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The organization of clouds has been widely studied by numerical modeling as an essential problem in climate science. Convective self-aggregation (CSA) occurs in radiative–convective equilibrium when the model domain size is sufficiently large. However, we have not yet reached a comprehensive understanding of the mechanism of CSA onset. This study argues that low-level circulation is responsible for horizontal moisture transport and that its coupling with variabilities of diabatic heating and moisture in the free troposphere is essential. We simulated scattered and aggregated convection by varying the domain size as a control parameter constraining the horizontal scale associated with the CSA onset. Based on a new analysis method quantifying the circulation spanning dry and moist regions, we found that 1) the upgradient moisture transport in the aggregated cases is associated with low-level circulation development, amplifying the horizontal moisture contrast; 2) the horizontal buoyancy gradient due to strong radiative cooling in the dry region intensifies the low-level circulation; 3) the free-tropospheric subsidence intrudes into the boundary layer in the dry region preceding the intensification of low-level circulation; and 4) the subsidence intrusion is due to a weakening of convective heating in the free troposphere associated with the moisture variability at a larger horizontal scale. This study provides new insights into the organization mechanism of clouds unifying the different mechanisms impacting CSA: the free-tropospheric moisture, radiation, convection, and low-level circulation.

Convective variability is used to diagnose different pathways towards convective self-aggregation (CSA) in radiative-convective equilibrium simulations with two cloud-resolving models, SCALE and VVM. The results show that convection undergoes gradual growth in SCALE and fast transition in VVM, which is associated with different mechanisms between the two models. In SCALE, strong radiative cooling associated with a dry environment drives the circulation from the dry region, and the dry environment results from strong subsidence and insufficient surface flux supply. The circulation driven by the radiative cooling then pushes convection aggregating, which is the dry-radiation pathway. In VVM, CSA develops due to the rapid strengthening of circulation driven by convective systems in the moist region, which is the convection-upscaling pathway. The different pathways of CSA development can be attributed to the upscale process of convective structures identified by the cloud size spectrum. The upscaling of large-size convective systems can enhance circulation from the moist region in VVM. In SCALE, the infrequent appearance of large convective systems is insufficient to generate circulation, as compensating subsidence can occur within the moist region even in the absence of convective systems. This study shows that the convective variabilities between models can lead to different pathways of CSA, and mechanism-denial experiments also support our analyses.

Putrescine is a bioactive polyamine. Its retinal concentration is strictly controlled to maintain a healthy sense of vision. The present study investigated putrescine transport at the blood–retinal barrier (BRB) to gain a better understanding of the mechanisms of putrescine regulation in the retina. Our microdialysis study showed that the elimination rate constant during the terminal phase was significantly greater (1.90-fold) than that of [14C]D-mannitol, which is a bulk flow marker. The difference in the apparent elimination rate constants of [3H]putrescine and [14C]D-mannitol was significantly decreased by unlabeled putrescine and spermine, suggesting active putrescine transport from the retina to the blood across the BRB. Our study using model cell lines of the inner and outer BRB showed that [3H]putrescine transport was time-, temperature-, and concentration-dependent, suggesting the involvement of carrier-mediated processes in putrescine transport at the inner and outer BRB. [3H]Putrescine transport was significantly reduced under Na+-free, Cl−-free, and K+-replacement conditions, and attenuated by polyamines or organic cations such as choline, a choline transporter-like protein (CTL) substrate. Rat CTL1 cRNA-injected oocytes exhibited marked alterations in [3H]putrescine uptake, and CTL1 knockdown significantly reduced [3H]putrescine uptake in model cell lines, suggesting the possible participation of CTL1 in putrescine transport at the BRB.

This paper describes and analyzes the Reed-Jablonowski (RJ) tropical cyclone (TC) test case used in the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016). The intermediate complexity test case analyzes the evolution of a weak vortex into a TC in an idealized tropical environment. Simulations from 9 general circulation models (GCMs) that participated in DCMIP2016 are analyzed in this study at 50 km horizontal grid spacing, with 5 of these models also providing simulations at 25 km grid spacing for an analysis on the impact of finer grid spacing. Evolution of minimum surface pressure (MSP) and maximum 1 km azimuthally averaged wind speed (MWS), the wind-pressure relationship, radial profiles of wind speed and surface pressure, and wind composites are documented for all participating GCMs at both horizontal grid spacings. While results are generally similar between all models, some GCMs reach significantly higher storm intensities than others, ultimately impacting specific characteristics of their horizontal and vertical structure. TCs simulated at 25 km grid spacings retained these differences, but reach higher intensities and are more compact than their 50 km counterparts. These results indicate dynamical core choice is an essential factor in GCM development, and future work should be conducted to explore how specific differences within the dynamical core affect TC behavior in GCMs.

Toward the achievement of reliable global kilometer-scale (k-scale) climate simulations, we improve the Nonhydrostatic ICosaherdral Atmospheric Model (NICAM) by focusing on moist physical processes. A goal of the model improvement is to establish a configuration that can simulate realistic fields seamlessly from the daily-scale variability to the climatological statistics. Referring to the two representative configurations of the present NICAM, of which each has been used for climate-scale and sub-seasonal-scale experiments, we try to find the appropriate partitioning of fast/local and slow/global-scale circulations. In a series of sensitivity experiments at 14-km horizontal mesh, (1) the tuning of terminal velocities of rain, snow, and cloud ice, (2) the implementation of turbulent diffusion by the Leonard term, and (3) enhanced vertical resolution are tested. These tests yield reasonable convection triggering and convection-induced tropospheric moistening, and result in better performance than in previous NICAM climate simulations. In the mean state, double Intertropical Convergence Zone bias disappears, and the zonal contrast of equatorial precipitation, top-of-atmosphere radiation balance, vertical temperature profile, and position/strength of subtropical jet are dramatically better reproduced. Variability such as equatorial waves and the Madden–Julian oscillation (MJO) is spontaneously realized with appropriate spectral power balance, and the Asian summer monsoon, boreal-summer MJO, and tropical cyclone (TC) activities are more realistically simulated especially around the western Pacific. Meanwhile, biases still exist in the representation of low-cloud fraction, TC intensity, and precipitation diurnal cycle, suggesting that both finer spatial resolutions and the further model development are warranted.

The eastward movement of a convectively active region is a distinguishing characteristic of the Madden–Julian oscillation (MJO). However, knowledge about the mechanisms that determine the eastward movement speed remains limited. This study investigates how the background environment modulates the speed of the boreal winter MJO and describes an intrinsic relationship between the MJO and background atmospheric circulation. We calculated the speed of the MJO events from the daily tracking of the locations of the minimum values of the outgoing longwave radiation anomaly in the time–longitude space. These speeds were then used to analyze systematic differences in the sea surface temperature (SST) distribution associated with the MJO speed. The analysis revealed a deceleration of the MJO under low-frequency (>90 days) SST distributions that increased toward the western Pacific from both the Indian Ocean and the eastern Pacific. In contrast, the dependency on SST variability in intraseasonal frequencies (20–90 days) was small. Subsequently, the relationship between the MJO speed and background circulation, which is largely determined by the lower boundary condition set by the low-frequency SST distribution, was analyzed. The analysis counterintuitively revealed that the MJO tends to decelerate when the large-scale zonal circulation with low-level westerlies and upper-level easterlies from the Indian Ocean to the Maritime Continents is strong. The results suggest a novel view that the MJO is an integral component of the Walker circulation and that its eastward movement is modulated by the state of the large-scale flow of the Walker circulation.

Observations show that sea surface temperatures along the Gulf Stream and the Kuroshio Current tend to synchronize at decadal time scales. This synchronization, which we refer to as the boundary current synchronization (BCS), is reproduced in global climate models with high spatial resolution. Both in observations and model simulations, BCS is associated with meridional migrations of the atmospheric jet stream. Changes in the strength and path of the ocean currents associated with the jet shifts lead to the synchronicity of surface temperatures. Numerical simulations using a conceptual model and an atmospheric general circulation model are consistent with a notion that BCS is an interbasin air-sea coupled mode. Air temperature patterns similar to the one associated with BCS have been repeatedly observed, including in July of 1994 and 2018.

Biological motions commonly contain multiple frequency components in which each fundamental has to be adjusted by motor learning to acquire a new motor skill or maintain acquired skills. At times during this motor performance one frequency component needs to be enhanced (gain-up) while another is suppressed (gain-down). This pattern of simultaneous gain-up and -down adjustments at different frequencies is called frequency competitive motor learning. Currently we investigated cerebellar roles in this behavior utilizing the goldfish vestibulo-ocular reflex (VOR). Previously, VOR motor learning was shown in primates to be frequency selective and exhibit frequency competitive motor learning. Here we demonstrate that the goldfish VOR performs frequency competitive motor learning when high and low frequency components are trained to gain-up and gain-down, respectively. However, when the two frequency components were trained in the opposite directions only gain-up component was observed. We also found that cerebellectomy precluded any frequency competitive VOR motor learning. Complementary single unit recordings from vestibulo-cerebellar Purkinje cells revealed changes in firing modulation along with gain-down learning, but not with gain-up learning irrespective of frequency. These results demonstrate that the cerebellum is required for all frequency competitive VOR motor learning and Purkinje cell activity therein is well correlated with all gain-down behaviors independent of frequency. However, frequency competitive gain-up learning requires intact, recursive brainstem/cerebellar pathways. Collectively these findings support the idea that VOR gain-up and gain-down learning utilize separate brainstem/cerebellar circuitry that, in turn, clearly underlies the unique ability of the oculomotor system to deal with multiple frequency components.

The terminal velocity of cloud drops and raindrops used in numerical model calculations can significantly affect weather predictions. Current formulations rely on laboratory experiments made in the 1940s and 1960s. Because these experiments were performed only at typical environmental conditions of 20°C and 1013 hPa, parameterizations have been introduced to deduce the terminal velocity aloft without rigorous evaluation. In this study, an incompressible two-phase flow direct numerical simulation model is used to calculate the free-falling motion of axisymmetric drops with diameters between 0.025 and 0.5 mm to study the terminal fall velocity. Simulated terminal fall velocities of free-falling drops at 20°C and 1013 hPa agree within 3.2% with the previous empirical parameterization (Beard formula), and 4.5% with existing laboratory data in the diameter range between 0.3 and 0.5 mm. The velocities converge to the analytic Hadamard–Rybczynski solution within 2% for small Reynolds numbers, demonstrating the robustness of our simulations. Simulations under various atmospheric conditions show that existing empirical parameterizations that account for the air density dependence of the terminal velocity have errors up to 11.8% under the conditions examined in this study. We propose a new empirical formula that describes the air density dependence of the terminal velocity. It is also shown that the falling speed of a small drop is not sensitive to shape oscillation, and the terminal velocity decreases by only less than 1.3% when the axis ratio increases by 12% with reduced surface tension. Internal circulation within falling drops is also presented and compared with previous studies.

The Nonhydrostatic ICosahedral Atmospheric Model (NICAM), a global model with an icosahedral grid system, has been under development for nearly two decades. This paper describes NICAM16-S, the latest stable version of NICAM (NICAM.16), modified for the Coupled Model Intercomparison Project Phase 6, High Resolution Model Intercomparison Project (HighResMIP). Major updates of NICAM.12, a previous version used for climate simulations, included updates of the cloud microphysics scheme and land surface model, introduction of natural and anthropogenic aerosols and a subgrid-scale orographic gravity wave drag scheme, and improvement of the coupling between the cloud microphysics and the radiation schemes. External forcings were updated to follow the protocol of the HighResMIP. A series of short-term sensitivity experiments were performed to determine and understand the impacts of these various model updates on the simulated mean states. The NICAM16-S simulations demonstrated improvements in the ice water content, high cloud amount, surface air temperature over the Arctic region, location and strength of zonal mean subtropical jet, and shortwave radiation over Africa and South Asia. Some long-standing biases, such as the double intertropical convergence zone and smaller low cloud amount, still exist or are even worse in some cases, suggesting further necessity for understanding their mechanisms, upgrading schemes and parameter settings, and enhancing horizontal and vertical resolutions.

In the zonal direction, the downward branch of the Walker circulation above the Indian Ocean is only 20 degrees thick, whereas the Pacific counterpart is 90 degrees thick. This zonal sharpness is r...

A possibly important dynamical process for the Madden–Julian oscillation (MJO) convective initiation is proposed. An MJO event during the "CINDY2011" field campaign is triggered by eastward-moving ...

A shallow-water model using the hexagonal synchronized B grid (SB grid) is developed on the spherical icosahedral grid. The SB grid adopts the same variable arrangement as the ZM grid, but does not suffer from a computational mode problem of the ZM grid since interactions in the extra degrees of freedom of velocity fields through the nonlinear terms are excluded. For better representations of the geostrophic balance, a quadratic reconstruction of fluid height inside hexagonal/pentagonal cells is used to configure the gradient with the second-order accuracy. When nongeostrophic motions are more dominant than geostrophic ones, smaller-scale noises arise. To prevent a decoupling of the velocity fields, a hyperviscosity is added to force velocities adjacent to each other to evolve synchronously. Some standard tests are performed to examine the SB-grid shallow-water model. The model is almost second-order accurate if both the initial conditions and the surface topography are smooth and if the influence of the hyperviscosity is small. The SB-grid model is superior to a C-grid model regarding the convergence of error norms in a steady-state geostrophically balanced flow test, while it is inferior to that concerning conservation of total energy in a case of flow over an isolated mountain. An advantage of the SB-grid model is that both accuracy and stability are weakly sensitive to whether a grid optimization is applied or not. The SB grid is an attractive alternative to the conventional A grid and is competitive with the C grid on the spherical icosahedral grid.

The structures and formation mechanisms of cirrus banding are investigated by analyzing radiosonde observations, conducting high-resolution numerical experiments, and performing linear stability analyses. In all 29 cases of cirrus bands that were analyzed, radiosonde observational data indicate that statically unstable layers exist. The detected banding clouds were aligned nearly parallel to the vertical shear vector in the unstable layer. In high-resolution numerical experiments using the cloud-resolving model SCALE-RM, cirrus bands forming in the outflow layer of a tropical cyclone are explicitly simulated. The existence of statically unstable layers and band-parallel background vertical wind shear are commonly identified in the simulations. Sensitivity experiments and heat budget analyses demonstrated that the unstable stratification within the cirrus clouds was maintained by the cloud-radiation interactions. To reveal the behavior of fluid instabilities in the cirrus bands, linear stability analyses in a basic state constructed from the radiosonde observations were performed. The fastest-growing disturbance is highly similar to that of the previously known thermal-shear instability in a uniform and isolated unstable layer and the results obtained by radiosonde observations and numerical simulations. All of the results consistently indicate that thermal-shear instability is responsible for the formation of cirrus banding. Our results not only follow previous modeling studies but also provide observational support, quantification of the destabilization by the cloud-radiation interactions, as well as a theoretical basis of the thermal-shear instability in a complex environment near cirrus bands.

The Non-hydrostatic ICosahedral Atmospheric Model (NICAM), a global model with an icosahedral grid system, has been under development for nearly two decades. Here, we present its recent updates for the Coupled Model Intercomparison Project Phase 6, High Resolution Model Intercomparison Project (HighResMIP) and their impact on the simulated mean states using 56-14km mesh model. Major updates include updates of the cloud microphysics scheme and land surface model, introduction of natural and anthropogenic aerosols and a subgrid-scale orographic gravity wave drag scheme, and improvement of the coupling between the cloud microphysics and the radiation schemes. A short-term sensitivity experiments demonstrate improvements in the ice water content, high cloud amount, surface air temperature over the Arctic region, location and strength of zonal mean subtropical jet, and shortwave radiation over Africa and South Asia. The decadal climate simulations further reveal an improvement in the genesis and structure of the tropical cyclones compared with those with the previous model. Finally, we will address outlook toward the cloud-resolving climate simulation based on a fresh benchmark result on supercomputer Fugaku, a flagship supercomputer in Japan.

The biogenesis of peroxisomes in relation to the trafficking of proteins to peroxisomes has been extensively examined. However, the supply of phospholipids, which is needed to generate peroxisomal membranes in mammals, remains unclear. Therefore, we herein investigated metabolic alterations induced by clofibric acid, a peroxisome proliferator, in the synthesis of phospholipids, particularly phosphatidylethanolamine (PE) molecular species, and their relationship with the biogenesis of peroxisomal membranes. The subcutaneous administration of clofibric acid to rats at a relatively low dose (130 mg/kg) once a day time-dependently and gradually increased the integrated perimeter of peroxisomes per 100 μm2 hepatocyte cytoplasm (P A ). A strong correlation was observed between the content (μmol/mg DNA) of PE containing arachidonic acid (20:4) and P A (r2 = 0.9168). Moreover, the content of PE containing octadecenoic acid (18:1) positively correlated with P A (r2 = 0.8094). The treatment with clofibric acid markedly accelerated the formation of 16:0–20:4 PE by increasing the production of 20:4 and the activity of acyl chain remodeling of pre-existing PE molecular species. Increases in the acyl chain remodeling of PE by clofibric acid were mainly linked to the up-regulated expression of the Lpcat3 gene. On the other hand, clofibric acid markedly increased the formation of palmitic acid (16:0)–18:1 PE through de novo synthesis. These results suggest that the enhanced formation of particular PE molecular species is related to increases in the mass of peroxisomal membranes in peroxisome proliferation in the liver.

NICAM, a nonhydrostatic global atmospheric model with an icosahedral grid system, has been developed for nearly two decades. This paper describes NICAM16-S, the latest stable version of NICAM (NICAM.16) modified for Coupled Model Intercomparison Project Phase 6 (CMIP6). Major updates from NICAM.12, a previous version used for climate simulations, include updates of a cloud microphysics scheme and a land model, an introduction of natural and anthropogenic aerosols and a subgrid-scale orographic gravity wave drag, and improvement of coupling between cloud microphysics and radiation schemes. External forcings were updated to follow a protocol of CMIP6 High Resolution Model Intercomparison Project (HighResMIP). A series of short-term sensitivity experiments were performed to check and understand impacts of the model updates on the simulated mean states. Improvements in the ice water content, the high cloud amounts, the surface air temperature over the Arctic region, the location and the strength of zonal mean subtropical jet, and shortwave radiation over the Africa and the South Asia were found in the NICAM16-S simulations. Some long-standing biases such as the double intertropical convergence zone and smaller low cloud amounts still exist or even worsen in some cases, suggesting further necessity for understanding their mechanisms and upgrading schemes and/or their parameter settings as well as for enhancing horizontal and vertical resolutions.

An environment favorable for the development of the Madden–Julian oscillation (MJO) was investigated by classifying MJO-like atmospheric patterns as MJO and regionally confined convective (RCC) events. Comparison of MJO and RCC events showed that even when preceded by a major convective suppression event, convective events did not develop into an MJO when large-scale buildup of moist static energy (MSE) was inhibited. The difference in the MSE accumulation between MJO and RCC is related to the contrasting low-frequency basic-state sea surface temperature (SST) pattern; the MJO and RCC events were associated with anomalously warm and cold low-frequency SSTs prevailing over the western to central Pacific, respectively. Differences in the SST anomaly field were absent from the intraseasonal frequency range of 20–60 days. The basic-state SST pattern associated with the MJO was characterized by a positive zonal SST gradient from the Indian Ocean to the western Pacific, which provided a long-standing condition that allowed for sufficient buildup of MSE across the Indian Ocean to the western Pacific via large-scale low-level convergence over intraseasonal and longer time scales. The results of this study suggest the importance of such a basic-state SST, with a long-lasting positive zonal SST gradient, for enhancing convection over a longer than intraseasonal time scale in realizing a complete MJO life cycle.

Foam separation method can effectively remove alkali metal ions from anionic surfactant solution by a combination of an air bubble generator and the flotation system. The alkali metal ions in the solution electrostatically adsorb onto the many bubbles by bubbling ionic surfactant solution and they transfer to the air/water interface. These bubbles change to the foam state that is removed using a long glass tube. The typical experimental system was composed of sodium dodecyl sulfate (SDS) as an anionic surfactant and the target alkali ions (Li, K, Rb, and Cs). Therefore, selective competition for air bubbles exists between the sodium (counterion of the surfactant) and target alkali ions. The removal rate of the alkali metal was noticeably dependent on surfactant concentration. The surfactant was effective in removing the alkali metal below the critical micelle concentration (CMC). The removal rate increased with increasing atomic number or crystal ion radius: Li

Sea surface temperatures (SSTs) of the Gulf Stream and the Kuroshio are shown to be synchronized for the decadal time scale. This synchronization, which we refer to as the Boundary Current Synchronization (BCS), is associated with meridional migrations of the atmospheric jet stream. The singular value decomposition (SVD) between SST and zonal wind shows that, within the context of known climate modes, BCS can be understood as the covariability shared by the Pacific Decadal Oscillation and the Northern Annular Mode. Nevertheless, because the SVD time series exhibit high correlations with the zonal-mean meridional SST difference between the subtropics and the midlatitudes, BCS can be understood more simply as an oceanic annular mode. Air temperature regressed on the BCS index exhibits a similar spatial pattern to temperature observed in July 2018.

This paper describes the splitting supercell idealized test case used in the 2016 Dynamical Core Model Intercomparison Project (DCMIP2016). These storms are useful test beds for global atmospheric models because the horizontal scale of convective plumes is O(1 km), emphasizing non-hydrostatic dynamics. The test case simulates a supercell on a reduced-radius sphere with nominal resolutions ranging from 4 to 0.5 km and is based on the work of Klemp et al. (2015). Models are initialized with an atmospheric environment conducive to supercell formation and forced with a small thermal perturbation. A simplified Kessler microphysics scheme is coupled to the dynamical core to represent moist processes. Reference solutions for DCMIP2016 models are presented. Storm evolution is broadly similar between models, although differences in the final solution exist. These differences are hypothesized to result from different numerical discretizations, physics–dynamics coupling, and numerical diffusion. Intramodel solutions generally converge as models approach 0.5 km resolution, although exploratory simulations at 0.25 km imply some dynamical cores require more refinement to fully converge. These results can be used as a reference for future dynamical core evaluation, particularly with the development of non-hydrostatic global models intended to be used in convective-permitting regimes.