Kohei Yoshida

Over 5,000 Years of Ensemble Future Climate Simulations by 60-km Global and 20-km Regional Atmospheric Models

AbstractAn unprecedentedly large ensemble of climate simulations with a 60-km atmospheric general circulation model and dynamical downscaling with a 20-km regional climate model has been performed to obtain probabilistic future projections of low-frequency local-scale events. The climate of the latter half of the twentieth century, the climate 4 K warmer than the preindustrial climate, and the climate of the latter half of the twentieth century without historical trends associated with the anthropogenic effect are each simulated for more than 5,000 years. From large ensemble simulations, probabilistic future changes in extreme events are available directly without using any statistical models. The atmospheric models are highly skillful in representing localized extreme events, such as heavy precipitation and tropical cyclones. Moreover, mean climate changes in the models are consistent with those in phase 5 of the Coupled Model Intercomparison Project (CMIP5) ensembles. Therefore, the results enable the a...

Synthesis and thermoresponsive properties of four-arm star-shaped poly(N-isopropylacrylamide)s bearing covalent and non-covalent cores

The present study describes the precise synthesis and thermoresponsive properties of two types of four-arm star-shaped poly(N-isopropylacrylamide)s (PNIPAM), i.e., the covalently linked one (3) and the non-covalently Ru(II)-chelated one (5). The atom transfer radical polymerization (ATRP) method was used to prepare the azido-terminated PNIPAM (1) arm using (2-azidoethyl)-2-chloropropionamide (AECP) as the initiator. 3 was subsequently prepared based on the click reaction of 1 with a multifunctional linker of tetra[(5-hexynyloyloxy)methyl]methane. For comparison, its linear counterpart 2 was also synthesized as a reference polymer by the same method using ethyl 5-hexynyloate. The four-arm star-shaped PNIPAM Ru complex 5, on the other hand, was prepared by a click-to-chelate approach, which involves the click reaction of 1 with 2,6-diethynylpyridine to produce the macroligand of 2,6-bis(1-PNIPAM-1,2,3-triazol-4-yl)pyridine (4) and the chelating reaction of RuCl3 with 4 to afford 5. The thermoresponsive properties of the resulting polymers were investigated using a UV-vis spectrophotometer by measuring the optical transmittance of the polymer solution with varying solution temperature and the cloud point (Tc) at 50% transmittance intensity in order to assess their thermoresponsive properties. The detailed thermoresponsive properties of these polymers, including the effects of the polymer terminal and core linkage and constituents of the four-arm star-shaped PNIPAMs on the Tc, are significantly described in the later part of this study.

Projection of future changes in the frequency of intense tropical cyclones

Recent modeling studies have consistently shown that the global frequency of tropical cyclones will decrease but that of very intense tropical cyclones may increase in the future warmer climate. It has been noted, however, that the uncertainty in the projected changes in the frequency of very intense tropical cyclones, particularly the changes in the regional frequency, is very large. Here we present a projection of the changes in the frequency of intense tropical cyclones estimated by a statistical downscaling of ensemble of many high-resolution global model experiments. The results indicate that the changes in the frequency of very intense (category 4 and 5) tropical cyclones are not uniform on the globe. The frequency will increase in most regions but decrease in the south western part of Northwest Pacific, the South Pacific, and eastern part of the South Indian Ocean.

More tropical cyclones in a cooler climate

Recent review papers reported that many high-resolution global climate models consistently projected a reduction of global tropical cyclone (TC) frequency in a future warmer climate, although the mechanism of the reduction is not yet fully understood. Here we present a result of 4K-cooler climate experiment. The global TC frequency significantly increases in the 4K-cooler climate compared to the present climate. This is consistent with a significant decrease in TC frequency in the 4K-warmer climate. For the mechanism of TC frequency reduction in a warmer climate, upward mass flux hypothesis and saturation deficit hypothesis have been proposed. The result of the 4K-cooler climate experiment is consistent with these two hypotheses. One very interesting point is that the experiment has clearly shown that TC genesis is possible at sea surface temperature (SST) well below 26°C which has been considered as the lowest SST limit for TC genesis.

The resolution sensitivity of the Asian summer monsoon and its inter-model comparison between MRI-AGCM and MetUM

In this study, we compare the resolution sensitivity of the Asian Summer Monsoon (ASM) in two Atmospheric General Circulation Models (AGCMs): the MRI-AGCM and the MetUM. We analyze the MetUM at three different resolutions, N96 (approximately 200-km mesh on the equator), N216 (90-km mesh) and N512 (40-km mesh), and the MRI-AGCM at TL95 (approximately 180-km mesh on the equator), TL319 (60-km mesh), and TL959 (20-km mesh). The MRI-AGCM and the MetUM both show decreasing precipitation over the western Pacific with increasing resolution, but their precipitation responses differ over the Indian Ocean. In MRI-AGCM, a large precipitation increase appears off the equator (5–20°N). In MetUM, this off-equatorial precipitation increase is less significant and precipitation decreases over the equator. Moisture budget analysis demonstrates that a changing in moisture flux convergence at higher resolution is related to the precipitation response. Orographic effects, intra-seasonal variability and the representation of the meridional thermal gradient are explored as possible causes of the resolution sensitivity. Both high-resolution AGCMs (TL959 and N512) can represent steep topography, which anchors the rainfall pattern over south Asia and the Maritime Continent. In MRI-AGCM, representation of low pressure systems in TL959 also contributes to the rainfall pattern. Furthermore, the seasonal evolution of the meridional thermal gradient appears to be more accurate at higher resolution, particularly in the MRI-AGCM. These findings emphasize that the impact of resolution is only robust across the two AGCMs for some features of the ASM, and highlights the importance of multi-model studies of GCM resolution sensitivity.

The representation of solar cycle signals in stratospheric ozone. Part II: Analysis of global models

Monthly and zonal mean coefficients for the 11 year solar cycle effect on stratospheric ozone derived from the CMIP6 ozone dataset. The coefficients are provided on a 3-D (latitude-pressure-month) grid and are derived using multiple linear regression of ozone against either: (1) the F10.7cm solar radio flux (cmip6_solar-o3_coeffs_per_SFU.nc); and (2) the 200-320 nm integrated spectral solar irradiance (cmip6_solar-o3_coeffs_per_Wm-2.nc) for the period 1960-2011. The coefficients are provided in terms of both % and mol mol-1 of ozone change. Also included are p-values for the ozone coefficients as a function of latitude-pressure-month. The dataset is provided in NetCDF format.

Synthesis of multifunctional poly(1-pyrenemethyl methacrylate)-b-poly(N-isopropylacrylamide)-b-poly(N-methylolacrylamide)s and their electrospun nanofibers for metal ion sensory applications

We report the synthesis and characterization of multifunctional triblock copolymers, poly(1-pyrenemethylmethacrylate)-block-poly(N-isopropylacrylamide)-block-poly(N-methylolacrylamide) (PPy-b-PNIPAAm-b-PNMA), and their electrospun (ES) nanofibers for temperature or metal-ion sensing. The triblock copolymers are composed of fluorescent and metal-ion-sensitive PPy, thermoresponsive PNIPAAm, and chemically crosslinkable PNMA segments. Non-crosslinked ES nanofibers are initially prepared using the aforementioned PPy-b-PNIPAAm-b-PNMA triblock copolymers followed by thermal crosslinking. It is found that ES nanofibers prepared from PPy-b-PNIPAAm-b-PNMA can self-assemble to form nano-scale spherical aggregates with PNMA located at the core, PNIPAAm at the center layer, and PPy at the shell. This self-assembly characteristic therefore induces a strong excimer emission between the pyrenyl moieties. The crosslinking process between PNMA blocks is then implemented to stabilize the ES nanofibers since the non-crosslinked ones are metastable objects. The resulting crosslinked nanofibers exhibit a predominant wettability and dimension stability under aqueous states, and can perform a detectable photoluminescence transition at different temperatures or toward an Fe3+ ion. In contrast to their counterpart drop-cast film, ES nanofibers with a high surface/volume ratio have obviously higher sensing ability toward thermal stimuli and metal ions, and are expected to be applied as multifunctional sensory devices.

Future Changes in the Ozone Quasi-Biennial Oscillation with Increasing GHGs and Ozone Recovery in CCMI Simulations

AbstractThe future quasi-biennial oscillation (QBO) in ozone in the equatorial stratosphere is examined by analyzing transient climate simulations due to increasing greenhouse gases (GHGs) and decreasing ozone-depleting substances under the auspices of the Chemistry–Climate Model Initiative. The future (1960–2100) and historical (1979–2010) simulations are conducted with the Meteorological Research Institute Earth System Model. Three climate periods, 1960–85 (past), 1990–2020 (present), and 2040–70 (future) are selected, corresponding to the periods before, during, and after ozone depletion. The future ozone QBO is characterized by increases in amplitude by 15%–30% at 5–10 hPa and decreases by 20%–30% at 40 hPa, compared with the past and present climates; the future and present ozone QBOs increase in amplitude by up to 60% at 70 hPa, compared with the past climate. The increased amplitude at 5–10 hPa suggests that the temperature-dependent photochemistry plays an important role in the enhanced future ozo...

Assessment of the Surgical Correction of Epiglottic Entrapment in Racing Horses.

喉頭蓋エントラップメント (EE) を発症した競走馬4頭に対し, 高周波焼灼装置, EE用鉤状カッターを用いた外科的療法を試みた。まず1頭においては, 鎮静下での高周波焼灼法による披裂喉頭蓋ヒダの切開をおこなったが, 嚥下反射を完全に抑制することが出来ず, 不十分なものであったため, 全身麻酔下でのEE用鉤状カッターによる切開を試みた。また他の3症例では, 前例での経過を考慮し, EE用鉤状カッターによる切開を試みた。これらの結果, 術後の経過は良好であり, 短期間の休養のみでトレーニングに供することができた。以上より, 競走馬に発症したEEに対しては, 休養期間の短さや, 術後の患部の経過等から, EE用鉤状カッターによる外科的療法が有効であることが示唆された。