A dataset of continental river discharge based on JRA-55 for use in a global ocean circulation model     

Tatsuo Suzuki  Dai Yamazaki  Hiroyuki Tsujino  Yoshiki Komuro  Hideyuki Nakano  Shogo Urakawa 《Journal of Oceanography》2018,74(4):421-429

A dataset of historical river discharge into oceans was created using the CaMa-Flood global river routing model and adjusted runoff from the land component of JRA-55. The major rivers were well resolved with a 0.25° horizontal resolution. The total runoff on each drainage basin exhibits a distinctive bias on decadal time scales. The input runoff data were modified using 5-year low-pass-filtered multiplicative factors to fit the annual mean climatology and decadal variations in the reference dataset. The model incorporated data from 1958 to 2016. The yearly and seasonal variations of the major rivers are well represented by the model.  相似文献   

Damage sequence and safety margin assessment of expansion joints by shake table testing     

Yu Otsuki  Masahiro Kurata  Konstantinos A. Skalomenos  Yoshiki Ikeda 《地震工程与结构动力学》2019,48(1):3-26

The performance of nonstructural components has attracted attention, and previous large earthquakes have resulted in widespread damage to expansion joints. In contrast to the main structural components, for which ductility beyond the design tolerance is ensured, the safety margin of nonstructural components classified as the product of mechanical engineering, such as expansion joints, is uncertain. This paper investigates the damage sequence and safety margin of expansion joints through shake table testing. The expansion joints were installed to connect 2 rigid steel frames with short and long natural periods. Four commonly used types, high-performance and standard-performance floor and wall expansion joints, were tested. Seven damage patterns of the 4 expansion joints were observed, and most of the damage patterns were considered displacement dependent. The damage mechanisms and relative displacements at the moment of damage were identified by using strain gauges attached near collision and damage locations. The high-performance expansion joints showed only minor damage beyond the design motion range, whereas the standard-performance expansion joints exhibited minor damage below the design motion range and failure at the design motion range or slightly beyond. For each damage state, repair information was obtained through a questionnaire to an expansion joint manufacturer, and the sum of the initial cost and repair cost for high-performance and standard-performance expansion joints was compared. The results will be useful for the selection of expansion joints in the design process.  相似文献   

Forecast of Tsunamis from the Japan–Kuril–Kamchatka Source Region     

Yoshiki Yamazaki  Yong Wei  Kwok Fai Cheung  George D. Curtis 《Natural Hazards》2006,38(3):411-435

This paper describes an investigation of the subfault distribution along the Japan–Kuril–Kamchatka subduction zone for the implementation of a far-field tsunami forecast algorithm. Analyses of seismic data from 1900 to 2000 define the subduction zone, which in turn is divided into 222 subfaults based on the fault characteristics. For unit slip of the subfaults, a linear long-wave model generates a database of mareograms at water-level stations along the subduction zone and at warning points in the North Pacific. When a tsunami occurs, an inverse algorithm determines the slip distribution from near-source water-level records and predicts the waveforms at the warning points using the pre-computed mareograms. A jackknife resampling scheme uses combinations of input water-level records to provide a series of waveform predictions for the computation of the confidence-interval bounds. The inverse algorithm is applied to hindcast two major tsunamis generated from the Japan–Kuril–Kamchatka source and the computed tsunami heights show good agreement with recorded water-level data.  相似文献   

A photometric study of poor clusters of galaxies     

Yamagata  Tomohiko  Maehara  Hideo 《Astrophysics and Space Science》1986,118(1-2):459-462

Sixteen poor clusters of galaxies with suspected cD galaxies are studied usingV-band photographs taken with the 105 cm Kiso Schmidt telescope. Galaxian images were automatically detected using an image detection software developed for the present study. It is found from the luminosity functions that the richness of the clusters are well correlated with the optical properties of central galaxies and the X-ray luminosities of the clusters.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.  相似文献   

Morphodynamics of deltas under the influence of humans   总被引：8，自引：0，他引：8  

James P.M. Syvitski  Yoshiki Saito   《Global and Planetary Change》2007,57(3-4):261-282

A consistent database was established to characterize key environmental factors known to control delta morphology. The database includes the location, basin morphology, fluvial and sediment discharge to the deltas, delta morphology, ocean energy, and shelf depth reached by the sub-aqueous delta. Fifty-one deltas were selected to cover the global parameter range of rivers entering all major oceans and coastal seas. Seasonal satellite images of the deltas were processed (IKONOS, SPOT, LANDSAT, and MODIS). Predictive statistical relationships were obtained, suitable for hypothesis testing or to constrain/verify numerical models used to simulate the evolution of coastal systems. The area of a delta is best predicted from average discharge, the total sediment load feeding the delta, and the offshore accommodation space. The gradient of a delta plain, measured from the apex of the delta to the coast along the main channel, is best predicted with a ratio of sediment supply to sediment retention, sediment concentration used as a proxy of delta plain sedimentation, and mean water discharge. Widths of distributary channels form a lognormal distribution, with the cumulative width of the river mouths directly related to the maximum discharge, tidal and wave energy. The grain size of topset deposits scales with the river length. Hundreds of millions of people occupy deltas and human engineering is now a major influence on the growth and evolution of many deltas, through control of the flow path of distributary channels, and mitigation of the seasonal flood wave with concomitant change in the delivery of sediment load. More and more deltas are moving away from their pre-Anthropocene morphology, as influenced by pristine sediment supply and sediment dispersal.  相似文献   

El Niño Modoki connection to extremely-low streamflow of the Paranaíba River in Brazil     

Netrananda Sahu  Swadhin K. Behera  J. V. Ratnam  Roberto Valmir Da Silva  Pradipta Parhi  Weili Duan  Kaoru Takara  R. B. Singh  Toshio Yamagata 《Climate Dynamics》2014,42(5-6):1509-1516

Extremely-low discharge events of the Paranaíba River basin during the austral summer season (December–February, DJF), are found to be associated with the Pacific sea surface temperature anomalies resembling the recently identified El Niño Modoki phenomenon. Extreme discharge events are identified based on their persistent flow for 7 days and more after taking retention time into consideration. Ninety percent of the extremely low discharge events during peak streamflow seasons of DJF, are found to occur during the El Niño Modoki years. A diagnostics study of atmospheric anomalies has shown a clear connection between the modified Walker circulation, associated with the El Niño Modoki, and the precipitation anomalies over the Paranaíba River basin. The climate variations have direct relationship with the rainfall. Streamflow variations are considered as the surrogates to rainfalls. Thus, El Niño Modoki phase is important component to understand and predict the streamflow variations in the Paranaíba River basin.  相似文献   

Intensification of decadal and multi-decadal sea level variability in the western tropical Pacific during recent decades   总被引：1，自引：0，他引：1  

Weiqing Han  Gerald A. Meehl  Aixue Hu  Michael A. Alexander  Toshio Yamagata  Dongliang Yuan  Masayoshi Ishii  Philip Pegion  Jian Zheng  Benjamin D. Hamlington  Xiao-Wei Quan  Robert R. Leben 《Climate Dynamics》2014,43(5-6):1357-1379

Previous studies have linked the rapid sea level rise (SLR) in the western tropical Pacific (WTP) since the early 1990s to the Pacific decadal climate modes, notably the Pacific Decadal Oscillation in the north Pacific or Interdecadal Pacific Oscillation (IPO) considering its basin wide signature. Here, the authors investigate the changing patterns of decadal (10–20 years) and multidecadal (>20 years) sea level variability (global mean SLR removed) in the Pacific associated with the IPO, by analyzing satellite and in situ observations, together with reconstructed and reanalysis products, and performing ocean and atmosphere model experiments. Robust intensification is detected for both decadal and multidecadal sea level variability in the WTP since the early 1990s. The IPO intensity, however, did not increase and thus cannot explain the faster SLR. The observed, accelerated WTP SLR results from the combined effects of Indian Ocean and WTP warming and central-eastern tropical Pacific cooling associated with the IPO cold transition. The warm Indian Ocean acts in concert with the warm WTP and cold central-eastern tropical Pacific to drive intensified easterlies and negative Ekman pumping velocity in western-central tropical Pacific, thereby enhancing the western tropical Pacific SLR. On decadal timescales, the intensified sea level variability since the late 1980s or early 1990s results from the “out of phase” relationship of sea surface temperature anomalies between the Indian and central-eastern tropical Pacific since 1985, which produces “in phase” effects on the WTP sea level variability.  相似文献   

On the Ningaloo Niño/Niña     

Takahito Kataoka  Tomoki Tozuka  Swadhin Behera  Toshio Yamagata 《Climate Dynamics》2014,43(5-6):1463-1482

Using both observational and reanalysis data, evolution processes of a regional climate phenomenon off Western Australia named recently “Ningaloo Niño (Niña)” are studied in detail. It is also shown that the Ningaloo Niño (Niña) has significant impacts on the precipitation over Australia. The Ningaloo Niño (Niña), which is associated with positive (negative) sea surface temperature (SST) anomalies and atmospheric anomalies off the western coast of Australia, peaks during austral summer and is classified into two types based on the difference in the evolution process. The first type called a locally amplified mode develops through an intrinsic unstable air–sea interaction off the western coast of Australia; an anomalous cyclone (anticyclone) generated by positive (negative) SST anomalies forces northerly (southerly) alongshore wind anomalies, which induce coastal downwelling (upwelling) anomalies, and enhance the positive (negative) SST anomalies further. The second type called a non-locally amplified mode is associated with coastally trapped waves originating in either the western tropical Pacific, mostly related to El Niño/Southern Oscillation, or the northern coast of Australia. Positive (negative) SST anomalies in both modes are associated with an anomalous low (high) off the western coast of Australia. The sea level pressure (SLP) anomalies in the locally amplified mode are regionally confined with a cell-like pattern and produce a sharp offshore pressure gradient along the western coast of Australia, whereas those in the non-locally amplified mode tend to show a zonally elongated pattern. The difference is found to be related to conditions of the continental SLP modulated by the Australian summer monsoon and/or the Southern Annular Mode.  相似文献   

An emission pathway for stabilization at 6?Wm?2 radiative forcing   总被引：1，自引：0，他引：1  

Toshihiko Masui  Kenichi Matsumoto  Yasuaki Hijioka  Tsuguki Kinoshita  Toru Nozawa  Sawako Ishiwatari  Etsushi Kato  P. R. Shukla  Yoshiki Yamagata  Mikiko Kainuma 《Climatic change》2011,109(1-2):59-76

Representative Concentration Pathway 6.0 (RCP6) is a pathway that describes trends in long-term, global emissions of greenhouse gases (GHGs), short-lived species, and land-use/land-cover change leading to a stabilisation of radiative forcing at 6.0 Watts per square meter (Wm^?2) in the year 2100 without exceeding that value in prior years. Simulated with the Asia-Pacific Integrated Model (AIM), GHG emissions of RCP6 peak around 2060 and then decline through the rest of the century. The energy intensity improvement rates changes from 0.9% per year to 1.5% per year around 2060. Emissions are assumed to be reduced cost-effectively in any period through a global market for emissions permits. The exchange of CO₂ between the atmosphere and terrestrial ecosystem through photosynthesis and respiration are estimated with the ecosystem model. The regional emissions, except CO₂ and N₂O, are downscaled to facilitate transfer to climate models.  相似文献   

Anomalous summer climate in China influenced by the tropical Indo-Pacific Oceans     

Hengyi Weng  Guoxiong Wu  Yimin Liu  Swadhin K. Behera  Toshio Yamagata 《Climate Dynamics》2011,36(3-4):769-782

Possible influences of three coupled ocean–atmosphere phenomena in the Indo-Pacific Oceans, El Niño, El Niño Modoki and the Indian Ocean Dipole (IOD), on summer climate in China are studied based on data analysis for the summers of 1951–2007. Partial correlation/regression analysis is used to find the influence paths through the related anomalous mid- and low-level tropospheric circulations over the oceanic region and East Eurasia, including the western North Pacific summer monsoon (WNPSM). Among the three phenomena, El Niño Modoki has the strongest relationship with the WNPSM. When two or three phenomena coexist with either positive or negative phase, the influences exerted by one phenomenon on summer climate in different regions of China may be enhanced or weakened by other phenomena. In 1994 when both El Niño Modoki and IOD are prominent without El Niño, a strong WNPSM is associated with severe flooding in southern China and severe drought in the Yangtze River Valley (YRV). The 500 hPa high systems over China are responsible for heat waves in most parts of China. In 1983 when a strong negative phase of El Niño Modoki is accompanied by moderate El Niño and IOD, a weak WNPSM is associated with severe flooding in the YRV and severe drought in southern China. The 500 hPa low systems over China are responsible for the cold summer in the YRV and northeastern China. For rainfall, the influence path seems largely through the low-level tropospheric circulations including the WNPSM. For temperature, the influence path seems largely through the mid-level tropospheric circulations over East Eurasia/western North Pacific Ocean.  相似文献