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191.
A new cloud parameterization based on prognostic equations for the subgrid-scale fluctuations in temperature and total water
content is introduced for global climate models. The proposed scheme, called hybrid prognostic cloud (HPC) parameterization,
employs simple probability density functions (PDFs) to the horizontal subgrid-scale inhomogeneity, allowing them to vary in
shape in response to small-scale processes such as cumulus detrainment and turbulent mixing. Simple tests indicate that the
HPC scheme is highly favorable as compared to a diagnostic scheme in terms of the cloud fraction and cloud water content under
either uniform or non-uniform forcing. The relevance of the HPC scheme is investigated by implementing it in an atmospheric
component model of the climate model MIROC with a coarse resolution of T42. A comparison of the short-term integrations between
the T42 model and a global cloud resolving model (GCRM) reveals that the HPC scheme can reproduce, to a certain degree, the
subgrid-scale variance and skewness of temperature and total water content simulated in the GCRM. It is also found that the
HPC scheme significantly alters the climatological distributions in cloud cover, precipitation, and moisture, which are all
improved from the model using a conventional diagnostic cloud scheme. 相似文献
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195.
A three-dimensional formulation based on Green's functions of cylindrical loads in layered semi-infinite media is employed to investigate the dynamic behaviour of piles in homogeneous and non-homogeneous half spaces. The pile-soil-pile interaction taking place in pile groups is incorporated in the model. The results presented in this paper include the dynamic stiffnesses and dampings of single piles as well as those of representative 2 × 2 and 4 × 4 square pile groups in the soil media considered in this study. In addition, the distribution of forces applied on the pile cap among the individual piles in a group is investigated. 相似文献
196.
Norikatsu Akizawa Akira Miyake Yohei Igami Akira Tsuchiyama Hisashi Asanuma Tetsu Kogiso Shigeyuki Wakaki Tsuyoshi Ishikawa Shoji Arai Jiwon Eom Hodaka Kawahata Takahiro Aze Yusuke Yokoyama 《Island Arc》2021,30(1):e12423
Hydrothermal circulation beneath the spreading axis plays a significant role in the exchange of energy and mass between the solid Earth and the oceans. Deep-seated hydrothermal circulation down to the crust/mantle boundary in the fast-spreading axis has been introduced by a number of studies regarding geological investigations and numerical models. In order to assess a reaction between hydrothermal fluid and host rock around the crust/mantle boundary, we conducted bulk trace element and Sr isotope analyses with a series of in situ investigations for crustal anorthosite, a reaction product between hydrothermal fluid and gabbro in the lowermost crustal section along Wadi Fizh, northern Oman ophiolite. In addition, we conducted titanite U–Pb isotope analyses to evaluate timing of the crustal anorthosite formation in the framework of the evolutional process of the Oman ophiolite. We estimated the formation age of the crustal anorthosite at 97.5 Ma ± 5.0 Ma, overlapping with the timing of the crust formation in the paleo spreading axis. The crustal anorthosite shows high-Th/U ratio (~2.5) and high-initial 87Sr/86Sr ratio (0.7050) due to seawater-derived hydrothermal fluid ingress into the precursor gabbro. With using analytical technique of micro-excavation at cryo-temperature, we detected Cl from a few micrometer-sized inclusion of aqueous fluid and chromite grains. The solubility of Cr was enhanced by complexation reactions with Cl in the hydrothermal fluid. Regarding reconstructed three-dimensional mass distribution of the inclusion and chromite composition, maximum Cr content of parental fluid was estimated at ~69 000 μg/g. The exceptionally high-Cr content was achieved locally by leaking of fluid and synchronous chromite crystallization during fluid entrapment. Presence of the deep-seated hydrothermal circulation could be assigned to the segment end, where cold seawater penetrates into the lowermost crust and extract heat along widely spaced network-like fluid channel. 相似文献
197.
Noriyuki Matsunaga Hinako Fukushi Yoshikazu Nakada Toshihiko Tanabé Michael W. Feast John W. Menzies Yoshifusa Ita Shogo Nishiyama Daisuke Baba Takahiro Naoi Hidehiko Nakaya Takahiro Kawadu Akika Ishihara Daisuke Kato 《Monthly notices of the Royal Astronomical Society》2006,370(4):1979-1990
We report the result of our near-infrared observations ( JHK s ) for type II Cepheids (including possible RV Tau stars) in galactic globular clusters. We detected variations of 46 variables in 26 clusters (10 new discoveries in seven clusters) and present their light curves. Their periods range from 1.2 d to over 80 d. They show a well-defined period–luminosity relation at each wavelength. Two type II Cepheids in NGC 6441 also obey the relation if we assume the horizontal branch stars in NGC 6441 are as bright as those in metal-poor globular clusters in spite of the high metallicity of the cluster. This result supports the high luminosity which has been suggested for the RR Lyr variables in this cluster. The period–luminosity relation can be reproduced using the pulsation equation assuming that all the stars have the same mass. Cluster RR Lyr variables were found to lie on an extrapolation of the period–luminosity relation. These results provide important constraints on the parameters of the variable stars.
Using Two Micron All-Sky Survey (2MASS) data, we show that the type II Cepheids in the Large Magellanic Cloud (LMC) fit our period–luminosity relation within the expected scatter at the shorter periods. However, at long periods ( P > 40 d, i.e. in the RV Tau star range) the LMC field variables are brighter by about one magnitude than those of similar periods in galactic globular clusters. The long-period cluster stars also differ from both these LMC stars and galactic field RV Tau stars in a colour–colour diagram. The reasons for these differences are discussed. 相似文献
Using Two Micron All-Sky Survey (2MASS) data, we show that the type II Cepheids in the Large Magellanic Cloud (LMC) fit our period–luminosity relation within the expected scatter at the shorter periods. However, at long periods ( P > 40 d, i.e. in the RV Tau star range) the LMC field variables are brighter by about one magnitude than those of similar periods in galactic globular clusters. The long-period cluster stars also differ from both these LMC stars and galactic field RV Tau stars in a colour–colour diagram. The reasons for these differences are discussed. 相似文献
198.
Takahiro Kudoh Ryoji Matsumoto Kazunari Shibata 《Astrophysics and Space Science》2003,287(1-4):99-102
We present the MHD simulation including accretion flows in disks, acceleration of outflows from disks, and collimation of the outflows self-consistently. Although it was considered that this kind of simulations only shows the transient phenomena of jets, we found that the outflow and accretion flow reached a quasi-steady state by performing a long-term calculation in a large calculation region. Though the final stage is not exactly the steady state, the acceleration and collimation mechanisms of the outflow were the same as those of the steady theory. The scale of the calculation is approaching to the scale that was observed by the VLBI technique, which provides the current highest resolution for YSO jets. 相似文献
199.