacional de Actividades Espaciales (CONAE; Argentine Space Agency) Earth Sciences satellite mission to measure global sea surface salinity (SSS), using a L-band radiometer/scatterometer that measures ocean brightness temperature (Tb) and radar backscatter (sigma-0). The application of L-band radiometry to retrieve SSS is a difficult task; therefore, precise Tb corrections are necessary to obtain accurate measurements. One of the major error sources is the effect of ocean roughness that “warms” the ocean Tb. The baseline approach, to provide this ocean roughness correction, uses the AQ radar scatterometer measurement of ocean sigma-0 to infer the radiometric excess ocean emissivity. In contrast, this paper develops an alternate approach for the AQ ocean roughness correction using the MicroWave Radiometer (MWR) Tb measurements at Ka-band. The theoretical basis of this MWR ocean roughness correction algorithm is described, which translates these Ka-band measurements to L-band to remove the AQ Tb errors that are caused by ocean wind speed and direction. MWR ocean roughness correction results are compared with corresponding results from the AQ scatterometer method. Also, AQ SSS retrievals are presented using both sets of roughness corrections that demonstrate the relative effectiveness of the MWR and AQ scatterometer approaches. [ABSTRACT FROM PUBLISHER]

In this paper, we compare satellite-borne Cand X-band synthetic aperture radar (SAR) data for marine oil spill observation. During large-scale oil-on-water exercises in the North Sea, quad-polarization Radarsat-2 (C-band) and dual-polarization TerraSAR-X (X-band) data were acquired with temporal distances of less than 24 min. The objective is to characterize and quantify differences in the Radarsat-2 and TerraSAR-X measurements. Three scene pairs are compared in terms of data quality and signal characteristics, including statistical properties and selected multipolarization (HH, VV) parameters. The signal characteristics are also compared among low-backscatter features of various origin within the individual pairs. No viable argument for selecting one sensor above the other is identified in the data quality study. In the statistical analysis, investigation of logcumulants indicates a larger deviation from Gaussian statistics in the TerraSAR-X data compared with Radarsat-2 measurements. Log-cumulant diagrams are also shown to be a useful tool for discrimination between oil spills and a simulated biogenic slick in both sensors. Multipolarization features show enhanced slick-sea contrasts and a better discrimination between mineral oil spills and other low-backscatter features in Radarsat-2 compared with TerraSAR-X. The presence of a non-Bragg scattering component in the data is revealed for both sensors. The relative contribution of non-Bragg scattering to the total backscatter is found to be higher in the TerraSAR-X data than in the Radarsat-2 data. In general, the non-Bragg component is found to account for a larger part of the backscatter in slick-covered areas compared with clean sea. [ABSTRACT FROM PUBLISHER]

This paper considers methods to classify and discriminate the multidimensional cyclostationary climatological time series. The methods take into account both the seasonal mean cycles and random behavior in the series, simultaneously considering means and all component-by-component autocovariances. This improves classical Hotelling T^2 statistics that classify through mean changes only, and constant-mean speech methods that classify exclusively through sample autocovariance differences. Here, two series are compared by assuming that both follow the same time series model; from this, a test statistic representing a distance between the two series is developed from linear prediction theory. This construction generates a level-\alpha test statistic for Gaussian data that can be used to assess how different the two series are. The derived distances can be used in a clustering algorithm, e.g., to group series with similar behavior. Such information is useful to eliminate or merge the climate stations whose data are redundant to another station or to optimally locate a collection of stations. The techniques are first tested on simulated series with known structures, and then applied to 11 two-dimensional series in the National Oceanic and Atmospheric Administration’s data buoy catalog. Natural clusters emerge which are geographically realistic. Specifically, the methods were able to perfectly group stations in the Gulf of Mexico, the Carolina Coast, the Pacific Ocean, and offshore New England. [ABSTRACT FROM PUBLISHER]

This paper describes the technical approach to generate homogeneous warm brightness temperature scene binary mask over the earth for the intercalibration of microwave imagers. The objective is to identify homogeneous desert scenes as targets in radiometric intercalibration of multisource multisensor systems such as Global Precipitation Measurement (GPM) constellation. In this paper, a method is developed to generate mask over continental Australia using 10, 18, and 37 GHz vertical and horizontal polarized radiance observations from GPM Microwave Imager data. Major factors considered are diurnal variation, second Stokes parameter, spatial homogeneity, and surface emissivity. Major advantage of this tool is its minimal, almost negligible, dependence on any external ancillary modeled or observed data. [ABSTRACT FROM AUTHOR]

This paper extends a former study on super-typhoon’s formation in winter to its seasonal dependence on distribution and profiles. It aims to enhance understanding and predictability of the super-typhoons to reduce their impacts on human beings and properties in the regions where they pass by or influence. A framework by integrating remote-sensing imagery and image-processing techniques is implemented to analyze the seven super-typhoons of concern in both summer and winter seasons in the northwestern Pacific Ocean. Conventionally, typhoons occur in summer in the Northern Hemisphere, while owing to increased climate variability in recent decades, the occurrence of typhoons in winter is increased and a large number of super-typhoons are observed. Surprisingly, three summer super-typhoons—Neoguri (July), Rammasun (July), and Halong (August)—and four winter super-typhoons—Phanfone (October), Vongfong (October), Nuri (November), and Hagupit (December)—happened in 2014. Their physical responses of tracks, distributions, profiles, and intensifications are examined. The 3-D profiles of typhoons derived from surface cloud images are used to investigate the in-depth distributions of the cloud tops. Results show that southwest airflows, and cold fronts and southwest airflows enhance the summer and winter typhoons, respectively, to become super-typhoons eventually within the zones of lat 15°–20° and 10°–20°N and long 110°–135° and 133°–138°E in summer and winter, respectively. The lat 20°N is likely the boundary for the super-typhoons’ occurrence and a turning point of the typhoons’ two major tracks, with the first track moving in the westerly direction and the second track inclining in the northerly direction. Three crucial findings are obtained. First of all, it is observed that Track 1 inclined toward the latitude with an inclination angle $\theta _{1}$ and Track 2 inclined toward Track 1 with an inclination angle $\theta _{2}$. Using both inclination angles, the patterns of the super-typhoons were approximately described. Second, the inclination angle $\theta _{1}$ of the winter super-typhoons is represented with smaller values and a narrower range (10°–26°) than those (13°–40°) of the summer super-typhoons. After the turning point, both inclination angles $\theta _{2}$ of winter and summer super-typhoons varied with a wider range of 25°–65° and −35° to 50°, respectively. The winter super-typhoons exhibit higher intensities than the summer super-typhoons. Third, it is further confirmed that a mechanism through which cold fronts and southwest airflows enhance the typhoons causes them to become super-typhoons. The cold front is a new aspect of the leading edge of cooler air masses in typhoon environments exerting a greater temperature gradient between the front and typhoon circulation that ultimately affects the track of typhoons and increases the intensity of typhoons. [ABSTRACT FROM AUTHOR]

The aim of this paper was to propose a new methodology for preprocessing and enhancing C-band synthetic aperture radar (SAR) images for the automatic detection of marine oil slicks. The proposed methodology includes three processing levels: preprocessing, thresholding, and binary cleaning. The first level is to correct the heterogeneity of brightness in SAR images caused by the non-Lambertian reflection of the radar signal on the sea surface. This heterogeneity can be justified by: the distance from the nadir (incidence angle effect), the interaction between wind direction and radar pulse, and the wide swath mode. The second level consists of a thresholding step. The third level is to clean the binary output images from noise residues. Several preprocessing and cleaning methods have been tested and evaluated by a qualification engine that compares the automatically detected patches with a training data set of manually detected dark patches. The training data set includes oil slicks and lookalikes. As a result, the “best” preprocessing method that homogenizes the brightness of C-band SAR scenes and optimizes the automatic detection of marine oil slicks is based on an adaptation to the C-band MODel. As for the cleaning process, the tested morphological methods show that small object removal followed by a morphological closing optimizes the automatic detection of marine oil slicks. [ABSTRACT FROM AUTHOR]

The low-level temperature inversions have significant impacts on Arctic climate change feedbacks. The Atmospheric Infrared Sounder (AIRS) can extract the inversions over both land and ocean, and it is, however, sensitive to the presence of clouds. In this paper, we evaluate the effect of cloud fraction (CF) on AIRS inversions over both land and ocean. First, the AIRS inversions under clear-sky conditions are compared with the results from the microwave-based Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) observations in 2007–2013. Results show that despite the COSMIC and AIRS inversions appearing to be deeper and stronger in winter than in autumn, spring, and summer, the former is generally shallower and stronger than the latter in all seasons over both land and ocean. Time-series analysis of the mean monthly inversions from COSMIC and AIRS observations in 2007–2013 under both clear-sky and cloudy conditions further indicates that their differences are systematic and can be effectively mitigated after calibration under all sky conditions. Taking the calibrated COSMIC inversions as references, the AIRS inversion depths can be estimated with a root mean square (rms) of less than about 86 and 135 m, and the AIRS inversion strength can be obtained with an rms of better than about 1.7 °C and 1.3 °C under cloudy conditions over land and ocean, respectively. Moreover, while the AIRS inversion depths are insensitive to CF variations over both land and ocean, the inversion strengths are more sensitive to the CF variations over land than ocean. [ABSTRACT FROM AUTHOR]

Traditional marine monitoring systems such as oceanographic and hydrographic research vessels use either wireless sensor networks with a limited coverage, or expensive satellite communication that is not suitable for small and mid-sized vessels. This paper proposes a novel Internet of Marine Things data acquisition and cartography system in the marine environment using Very High Frequency (VHF) available on the majority of ships. The proposed system is equipped with many sensors such as sea depth, temperature, wind speed and direction, and the collected data is sent to 5G edge cloudlets connected to sink/base station nodes on shore. The sensory data is ultimately aggregated at a central cloud on the internet to produce up to date cartography systems. Several observations and obstacles unique to the marine environment have been discussed and feed into the solutions presented. The impact of marine sparsity on the network is examined and a novel hybrid Mobile Ad-hoc/Delay Tolerant routing protocol is proposed to switch automatically between Mobile Ad-hoc Network and Delay Tolerant Network routing according to the network connectivity. The low rate data transmission offered by VHF radio has been investigated in terms of the network bottlenecks and the data collection rate achievable near the sinks. A data synchronization and transmission approach has also been proposed at the 5G network core using Information Centric Networks. [ABSTRACT FROM PUBLISHER]

A model for scene simulation is presented, which describes quantitatively the recognized phenomenology of passive millimeter-wave (PMW) imaging in land, sea, and air scenarios. The model describes objects in a scene as facets giving them electromagnetic properties from their electrical permittivities. This enables polarimetric effects in scenes to be reproduced. Illumination from the sky and ground is calculated using radiation transport, as are the emissive and absorbing effects of the atmosphere between the objects and the imager. The model includes the effects of image sampling, diffraction effects of finite imager aperture sizes, and system noise. Phenomena in experimentally acquired images in the 94 GHz atmospheric transmission window are quantified from three scenarios. These are a helicopter landing site as viewed by the pilot, a coastal region showing boats, land and buildings viewed from sea level, and an airfield viewed from directly above. These are compared quantitatively to the simulated scenes from these scenarios, finding agreement between the radiation temperatures to within a few degrees kelvin. These discrepancies are accounted for by the uncertainties in the permittivities of materials in the scene. This paper constitutes the partial validation of a scene simulation capability for PMMW imaging in outdoor scenarios. [ABSTRACT FROM PUBLISHER]

The first two parts in this series gave full analysis and discussion of five high temperature insulation materials, i.e. PTFE, FEP, ETFE, PEEK, and PI over aspects of space charge behavior, conduction property as well as partial discharge, respectively. In this part, the degradation and surface breakdown properties are investigated and the related mechanism is discussed. The results showed that due to stable formation of C-F structures, PTFE and FEP melted locally during arc erosion test, with no carbon element being precipitated. At 25 °C, PI showed the best surface anti-arc erosion property among ETFE, PEEK and PI. However, compared with other samples, the arc withstand property of PI can be much more influenced at higher temperature and in case of surface contamination. Compared with the results measured at 25 °C, the surface flashover voltage decreased for all samples when measured at 150 °C, which can be explained by the expansion of “analogous ineffective region”. FEP has the highest surface flashover voltage at both 25 °C and 150 °C, which is due to higher surface roughness. The content of this paper provides a reference for aging characterization and evaluation of high temperature materials for DC cable and circuit board insulation. [ABSTRACT FROM AUTHOR]