A Late Winter Hydrography in Hidaka Bay, South of Hokkaido, Japan     

Manabu Shimizu  Yutaka Isoda  Kazumi Baba 《Journal of Oceanography》2001,57(4):385-395

Hydrographic observations in Hidaka Bay, south of Hokkaido, Japan were carried out in late winter 1996 and 1997 to examine the spatial distributions and circulation features of two different water masses, i.e., Coastal Oyashio Water (COW) and Tsugaru Warm Water (TWW), and their modifications. It is known that COW is mostly composed of cold and low-salinity water of the melted drift ice coming from the Okhotsk Sea and flows into Hidaka Bay from winter to spring and TWW with high-salinity continuously supplies from the Tsugaru Strait to the North Pacific. Cold surface mixed layers (<26.2σ_θ, 0–100 m depth) were found mainly over the shelf slope, confirming that anti-clockwise flow of COW was formed. TWW was relatively high in salinity and low in potential vorticity, and had some patch-like water masses with a temperature and salinity maximum in the limited area in the further offshore at the deeper density levels of 26.6–26.8σ_θ. The fine structure of vertical temperature and salinity profiles appeared between TWW and COW is an indication of enhanced vertical mixing (double-diffusive mixing), as inferred from the estimated Turner angles. At a mouth of the Tsugaru Strait in late winter 1997, a significant thermohaline front between TWW and the modified COW was formed and a main path of TWW spreaded south along the Sanriku coast, probably as the bottom controlled flow. Hence, the patch-like TWW observed in late winter is isolated from the Tsugaru Warm Current and then rapidly modified due to a diapycnal mixing. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Pi-SAR极化数据与K分布指数估算森林生物量与实验验证   总被引：1，自引：0，他引：1  

王海鹏  金亚秋  大内和夫  渡边学  岛田政信 《遥感学报》2008,12(3):477-482

用2002年和2003年日本Pi-SAR全极化数据,研究日本北海道苫小牧森林地区的森林生物量.雷达后向散射系数随森林生物量的增大而增大并迅速达到饱和,L波段雷达数据饱和点约为40t/hm2,X波段仅约为20t/hm2.在SAR数据统计分布中,K分布的指数参数在饱和点以上仍随生物量的增大而增大,并且HV极化方式时相关性最高.根据交叉极化数据K分布的指数参数与森林生物量的关系,本文估算了23个观测点的森林生物量,结果表明平均准确率为85%.因此该算法可以作为一种新的估算森林生物量的手段.  相似文献   

The relationship between the isotopic content of precipitation and the precipitation amount in tropical regions     

Naoyuki Kurita  Kimpei Ichiyanagi  Jun Matsumoto  Manabu D. Yamanaka  Tetsuo Ohata   《Journal of Geochemical Exploration》2009,102(3):113

General circulation models (GCMs) fitted with stable isotope schemes are widely used to interpret the isotope–climate relationship. However, previous studies have found that the spatiotemporal isotope/precipitation correlation simulated by GCMs is stronger and more widespread than the observed value. To understand the reason for this failure, we investigated the factors influencing the empirically well-known isotope/precipitation relationship, or precipitation amount effect, in the tropics using newly obtained daily precipitation isotope monitoring data over Asia. As in previous studies, we found an apparent correlation between the long-term monthly mean isotopic content and the corresponding precipitation amount (local precipitation) observed at sub-tropical island stations. Furthermore, on a monthly timescale, the isotopic variability of precipitation for these stations was more clearly related to the regional precipitation amount than to local precipitation. This correlation of isotopic content with the regional precipitation amount was observed at the equatorial (Maritime Continent) stations. For these stations, isotope/local precipitation relationships only appeared over longer timescales, with different regression line slopes at each station. However, at the coastal stations, there was a strong linear relationship between the monthly mean isotopic content and corresponding regional precipitation, and regression line slopes were spatially uniform. For the two sub-tropical terrestrial (Indochina Peninsula) stations, the isotopic minimum appeared without any relationship to rainfall amount but usually occurred at the leeward station during the rainy season. These results suggest that the isotopic variations of precipitation did not depend on the ’local’ rain-out history but on the rain-out process in the surrounding region. However, local rainfall events were associated not only with large-scale disturbances but also with regional circulation. Thus, the scale difference of controlling factors between local rainfall amount and isotopic value results in the weakening of the rainfall amount effect at the observation site and in the discrepancy between GCM simulations and observations. This finding suggests that regional precipitation–isotope relationships should be compared with GCM results. Additionally, because the isotope signal reflects the rain-out history at a regional scale, evaluation of the isotopic field using isotopic GCMs will be useful not only to reconstruct paleoclimate conditions but also to examine how GCMs can reproduce real atmospheric circulation over the tropics.  相似文献   

Grain-scale iron isotopic distribution of pyrite from Precambrian shallow marine carbonate revealed by a femtosecond laser ablation multicollector ICP-MS technique: Possible proxy for the redox state of ancient seawater     

Manabu Nishizawa  Hiroki Yamamoto  Subaru Tsuruoka  Yusuke Sawaki  Yoshiaki Kon  Tsuyoshi Komiya  Takafumi Hirata 《Geochimica et cosmochimica acta》2010,74(9):2760-8899

The redox state of Precambrian shallow seas has been linked with material cycle and evolution of the photosynthesis-based ecosystem. Iron is a redox-sensitive element and exists as a soluble Fe(II) species or insoluble Fe(III) species on Earth’s surface. Previous studies have shown that the iron isotopic ratio of marine sedimentary minerals is useful for understanding the ocean redox state, although the redox state of the Archean shallow sea is poorly known. This is partly because the conventional bulk isotope analytical technique has often been used, wherein the iron isotopic record may be dampened by the presence of isotopically different iron-bearing minerals within the same sample. Here we report a microscale iron isotopic ratio of individual pyrite grains in shallow marine stromatolitic carbonates over geological time using a newly developed, near-infrared femtosecond laser ablation multicollector ICP-MS technique (NIR-fs-LA-MC-ICP-MS).We have determined that the grain-scale iron isotopic distribution of pyrite from coeval samples shows a bimodal (2.7 and 2.3 Ga) or unimodal pattern (2.9, 2.6, and 0.7 Ga). In particular, pyrite from the 2.7 Ga Fortescue Group shows a unique bimodal distribution with highly positive (+1.0‰ defined as Type 1) and negative δ⁵⁶Fe values (−1.8‰ defined as Type 2). Type 1 and 2 pyrites occasionally occur within different siliceous layers in the same rock specimen. Layer-scale iron isotopic heterogeneity indicates that the iron isotopic ratios of the two types of pyrite are not homogenized by diagenesis after deposition. Some cubic pyrites have a core with a positive δ⁵⁶Fe value (1‰) and a rim with a crustal δ⁵⁶Fe value (0‰). The observed isotopic zoning suggests that the positive δ⁵⁶Fe value is a primary signature at the time of stromatolite formation, while secondary pyrite precipitated during diagenesis.The positive δ⁵⁶Fe value of Type 1 and the large iron isotopic difference between Type 1 and 2 (2.8‰.) suggest partial Fe(II) oxidation in the 2.7-Ga shallow sea, i.e., pyritization of ⁵⁶Fe-enriched ferric oxyhydroxide (Type 1) and ⁵⁶Fe depleted Fe²⁺aq in seawater (Type 2). Type 2 pyrite was probably not produced by microbial iron redox cycling during diagenesis because this scenario requires a higher abundance of pyrite with δ⁵⁶Fe of 0‰ than of −1.8‰. Consequently, the degree of Fe(II) oxidation in the 2.7-Ga shallow sea can be estimated by a Fe²⁺aq steady-state model. The model calculation shows that half the Fe²⁺aq influx was oxidized in the seawater. This implies that O₂ produced by photosynthesis would have been completely consumed by oxidation of the Fe²⁺aq influx. Grain-scale iron isotopic distribution of pyrite could be a useful index for reconstructing the redox state of the Archean shallow sea.  相似文献   

A New Aerodynamic Parametrization for Real Urban Surfaces   总被引：7，自引：5，他引：2  

Manabu Kanda  Atsushi Inagaki  Takashi Miyamoto  Micha Gryschka  Siegfried Raasch 《Boundary-Layer Meteorology》2013,148(2):357-377

This study conducted large-eddy simulations (LES) of fully developed turbulent flow within and above explicitly resolved buildings in Tokyo and Nagoya, Japan. The more than 100 LES results, each covering a 1,000 $\times $ 1,000 m $^{2}$ area with 2-m resolution, provide a database of the horizontally-averaged turbulent statistics and surface drag corresponding to various urban morphologies. The vertical profiles of horizontally-averaged wind velocity mostly follow a logarithmic law even for districts with high-rise buildings, allowing estimates of aerodynamic parameters such as displacement height and roughness length using the von Karman constant $=$ 0.4. As an alternative derivation of the aerodynamic parameters, a regression of roughness length and variable Karman constant was also attempted, using a displacement height physically determined as the central height of drag action. Although both the regression methods worked, the former gives larger (smaller) values of displacement height (roughness length) by 20–25 % than the latter. The LES database clearly illustrates the essential difference in bulk flow properties between real urban surfaces and simplified arrays. The vertical profiles of horizontally-averaged momentum flux were influenced by the maximum building height and the standard deviation of building height, as well as conventional geometric parameters such as the average building height, frontal area index, and plane area index. On the basis of these investigations, a new aerodynamic parametrization of roughness length and displacement height in terms of the five geometric parameters described above was empirically proposed. The new parametrizations work well for both real urban morphologies and simplified model geometries.  相似文献   

Reliability and importance of structural diversity of climate model ensembles     

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   

Globe Anemo-radiometer     

Makoto Nakayoshi  Manabu Kanda  Richard de Dear 《Boundary-Layer Meteorology》2015,155(2):209-227

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THE BASTILLE DAY (14 JULY 2000) EVENT IN HISTORICAL LARGE SUN–EARTH CONNECTION EVENTS     

Watari  Shinichi  Kunitake  Manabu  Watanabe  Takashi 《Solar physics》2001,204(1-2):425-438

One of the large Sun–Earth connection events in solar cycle 23 occurred between 14 and 16 July 2000. Anomalies occurring on several satellites were reported in association with this event. Statistical study of extreme events is important not only for a view of space weather but for seeking ways to predict such kinds of large events. The Bastille Day event was characterized by a large flux (24 000 p.f.u. at its maximum) of solar energetic protons and a fast average transit speed of approximately 1500 km s⁻¹ of the interplanetary disturbance. A geomagnetic Kp index of more than 9 was observed after an interval of approximately eleven years since 1989. We found that return periods of extreme space weather (e.g., large flares, solar energetic proton events, and large geomagnetic storms) satisfied the Weibull distribution.  相似文献   

AMS 14C ages and petrological features for solidified fractures with carbonates at coastal outcrops of Yakushima Island, Japan     

Tomoaki Matsushita  Masahiko Osada  Manabu Takahashi 《Environmental Earth Sciences》2013,68(2):577-584

This paper describes the petrological features and the ages of rock fractures filled mainly with carbonates at coastal outcrops of Yakushima Island, Japan. Microscopic observation and geochemical analysis were used to investigate the petrological features and the compositions of the fracture fillings. In addition, AMS ¹⁴C dating was also performed to estimate the ages of them. Microscopic study indicated that the fracture fillings contain not only cementing materials but also lithic fragments from host rock and bioclasts. SEM observation showed that the cements exhibit the characteristic textures of beachrocks. The cements were identified as Mg-calcite from XRD analysis. It was also observed from geochemical analysis that there were at least two stages of precipitation within the fractures. In addition, AMS ¹⁴C dating for seventeen samples of fracture fillings showed that the ages range from 2,460 to 5,130 years BP which is found to be younger than that of the uplifted coral at Yakushima Island (approximately 5,300–5,600 years BP). The results suggest that the fractures were solidified after the coral was uplifted.  相似文献   

Erratum to: Temperature scaling pattern dependence on representative concentration pathway emission scenarios     

Yasuhiro Ishizaki  Hideo Shiogama  Seita Emori  Tokuta Yokohata  Toru Nozawa  Tomoo Ogura  Manabu Abe  Masakazu Yoshimori  Kiyoshi Takahashi 《Climatic change》2014,125(2):277-277

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