排序方式： 共有30条查询结果，搜索用时 78 毫秒
21.
Tokuta Yokohata James D. Annan Matthew Collins Charles S. Jackson Hideo Shiogama Masahiro Watanabe Seita Emori Masakazu Yoshimori Manabu Abe Mark J. Webb Julia C. Hargreaves 《Climate Dynamics》2013,41(9-10):2745-2763
We investigate the performance of the newest generation multi-model ensemble (MME) from the Coupled Model Intercomparison Project (CMIP5). We compare the ensemble to the previous generation models (CMIP3) as well as several single model ensembles (SMEs), which are constructed by varying components of single models. These SMEs range from ensembles where parameter uncertainties are sampled (perturbed physics ensembles) through to an ensemble where a number of the physical schemes are switched (multi-physics ensemble). We focus on assessing reliability against present-day climatology with rank histograms, but also investigate the effective degrees of freedom (EDoF) of the fields of variables which makes the statistical test of reliability more rigorous, and consider the distances between the observation and ensemble members. We find that the features of the CMIP5 rank histograms, of general reliability on broad scales, are consistent with those of CMIP3, suggesting a similar level of performance for present-day climatology. The spread of MMEs tends towards being “over-dispersed” rather than “under-dispersed”. In general, the SMEs examined tend towards insufficient dispersion and the rank histogram analysis identifies them as being statistically distinguishable from many of the observations. The EDoFs of the MMEs are generally greater than those of SMEs, suggesting that structural changes lead to a characteristically richer range of model behaviours than is obtained with parametric/physical-scheme-switching ensembles. For distance measures, the observations and models ensemble members are similarly spaced from each other for MMEs, whereas for the SMEs, the observations are generally well outside the ensemble. We suggest that multi-model ensembles should represent an important component of uncertainty analysis. 相似文献
22.
23.
24.
Solar Physics - Possible solar neutron emission associated with five SMM gamma-ray events on 7 June 1980, 21 June 1980, 6 November 1980, 26 November 1982 and 25 April 1984 was found from analysis... 相似文献
25.
Glacial termination: sensitivity to orbital and CO2 forcing in a coupled climate system model 总被引：1，自引：0，他引：1
To study glacial termination and related feedback mechanisms, a continental ice dynamics model is globally and asynchronously
coupled to a physical climate (atmosphere-ocean-sea ice) model. The model performs well under present-day, 11 kaBP (thousand
years before present) and 21 kaBP perpetual forcing. To address the ice-sheet response under the effects of both perpetual
orbital and CO2 forcing, sensitivity experiments are conducted with two different orbital configurations (11 kaBP and 21 kaBP) and two different
atmospheric CO2 concentrations (200 ppmv and 280 ppmv). This study reveals that, although both orbital and CO2 forcing have an impact on ice-sheet maintenance and deglacial processes, and although neither acting alone is sufficient
to lead to complete deglaciation, orbital forcing seems to be more important. The CO2 forcing has a large impact on climate, not uniformly or zonally over the globe, but concentrated over the continents adjacent
to the North Atlantic. The effect of increased CO2 (from 200 ppmv to 280 ppmv) on surface air temperature has its peak there in winter associated with a reduction in sea-ice
extent in the northern North Atlantic. These changes are accompanied by an enhancement in the intensity of the meridional
overturning and poleward ocean heat transport in the North Atlantic. On the other hand, the effect of orbital forcing (from
21 kaBP to 11 kaBP) has its peak in summer. Since the summer temperature, rather than winter temperature, is found to be dominant
for the ice-sheet mass balance, orbital forcing has a larger effect than CO2 forcing in deglaciation. Warm winter sea surface temperature arising from increased CO2 during the deglaciation contributes to ice-sheet nourishment (negative feedback for ice-sheet retreat) through slightly enhanced
precipitation. However, the precipitation effect is totally overwhelmed by the temperature effect. Our results suggest that
the last deglaciation was initiated through increasing summer insolation with CO2 providing a powerful feedback.
Received: 22 February 2000 / Accepted: 17 September 2000 相似文献
26.
Akira Yoshimori 《Journal of Oceanography》1993,49(5):521-533
Semi-geostrophic dynamics of jets are studied using a potential vorticity front in an equivalent barotropic model. Meandering processes of the front are examined in the thin-jet limit on a -plane by a curvilinear coordinate system. For calculated along-front velocity fields, asymmetrical profiles are caused by meandering. This asymmetry of the velocity profile is enhanced as the Rossby number becomes large. Using the along-front velocity fields, the normal velocity of front is expressed so that the Rossby number is explicitly included. This expression can be rewritten in the form of the mKdV equation. 相似文献
27.
Electrical conductivity anomalies in the earth 总被引：1，自引：0，他引：1
Yoshimori Honkura 《Surveys in Geophysics》1978,3(3):225-253
Anomalies of short-period geomagnetic variations have been found in various regions over the world. It is known that such anomalies arise from electromagnetic induction within an electrical conductivity anomaly or from local perturbation of induced electric currents by a conductivity anomaly. In order to investigate a regional electric state in the Earth, conductivity anomaly (CA) studies based on anomalous behaviors of geomagnetic variations have been extensively undertaken, as well as studies based on magnetotelluries in which induced currents are directly used.Some of the geomagnetic variation anomalies, however, turned out to be caused by surface conductors, such as sea water and sediments. Anomalies of this sort have been intensively studied and classified into coast, island, peninsula, and strait effects in the case of sea effects. Three-dimensional conduction or channelling of induced electric currents is sometimes observed in the cases of sediments and some crustal conductivity anomalies. However, anomalies of such surface origins often provide some information of the underground conductivity structure.Electrical conductivity anomalies can be classified into two types: anomalies originating in the crust and in the upper mantle. Many of crustal anomalies are well correlated with metamorphic belts, fracture zones, and hydrated layers, and magnetic and gravity anomalies are also often found over the conductivity anomalies. Most of mantle anomalies have been interpreted mainly in terms of high temperature and partial melting, since conductivity anomalies coincide well with anomalies in heat flow and seismic wave velocities. 相似文献
28.
Masakazu Yoshimori Christoph C. Raible Thomas F. Stocker Manuel Renold 《Climate Dynamics》2006,27(5):493-513
An increasing number of proxy records, which are related to changes in the hydrological cycle, have been collected for climate reconstructions of the last millennium. There has been, however, little attempt to test climate models with such proxy records or to interpret proxy records using climate model simulations. In the present study, we analyze the hydrological changes between three different types of experiments: a present-day control, a perpetual AD 1640, and an ensemble of six transient Maunder Minimum (AD 1640–1715) simulations. Atmospheric moisture transport is investigated in terms of contributions of specific humidity and circulation changes. The study points out the importance of the specific humidity contribution to changes in moisture transport reflected in hydrological proxy records. The moisture budget of the western tropical Pacific is also investigated to aid the interpretation of a proxy record in this specific region. The present-day freshening of the western tropical Pacific, compared to the Maunder Minimum, is explained by the increased zonal moisture transport via trade winds, mainly due to the increased amount of atmospheric water vapor content in the warming world. Due to the existence of several uncertainty factors, such as forcing reconstructions, the link between the model simulations and proxy records is, however, not definitive, but the thermal contribution to hydrological proxy records is important and not limited to the Maunder Minimum period. 相似文献
29.
Yasuhiro Ishizaki Hideo Shiogama Seita Emori Tokuta Yokohata Toru Nozawa Tomoo Ogura Manabu Abe Masakazu Yoshimori Kiyoshi Takahashi 《Climatic change》2012,112(2):535-546
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. 相似文献
30.
Modeling of spring bloom in the western subarctic Pacific (off Japan) with observed vertical density structure 总被引：1，自引：0，他引：1
A. Yoshimori J. Ishizaka T. Kono H. Kasai H. Saito M. J. Kishi S. Taguchi 《Journal of Oceanography》1995,51(4):471-488
Effects of vertical stability on spring blooms of phytoplankton were investigated for the western subarctic Pacific ocean using a one-dimensional (depth) ecosystem model. In the model, vertical stability was expressed by diffusion constants calculated from observed density distribution. Dynamics of phytoplankton in blooms was calculated by the model using the vertical diffusion. Then, the calculated results were compared with the Coastal Zone Color Scanner (CZCS) data. The comparison shows that the shallow surface mixed layer causes early start days of spring blooms at inshore (northern) stations. In addition, spring blooms continue long at inshore (northern) stations since a water column has weak stability. This is because weak stability of a water column causes large nutrient supply from a deep layer and large diffusive transport of phytoplankton biomass from the subsurface maximum. 相似文献