Analysis of dust events in 2008 and 2009 using the lidar network, surface observations and the CFORS model     

Nobuo Sugimoto  Yukari Hara  Atsushi Shimizu  Tomoaki Nishizawa  Ichiro Matsui  Masataka Nishikawa 《Asia-Pacific Journal of Atmospheric Sciences》2013,49(1):27-39

The Asian dust events in 2008 (May 24–June 4 in 2008) and in 2009 (March 12–25, October 13–26, and December 15–28 in 2009) were analyzed with the lidar network observations, surface observations in China, Korea, Japan, and Mongolia, and with the chemical transport model CFORS. Transport of Asian dust and mixing of dust with air pollution aerosols were studied. The event of May 24 to June 4 in 2008 was a significant event unusually late in the spring dust season. The dust event of March 12–25, 2009 was an interesting example of elevated dust layer, and transport of dust from the elevated dust layer to the ground by the boundary layer activity was observed with the lidars and surface observations in Japan. The concentration of air pollution aerosols was relatively high during the dust event, and the results suggest that vertical structure as well as transport path is important for the mixing of dust and air pollution aerosols. The dust events in October and December 2009 were examples of dust events in autumn and winter. The online mode CFORS reproduced the observation data generally well, except for the event of May 24 to June 4 in 2008. The results of the fourdimensional variational assimilation of the lidar network data reproduced the dust concentration in Korea and Japan reasonably in that event.  相似文献   

Regional extraction of flexural-toppled slopes in epicentral regions of subduction earthquakes along the Nankai Trough using DEMs     

Atsuko Nonomura  Shuichi Hasegawa 《Environmental Earth Sciences》2013,68(1):139-149

In the epicentral region of subduction earthquakes, large-scale landslides are triggered by strong shaking of slopes weakened by flexural toppling. The distribution of flexural-toppled slopes is the primary information for predicting and mitigating landslide damage beforehand. This study proposes and tests a simple algorithm for extracting flexural-toppled slopes on a regional basis from a 10-m resolution digital elevation model by windows of two sizes. Local relief is extracted with a large window (200 × 200 pixels), and microtopography is extracted with a small window (3 × 3 pixels). The algorithm was derived from the region of the Kanagi-kuzure landslide in Shikoku, and tested at Aka-kuzure landslide in Honshu in Japan. Both areas are underlain by strongly tilted sedimentary rocks in epicentral regions of subduction earthquakes along the Nankai Trough.  相似文献   

Spreading of warm water from the Kuroshio Extension into the Perturbed Area   总被引：1，自引：0，他引：1  

Susana Sainz-Trápaga  Takashige Sugimoto 《Journal of Oceanography》1998,54(3):257-271

The path of the Kuroshio Extension describes two stationary meanders with crests at approximately 144°E and 150°E. The short-term meridional fluctuations of the warm water spreading northward from the first crest at the surface and its vertical structure were analyzed by using 5-day-mean surface temperature maps published by JAFIC, montly 100-m-depth temperature maps edited by the JMA, and CTD data obtained by the R.Vs.Kofu-Maru, Hakuho-Maru andTansei-Maru cruises from 1990 to 1994. A Northern Boundary of the Spreak Kuroshio Water (NBSKW) and a Southern Boundary of the Spread Kuroshio Water (SBSKW) at the surface were defined as the northern and southern boundary of the pronounced meriodional temperature gradients, respectively. The vertical structure of the Spread Kuroshio Water was analyzed in terms of its T-S properties. The location of the NBSKW at the surface corresponds well with the northern boundary of the subsurface high salinity water that represents the Spread Kuroshio Water. The short-term meridional fluctuations of the northern and southern boundary of the Spread Kuroshio Water at the surface were studied through the spectral analysis of the maximum latitude of the two lines defined. We obtained the following results: (1) the meridional fluctuations of the NBSKW and SBSKW at the first creast have major periods between 16 and 38 days; (2) the 50 day running mean of the SBSKW at the first crest, for the purpòse of this study, can be generally used as indicative of the location of the Kuroshio axis; and (3) the northward extent of the Spread Kuroshio Water and the velocity of the meridional shift suggest seasonal variability that could be related with their vertical structure.  相似文献   

Temporal variations of the net Kuroshio transport and its relation to atmospheric variations   总被引：1，自引：0，他引：1  

Shusaku Sugimoto  Kimio Hanawa  Kumiko Narikiyo  Megumi Fujimori  Toshio Suga 《Journal of Oceanography》2010,66(5):611-619

Temporal variations of the net Kuroshio transport are investigated using long-term hydrographic data from repeat section of the 137°E meridian from the south of Japan (34°N) to New Guinea (1°S) conducted by the Japan Meteorological Agency. In this study, boundaries of the Kuroshio and the Kuroshio Counter Current (KCC) are defined based on the sea surface dynamic height distribution. Westward flows associated with the KCC and cold-core eddy north of the Kuroshio are removed from the eastward flow associated with the Kuroshio in order to estimate the net Kuroshio transport strictly. The net Kuroshio transport reveals low-frequency variations: significant signals on a decadal (about 10-year) timescale. The variations of net Kuroshio transport are predominantly caused by changes in the magnitude of oceanic current speed fields associated with a vertical movement of the main pycnocline depth around the southern boundary of the Kuroshio: deepening of the main pycnocline around the southern boundary of the Kuroshio forms a sharp northern upward-tilting slope of the isopycnal surfaces at the Kuroshio region, and eventually the net Kuroshio transport increases together with the Kuroshio eastward transport. By using a wind-driven hindcast model, it is found that the main pycnocline depth variation results from the first-mode baroclinic Rossby waves attributable to two types of Aleutian Low (AL) changes: a change in the magnitude of AL and meridional movement of AL.  相似文献   

Trends in pCO2 and sea–air CO2 flux over the global open oceans for the last two decades     

Yosuke Iida  Atsushi Kojima  Yusuke Takatani  Toshiya Nakano  Hiroyuki Sugimoto  Takashi Midorikawa  Masao Ishii 《Journal of Oceanography》2015,71(6):637-661

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Current observation system using ship drift and its applications in Kumano-nada and Enshu-nada Seas     

Takashige Sugimoto  Masato Kobayashi 《Journal of Oceanography》1987,43(6):363-376

A continuous observation system of ship drift of ferry boats was developed using Loran C, ship direction, ship speed and wind velocity measurement. A formula to estimate the wind-driven lateral drift of the boat is proposed, and a measuring system of the surface current is described, including a discussions on its usefullness to monitor day-to-day variations of the circulation patterns in the coastal boundary regions of the Kuroshio.This system was applied to observe variations of the circulation in the Kumano-nada, and Enshu-nada Seas south of Japan. Some preliminary results were obtained by using this system as well as other methods. This work focuses on the behavior of warm eddies in the Kumano-nada Sea. The surface current patterns that include these phenomena obtained by the use of the ship drift show good correspondence with currents and thermal structures observed with GEK, CTD, moored current meters and satellite thermal images.  相似文献   

Biological productivity of meso-scale eddies caused by frontal disturbances in the Kuroshio   总被引：1，自引：0，他引：1  

Kimura  Shingo; Kasai  Akihide; Nakata  Hideaki; Sugimoto  Takashige; Simpson  John H.; Cheok  Joseph V. S. 《ICES Journal of Marine Science》1997,54(2):179-192

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Short-Range Prediction Experiments with Operational Data Assimilation System for the Kuroshio South of Japan   总被引：3，自引：3，他引：3  

Masafumi Kamachi  Tsurane Kuragano  Satoshi Sugimoto  Kumi Yoshita  Toshiyuki Sakurai  Toshiya Nakano  Norihisa Usui  Francesco Uboldi 《Journal of Oceanography》2004,60(2):269-282

The short-range (one month) variability of the Kuroshio path was predicted in 84 experiments (90-day predictions) using a model in an operational data assimilation system based on data from 1993 to 1999. The predictions started from an initial condition or members of a set of initial conditions, obtained in a reanalysis experiment. The predictions represent the transition from straight to meander of the Kuroshio path, and the results have been analyzed according to previously proposed mechanisms of the transition with eddy propagation and interaction acting as a trigger of the meander and self-sustained oscillation. The reanalysis shows that the meander evolves due to eddy activity. Simulation (no assimilation) shows no meander state, even with the same atmospheric forcing as the prediction. It is suggested therefore that the initial condition contains information on the meander and the system can represent the evolution. Mean (standard deviation) values of the axis error for all 84 cases are 13, 17, and 20 (10, 10, and 12) km, in 138.5°E, in the 30-, 60-, and 90-day predictions respectively. The observed mean deviation from seasonal variation is 30 km. The predictive limit of the system is thus about 80 days. The time scale of the limit depends on which stage in the transition is adopted as the initial condition. The gradual decrease of the amplitude in a stage from meander to straight paths is also predicted. The predictive limit is about 20 days, which is shorter than the prediction of the opposite transition. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Behavior of Warm-Core Rings in a Double-Gyre Wind-Driven Ocean Circulation Model     

Sachihiko Itoh  Takashige Sugimoto 《Journal of Oceanography》2002,58(5):651-660

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Occurrence characteristics of chaetognath species along the PM transect in the Japan sea during 1972–2002     

Naoki Nagai  Kazuaki Tadokoro  Kazunori Kuroda  Takashige Sugimoto 《Journal of Oceanography》2006,62(5):597-606

A long-term variation in dominant species of chaetognaths in the Tsushima Warm Current was analyzed using samples collected four times a year from 1972 to 2002 by the Maizuru Marine Observatory along the PM transect in the Japan Sea. Of 19 occurring species, 13 subtropical species formed a major portion of the standing stock. Species richness in the study area was similar to that in the East China Sea and the South China Sea. Four species, Sagitta minima, S. nagae, S. enflata, S. elegans dominated in the upper 150 m water column. The most dominant species per season were S. minima in both winter and autumn, S. elegans in spring and S. nagae in summer. Water temperature and salinity ranges of the most frequent occurrence for three dominant species revealed a common tendency in the order of S. nagae > S. minima > S. enflata towards colder temperature and higher salinity. Inter-annual abundance of chaetognath species fluctuated proportionally in response to the warm or cool phases in water temperature. Water temperature was a fundamental factor in regulating distributional occurrence, being more decisive than salinity. Changes of both dominant species and species numbers in relation to the reduced abundance during winter to spring and the subsequent increase during summer to autumn might be caused by specific differences in optimum temperature. Chaetognath species are important as an indicator of water masses and significant for our understanding of changes and evaluations of the Japan Sea ecosystem.  相似文献