The Japan Meteorological Agency (JMA) successfully launched the Himawari-8 (H-8) new-generation geostationary meteorological satellite with the Advanced Himawari Imager (AHI) sensor on October 7, ...2014. The H-8/AHI level-2 (L2) operational cloud property products were released by the Japan Aerospace Exploration Agency during September 2016. The Voronoi light scattering model, which is a fractal ice particle habit, was utilized to develop the retrieval algorithm called "Comprehensive Analysis Program for Cloud Optical Measurement" (CAPCOM-INV)-ice for the AHI ice cloud product. In this paper, we describe the CAPCOM-INV-ice algorithm for ice cloud products from AHI data. To investigate its retrieval performance, retrieval results were compared with 2000 samples of the ice cloud optical thickness and effective particle radius values. Furthermore, AHI ice cloud products are evaluated by comparing them with the MODIS collection-6 (C6) products. As an experiment, cloud property retrievals from AHI measurements, with an observation interval time of 2.5 min and ground-based rainfall observation radar data (the latter of which is supplied by the JMA, with a 1-km grid mesh), are used to investigate the generation processes of deep convective (DC) cloud in the vicinity of the Kyushu island, Japan. It revealed that AHI measurements have the capability of monitoring the growth processes, including variation of the cloud properties and the precipitation in the DC cloud.
Optical properties of clouds and heavy aerosol retrieved from satellite measurements are the most important elements for calculating surface solar radiation (SSR). The Himawari-8/Advanced Himawari ...Imager (AHI) satellite measurements receive high spatial, temporal and spectral signals, which provides an opportunity to estimate cloud, aerosol and SSR accurately.
In this study, we developed the AHI official cloud property product (version 1.0) for JAXA P-Tree system. A look-up table (LUT) method was used to calculate high-temporal (10 min) and high-spatial (5 km) SSR from AHI cloud properties. First, the LUT of the SSR estimation was optimized through a radiative transfer model to account for solar zenith angle, cloud optical thickness (COT), effective particle radius (CER), aerosol optical thickness and surface albedo. Following this, COT and CER were retrieved from the AHI data, with ice cloud parameters being retrieved from an extended Voronoi ice crystal scattering database and water cloud parameters being retrieved from the Mie–Lorenz scattering model. The retrieved COT and CER for water clouds were compared well with MODIS collection 6 cloud property products, with correlation coefficients of 0.77 and 0.82, respectively. The COT of ice cloud also shows good consistency, with a correlation coefficient of 0.85. Finally, the SSR was calculated based on the SSR LUT and the retrieved cloud optical parameters. The estimated SSR was validated at 122 radiation stations from several observing networks covering the disk region of Himawari-8. The root-mean-square error (RMSE) at CMA (China Meteorological Administration) stations was 101.86 Wm−2 for hourly SSR and 31.42 Wm−2 for daily SSR; RMSE at non-CMA stations was 119.07 Wm−2 for instantaneous SSR, 81.10 Wm−2 for hourly SSR and 26.58 Wm−2 for daily SSR. Compared with the SSR estimated from conventional geostationary satellites, the accuracy of the SSR obtained in this study was significantly improved.
•The AHI official cloud algorithm (version 1.0) is developed for the JAXA P-Tree system.•The Voronoi ice crystal scattering model is used to develop the ice cloud product.•High-accuracy SSR is estimated using the AHI cloud parameters.
We developed a scheme to improve hourly estimates of aerosol optical thickness (AOT) from the Advanced Himawari Imager (AHI) onboard Himawari-8, the Japan Meteorological Agency's latest geostationary ...satellite. Taking advantage of the sampling characteristics of the AHI (10-min temporal and subkilometer spatial resolution), we quantify temporal and spatial variability of AOT from the observations (AOT original ) and utilize this information to develop an hourly algorithm that produces two sets of derived AOTs: AOT pure , derived by the application of strict cloud screening to AOT original , and AOT merged , derived from spatial and temporal interpolations of AOT pure . The AOTs thus obtained from the hourly algorithm were validated against measurements from the aerosol robotic network. The root-mean-square errors (RMSEs) of the AOT pure and AOT merged products were 0.14 and 0.11, respectively, providing improvement over an RMSE of 0.20 for AOT original .
This study proposes a new approach that probes particle growth processes of liquid clouds with satellite observables from passive imagers. Based on the notion that the condensation growth and the ...coalescence process are characterized by constant cloud droplet number concentration (CDNC) and liquid water path (LWP), respectively, the method adopted used spatial variances of imager‐derived cloud properties to estimate relative contributions from these processes embedded in the cloud system. The relative standard deviations (RSDs) of CDNC and LWP associated with their horizontal variances were compared in the form of their ratio. This approach was applied to the GCOM‐C/SGLI cloud product, and spatial variability in this RSD ratio was consistent with cloud horizontal morphology such as open‐ and closed‐cell structures. The results suggest that spatial variances of imager‐derived cloud properties depict signatures of cloud microphysical processes in the way mappable on the horizontal extent of the cloud system.
Plain Language Summary
In low‐level clouds consisting of liquid water droplets, called warm clouds, droplets grow via the condensation and coalescence processes. The condensation process involves the growth of particles by absorption of water vapor and typically occurs in the early stages of cloud development. The coalescence process involves collision and coalescence with other particles and typically occurs when droplets grow to a size large enough for them to collide with each other. This study proposes a new approach that employs satellite observations to quantitatively estimate how these two processes occur in a given cloud system and to display it in the form of a geographical map of a quantity representing relative contributions of the two processes. The quantity was computed using spatial variances of satellite‐observed cloud properties such as cloud droplet number concentration and liquid water path to diagnose the two processes characterized by conservation of each property. The results highlight that spatial variability in relative contributions of the two processes was consistent with cloud horizontal morphology such as open‐ and closed‐cell structures that are identified as honeycomb‐like patterns of cloudiness. The proposed approach may serve as a satellite‐based way of “geographical process mapping” of warm clouds in the spatial context.
Key Points
Spatial variances of imager‐derived cloud properties were investigated in terms of conservation of number and mass concentrations
A methodology is shown for inferring the dominance of condensation or coalescence in cloud droplet growth using the spatial variances
Spatial variability in dominant cloud growth processes was consistent with cloud morphology such as open‐ and closed‐cell structures
We developed a common algorithm to retrieve aerosol properties, such as aerosol optical thickness, single-scattering albedo, and Ångström exponent for various satellite sensors over land and ocean. ...The three main features of this algorithm are: (1) automatic selection of the optimum channels for aerosol retrieval by introducing a weight for each channel to the object function, (2) setting common candidate aerosol models over land and ocean, and (3) preparing lookup tables for every 1 nm in the range of 300 to 2500 nm in the wavelength and weighting the radiance using the response function for each sensor. This method was applied to the Advanced Himawari Imager (AHI) on board the Japan Meteorological Agency's geostationary satellite Himawari-8, and the results depicted a continuous estimate of aerosol optical thickness over land and ocean. Furthermore, the aerosol optical thickness estimated using our algorithm was generally consistent with the products of the Moderate Resolution Imaging Spectroradiometer (MODIS) and Aerosol Robotic Network (AERONET). In addition, we applied our algorithm to MODIS on board the Aqua satellite and compared the retrieval results to the results obtained from AHI. The comparisons of the aerosol optical thickness, retrieved from different sensors with the different viewing angles onboard the geostationary and polar-orbiting satellites, suggest an underestimation of aerosol optical thickness at the backscattering direction (or overestimated in other directions). The retrieval of aerosol properties using a common algorithm allows in identifying a weakness in the algorithm, such as the assumptions in the aerosol model (e.g., sphericity or size distribution).
Pile-supported wharves undergo lateral displacement as well as structural damage due to earthquakes. Therefore, residual displacement and structural safety assessment are necessary for ...earthquake-resistant design of pile-supported wharves. This study introduces a simplified reliability estimation method for pile-supported wharves, involving the residual displacement caused by earthquakes and the variation of earthquake ground motions. As the residual displacement of wharves is strongly affected by the deformation of subsoil caused by earthquakes, a soil-structure system finite element earthquake response analysis was performed. To reduce the computational load for the evaluation of a probability distribution of residual displacement, a first-order second-moment method estimating the probabilistic response of structures with a small number of trials was applied. Thefinite element analyses demonstrate that the summed squared Fourier amplitudes (SSFAs) of the input seismic motion for a cumulative probability frequency band better estimated the residual displacement. A simplified reliability estimation method utilizing three results of finite element analyses is proposed following the demonstration of its applicability.
•Sum of squared Fourier amplitude of waveform for evaluating residual displacement.•Three results of FEA for probability distribution estimation of residual displacement.•Reliability index estimation by use of First-order second-moment method.
The nature of progenitors of the so-called super-Chandrasekhar candidate Type Ia supernovae (SC-SNe Ia) has been actively debated. Recently, Yamanaka et al. reported a near-infrared (NIR) excess for ...SN 2012dn and proposed that the excess originates from an echo by circumstellar (CS) dust. In this paper, we examine a detailed distribution of the CS dust around SN 2012dn and investigate implications of the CS dust echo scenario for general cases of SC-SNe Ia. We find that a disk/bipolar CS medium configuration reproduces the NIR excess fairly well, where the radial density distribution is given by a stationary mass loss. The inner radius of the CS dust is 0.04 pc. The mass-loss rate of the progenitor system is estimated to be and M yr−1 for the disk and bipolar CS medium configurations, respectively, which adds further support for the single-degenerate scenario. Our models limit SN 2009dc, another SC-SN Ia, to have a dust mass less than 0.16 times that of SN 2012dn. While this may merely indicate some variation on the CS environment among SC-SNe Ia, this could raise another interesting possibility. There could be two classes among SC-SNe Ia: the brighter SC-SNe Ia in a clean environment (SN 2009dc) and the fainter SC-SNe Ia in a dusty environment (SN 2012dn).
Type IIP supernovae (SNe IIP) often show relatively high continuum polarization (∼1%) in the late phase. This polarization feature is generally believed to be due to an inner aspherical core revealed ...in the late phase, while this polarization feature can also be contributed by the effect of polarized-scattered echoes by circumstellar (CS) dust around the SN. In this paper, we propose a unique method to distinguish polarization from the SN ejecta and from the light echo. We quantitatively examine wavelength dependence of the polarization created by the scattered echoes for various geometries and amounts of CS dust. It is found that the polarization in the U-band has characteristic features, i.e., the polarization emerges at an earlier phase with higher polarization degree than that in longer wavelengths. These are due to the rapid evolution of the U-band light curve as well as higher optical depth of dust in shorter wavelengths. Except for the U band, the polarization increases after the plateau phase, and the polarization degree is generally higher for shorter wavelengths. These polarimetric features can be easily distinguished from the polarization expected from an aspherical core, which predicts almost no wavelength dependence. Moreover, we show that multi-band polarimetric observations for SNe IIP can constrain a parameter space in the CS dust mass and distance from the SNe. We thus encourage multi-band polarimetric observations for SNe IIP.
Prestressed concrete piles with closed-ended circular hollow sections (spun piles) are sometimes used as foundations for pile-supported wharves. Due to a reduction in the rebar area, concrete ...compressive strength, yield strength of PC-bar, and bond strength between PC-bar and concrete, corrosion attacks typically lower the performance of spun piles in the marine environment. A comprehensive analysis of the corrosion effect on the mechanical properties of the spun pile materials is crucial to assess the performance of corroded spun plies. Using a three-dimensional finite element analysis (FEA), this study aimed to evaluate the impact of corrosion on the mechanical properties of the material used in spun pile construction. We simulated the effect of nonuniformly distributed corrosion products using a volumetric strain expansion over 0–75 years. The FEA results provided the stress–strain relationship of the corroded spun pile materials and the bond–slip relationship between the corroded PC-bar and concrete. We proposed equations for predicting the deterioration degree of the mechanical properties of corroded spun pile materials and compared them to those presented in previous studies. It was shown that the compressive strength of the corroded cover concrete decreased significantly after the corrosion degree reached 12%, which the previous research had not expected. The bond strength reduction was inverse exponential against the elapsed years after the corrosion degree reached 1.3%. Moreover, the yield strength of PC-bars decreased linearly with the increase in the corrosion degree.
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