Shift-and-add reconstruction of solar granulation images

To restore an atmospherically degraded image of solar granulation the shift-and-add (SAA) method is applied to its specklegrams. It is the first time, to the best of our knowledge, that such a technique has been used for image reconstruction of solar granulation, a largely extended target. SAA, therefore, enables us to monitor restored images of solar granulation in a simple and fast way.     

Consequences of implementing a reservoir operation algorithm in a global hydrological model under multiple meteorological forcing

We investigated dam behaviours during high-flow events and their robustness against perturbations in meteorological conditions using the H08 global hydrological model. Differences in these behaviours were examined by comparing simulation runs, with and without dams and using multiple meteorological datasets, at a case-study site, Fort Peck Dam on the Missouri River, USA. The results demonstrated that dam-regulated river flow reduced temporal variability over large time periods and also dampened inter-forcing discrepancies in river discharge (smoothing effects). However, during wet years, differences in peak flow were accentuated downstream of the dam, resulting in divergence in simulated peak flow across the meteorological forcing (pulsing effect). The pulsing effect was detected at other major dams in global simulations. Depending upon the meteorological forcing, the dams act as a selective filter against high-flow events. Synergy between a generic dam scheme and differences in meteorological forcing data might introduce additional uncertainties in global hydrological simulations.     

A New Solar Imaging System for Observing High-Speed Eruptions: <Emphasis Type="Italic">Solar Dynamics Doppler Imager</Emphasis> (SDDI)

A new solar imaging system was installed at Hida Observatory to observe the dynamics of flares and filament eruptions. The system (Solar Dynamics Doppler Imager; SDDI) takes full-disk solar images with a field of view of \(2520~\mbox{arcsec} \times 2520~\mbox{arcsec}\) at multiple wavelengths around the \(\mathrm{H}\alpha\) line at 6562 Å. Regular operation was started in May 2016, in which images at 73 wavelength positions spanning from \(\mathrm{H}\alpha -9~\mathring{\mathrm{A}}\) to \(\mathrm{H}\alpha +9~\mathring{\mathrm{A}}\) are obtained every 15 seconds. The large dynamic range of the line-of-sight velocity measurements (\({\pm}\,400~\mbox{km}\,\mbox{s}^{-1}\)) allows us to determine the real motions of erupting filaments in 3D space. It is expected that SDDI provides unprecedented datasets to study the relation between the kinematics of filament eruptions and coronal mass ejections (CME), and to contribute to the real-time prediction of the occurrence of CMEs that cause a significant impact on the space environment of the Earth.     

Temperature scaling pattern dependence on representative concentration pathway emission scenarios A letter

To preserve consistency among developed emission scenarios, the scenarios used in climate modeling, and the climate scenarios available for impact research, the pattern scaling technique is useful technique. The basic assumption of pattern scaling is that the spatial response pattern per 1 K increase in the global mean surface air temperature (SAT) (scaling pattern) is the same among emission scenarios, but this assumption requires further validation. We therefore investigated the dependence of the scaling pattern of the annual mean SAT on GHGs emission scenarios of representative concentration pathways (RCP) and the causes of that dependence using the Model for Interdisciplinary research on Climate 5 developed by Japanese research community. In particular, we focused on the relationships of the dependency with effects of aerosols and Atlantic meridional overturning circulation. We found significant dependencies of the scaling pattern on emission scenarios at middle and high latitudes of the Northern Hemisphere, with differences of >15 % over parts of East Asia, North America, and Europe. Impact researchers should take into account those dependencies that seriously affect their research. The mid-latitude dependence is caused by differences in sulfate aerosol emissions per 1 K increase in the global mean SAT, and the high-latitude dependence is mainly caused by nonlinear responses of sea ice and ocean heat transport to global warming. Long-term trends in land-use and land-cover changes did not significantly affect the scaling pattern of annual mean SAT, but they might have an effect at different timescales.     

Emission scenario dependencies in climate change assessments of the hydrological cycle

Anthropogenic global warming will lead to changes in the global hydrological cycle. The uncertainty in precipitation sensitivity per 1 K of global warming across coupled atmosphere-ocean general circulation models (AOGCMs) has been actively examined. On the other hand, the uncertainty in precipitation sensitivity in different emission scenarios of greenhouse gases (GHGs) and aerosols has received little attention. Here we show a robust emission-scenario dependency (ESD); smaller global precipitation sensitivities occur in higher GHG and aerosol emission scenarios. Although previous studies have applied this ESD to the multi-AOGCM mean, our surprising finding is that current AOGCMs all have the common ESD in the same direction. Different aerosol emissions lead to this ESD. The implications of the ESD of precipitation sensitivity extend far beyond climate analyses. As we show, the ESD potentially propagates into considerable biases in impact assessments of the hydrological cycle via a widely used technique, so-called pattern scaling. Since pattern scaling is essential to conducting parallel analyses across climate, impact, adaptation and mitigation scenarios in the next report from the Intergovernmental Panel on Climate Change, more attention should be paid to the ESD of precipitation sensitivity.     

Particle-Image Velocimetry Measurements of Separation and Re-attachment of Airflow over Two-Dimensional Hills with Various Slope Angles and Approach-Flow Characteristics

Airflow over two-dimensional hills was investigated in a wind tunnel using particle image velocimetry. We focus on the flow separation behaviour. A trapezoidal hill shape was used in most of the experimental runs, but the critical slope angle for flow separation was approximately the same as that established for smooth hill shapes. The re-attachment point of the separated flow became farther from the hill as the slope angle $\theta $ increased, reaching a saturation of about seven times the hill height for $\theta \gtrsim 60^\circ $ . Increasing the upwind surface roughness length was found to suppress flow separation. This tendency is analogous to the previous experimental results for turbulent boundary layers on flat plates. The boundary-layer thickness varied by the presence or absence of Counihan-type spires and a castellated fence at the test-section entrance had negligible effect on the flow separation.     

Narrower grid structure of artificial reef enhances initial survival of in situ settled coral

The initial factors that cause a decline in the survival of in situ settled corals remain poorly understood. In this study, we demonstrated through field experiments that the design of artificial grid plates may influence the initial survival of Acropora corals, with narrower grids being the most effective. In fact, grid plates with a 2.5-cm mesh presented the highest recorded survival rate (14%) at 6 months after settlement (representing approximately 50 corals per 0.25 m² of plate). This is the first study where such high survival rates, matching those of cultures under aquarium conditions, were obtained in the field without using additional protective measures, such as guard nets against fish grazing after seeding. Therefore, our results provide a foundation for establishing new and effective coral restoration techniques for larval seeding, in parallel to clarifying the details of the early life stages of reef-building corals.     

Strength of single-crystal orthopyroxene under lithospheric conditions

Creep strength of oriented orthopyroxene single crystals was investigated via shear deformation experiments under lithospheric conditions [P (pressure) = 1.3 GPa and T (temperature) = 973–1,373 K]. For the A-orientation (shear direction [001] on (100) plane), the samples have transformed completely to clinoenstatite and much of the deformation occurred after transformation. In contrast, for the B-orientation (shear direction [001] on (010) plane), samples remained orthoenstatite and deformation occurred through dislocation motion in orthoenstatite. The strength of orthopyroxene with these orientations is smaller than for olivine aggregates under all experimental conditions. Flow of the B-orientation samples is described by a power-law, and the pre-exponential constant, the apparent activation energy, and the stress exponent are determined to be A = 10^−9.5 s⁻¹·MPa^−4.2, Q = 114 kJ/mol and n = 4.2. However, for the A-orientation, the results cannot be fit by a single flow law and we obtained the following: A = 10^8.9 s⁻¹·MPa^−3.0, Q = 459 kJ/mol and n = 3.0 at high temperatures (≥1,173 K), and A = 10^−27.4 s⁻¹·MPa^−14.3, Q = 296 kJ/mol and n = 14.3 at low temperatures (<1,173 K). The stress exponent for the low-temperature regime is high, suggesting that deformation involves some processes where the activation energy decreases with stress such as the Peierls mechanism. Our study shows that orthopyroxene with these orientations is significantly weaker than olivine under the lithospheric conditions suggesting that orthopyroxene may reduce the strength of the lithosphere, although the extent to which orthopyroxene weakens the lithosphere depends on its orientation and connectivity.     

Electron precipitation and mass motion in the 1991 June 9 white-light flare

We use H line profiles as a diagnostic of mass motion and nonthermal electron precipitation in the white-light flare (WLF) of 1991 June 9 01:34 UT. We find only weak downflow velocities (10 km s^–1) at the site of white-light emission, and comparable velocities elsewhere.We also find that electron precipitation is strongest at the WLF site. We conclude that continuum emission in this flare was probably caused by nonthermal electrons and not by dynamical energy transport via a chromospheric condensation.