Vortex structures around a hemispheric hump

The vortex structure formed in front of and behind a hemispheric surface hump has been studied in a water recirculating flume. In the recirculation zone behind the hemisphere, arched vortex tubes were formed. Up to a certain critical Reynolds number, each tube was shed individually from the recirculation zone. However, when the Reynolds number exceeded a critical value, several of the tubes coalesced in the recirculation zone before shedding. In front of the hemisphere, some parabolic vortex tubes formed. Their number increased with Reynolds number below its critical value and decreased above this value. The dimensionless height of the parabolic vortex tube decreased with Reynolds number.     

Specific accumulation and temporal trends of organochlorine contaminants in Dall's porpoises (Phocoenoides dalli) from Japanese coastal waters

Organochlorine compounds (OCs) such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlordane related compounds, hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB), tris(4-chlorophenyl) methane (TCPMe) and tris(4-chlorophenyl) methanol were determined in the blubber of Dall's porpoises (Phocoenoides dalli) collected from Japanese coastal waters in 1998/1999. Among OCs analyzed, PCBs were the predominant contaminants with concentrations ranging from 1.5 to 39 microg/g on a wet weight basis. OCs concentrations were relatively low and less variable in mature females possibly due to the lactational excretion from their bodies, while in males the concentrations were increased with body length. Concentrations and compositions of DDTs and HCHs showed significant differences between the truei-type population off the Pacific coast of northern Japan and dalli-type from the Sea of Japan/Okhotsk, suggesting its usefulness to discriminate different populations. OCs levels detected in truei-type porpoises collected in 1998/1999 were lower than those collected in 1984, except TCPMe. On the other hand, except DDTs, the residue levels of other organochlorines in dalli-type porpoises showed no significant decrease since 1984.     

Placental transfer of arsenic to fetus of Dall's porpoises (Phocoenoides dalli)

Concentrations of total arsenic and individual arsenic compounds were determined in liver, muscle, kidney and blubber of mother and fetus of Dall’s porpoises collected from off Sanriku, Japan, in the year 2000 to characterize the placental transfer of arsenic to fetus in cetaceans. Arsenic was detected in all the tissues of Dall’s porpoises. Total arsenic concentrations in liver, kidney, muscle and blubber were 0.76, 0.69, 0.35 and 0.55 μg/g wet wt, respectively, for mother and 0.28, 0.23, 0.26 and 0.07 μg/g wet wt, respectively, for fetus. In all the tissues, concentrations of total arsenic in mother Dall’s porpoise were higher than in fetus. Arsenic speciation revealed that arsenobetaine was the major arsenic compound in liver, kidney and muscle of both mother and fetus. The percentage of arsenobetaine to total arsenic ranged from 76.0 to 91.0% in the tissues. Dimethylarsinic acid, arsenocholine, methylarsonic acid and an unidentified arsenic compound were also detected in tissues of both mother and fetus as minor constituents, whereas tetramethylarsonium ion was not detected in tissues of the fetus. These results suggest that arsenobetaine, dimethylarsinic acid, arsenocholine and methylarsonic acid are transferable from mother to fetus in Dall’s porpoises. To our knowledge, this is the first report on placental transfer of arsenic compounds to fetus in marine mammals.     

Pre-Japan-ARGO: Experimental Observation of Upper and Middle Layers South of the Kuroshio Extension Region Using Profiling Floats

We deployed two profiling floats in the region south of the Kuroshio Extension in March 2000. Temperature and salinity profiles from a depth of 1500 × 10⁴ Pa to the surface are reported every two and four weeks, respectively. The floats performed very well for first four months after deployment. Later they failed in surfacing for a few months when the sea surface temperature in the region was high. The salinity sensors seemed to suffer from some damage during their failure-in-surfacing period. Despite this trouble, the results clearly demonstrate that the profiling float is a very useful and cost-effective tool for physical oceanographic observation in the open sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

Soil pore characteristics of evergreen and deciduous forests of the tropical monsoon region in Cambodia

Both evergreen and deciduous forests (Efs and Dfs) are widely distributed under similar climatic conditions in tropical monsoon regions. To clarify the hydraulic properties of the soil matrix in different forest types and their effects on soil water storage capacity, the soil pore characteristics (SPC) were investigated in Ef and Df stands in three provinces in Cambodia. Soils in the Ef group were characterized in common by large amounts of coarse pores with moderate pore size distribution and the absence of an extremely low K_s at shallow depths, compared to Df group soils. The mean available water capacity of the soil matrix (AWC_sm) for all horizons of the Ef and Df group soils was 0·107 and 0·146 m³ m^?3, respectively. The mean coarse pore volume of the soil matrix (CPV_sm) in the Ef and Df groups was 0·231 and 0·115 m³ m^?3, respectively. A water flow simulation using a lognormal distribution model for rain events in the early dry season indicated that variation in SPC resulted in a larger increase in available soil water in Ef soils than in Df soils. Further study on deeper soil layers in Ef and each soil type in Df is necessary for the deeper understanding of the environmental conditions and the hydrological modelling of each forest ecosystem. Copyright © 2010 John Wiley & Sons, Ltd.     

Decreasing precipitation extremes at higher temperatures in tropical regions

It has been often accepted that rising troposphere temperatures will lead to higher precipitation intensities. This argument is based on the Clausius?CClapeyron (C?CC) relation, which indicates an increase in atmospheric moisture storage capacity of approximately 7?% K^?1. However, recent studies carried out in mid-latitude regions indicate that changes in precipitation intensity as a function of temperature do not necessarily follow the C?CC relation. This study aimed to evaluate the correlation between precipitation extremes and temperature in tropical regions, using measured data obtained at low latitude ranges over Brazil. The results indicate that, at daily timescale, the C?CC relation alone is unlikely to explain the relation between precipitation extremes and temperatures in tropical regions. Additional aspects, such as moisture availability and the duration of precipitation events, should be further analyzed to allow a comprehensive understanding of the relationship between temperature and precipitation intensity. Moreover, we show that in tropical regions, higher temperatures may reduce the magnitude of extreme precipitation events at daily timescales, independent of the season of the year.     

乌鲁木齐天文站在月球探测同波束干涉测量中的作用

首先简要介绍同波束干涉测量技术,随后叙述中国科学院国家天文台乌鲁木齐天文站在2008年成功完成了约200 h日本月球卫星SELENE同波束较差甚长基线干涉测量,并阐述乌站在此次VLBI中的作用。给出利用SELENE的观测数据,分析、解算出乌站25 m天线与日本VERA网相关台站基线Rstar、Vstar的S1、S2、S3、X频段的较差相关相位、较差相关相位残差,以及对各频段的较差相关相位、较差相关相位残差比对,最后获得较差相位时延。结果显示,同波束甚长基线干涉测量比传统VLBI观测得到的群时延精度提高了1～2个量级。     

川滇菱形地块白垩纪古地磁学特征

在位于川滇菱形地块的西昌西南大德里向斜两翼的白恶系红和岩内采集古地磁学定向样品９６个,进行了古地学研究,研究结果表明,西昌晚白垩世末期的古地磁偏角为５．９°,古地磁倾角为４５．８°,地磁极位置为北纬８４．７°,东径１９３．３°,将该数据与作前期研究结果对比,则可见自楚雄至无谋,进而至西昌,其古地磁偏角逐渐靠近正北,而古地磁极纬度渐次升高,这反映了川滇菱形地块内的断块呈自西南至东北逐渐减弱的顺时针