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1.
Active roles of both sea surface temperature (SST) and its frontal characteristics to the atmosphere in the mid-latitudes have been investigated around the western boundary current regions, and most studies have focused on winter season. The present study investigated the influence of the variation of the summertime Oyashio extension SST front (SSTF) in modulating low-level cloud properties (i.e., low-level cloud cover [LCC], cloud optical thickness [COT], and shortwave cloud radiative effect [SWCRE]) on inter-annual timescales, based on available satellite and Argo float datasets during 2003–2016. First, we examined the mechanism of summertime SSTF variability itself. The strength of the SSTF (SSSTF), defined as the maximum horizontal gradient of SST, has clear inter-annual variations. Frontogenesis equation analysis and regression analysis for subsurface temperature indicated that the inter-annual variations of the summertime SSSTF in the western North Pacific are closely related to the variations of not surface heat flux, but western boundary currents, particularly the Oyashio Extensions. The response of low-level cloud to intensified SSSTF is that negative SWCRE with positive COT anomaly in the northern flank of the SSTF can be induced by cold SST anomalies. The spatial scale of the low-level cloud response was larger than the SST frontal scale, and the spatial distribution of the response was mainly constrained by the pathways of Kuroshio and Oyashio Extensions. Multi-linear regression analysis revealed that the local SST anomaly played largest role in modulating the SWCRE and COT anomalies among the cloud controlling factors (e.g., estimated inversion strength, air-temperature advection) accounting for more than 50% of the variation. This study provides an observational evidence of the active role of local SST anomalies in summertime associated with the western boundary currents to the oceanic low-level cloud.
相似文献2.
Light scattering and size distribution of particles in the surface waters of the North Pacific Ocean 总被引：1，自引：0，他引：1
The volume scattering function and size distribution of suspended particles in the surface water were determined in the North Pacific. The relationship between the scattering coefficient estimated from observed volume scattering function and cross-section concentration of the particles greater than 2.4m in diameter was found to be linear in both northern and southern regions of central North Pacific. Difference in the constant of proportionality between two regions, however, was very great. Moreover the constant in the southern region was too large compared with the values obtained by the Mie theory. This is considered to be due to the fact that particles smaller than 2.4m which were not measureable by the Coulter Counter, were neglected in the calculation of cross-section concentration. If small particles are taken into consideration, total cross-section concentration and scattering coefficient in the two regions tend to follow a linear relation. From the correlation between the scattering coefficient computed from size distribution and the volume scattering function, the refractive index of particles was estimated to be 1.03–1.05. By the same procedure, the refractive index of particles in Tateyama Harbour where the water was very turbid, was estimated to be also 1.03–1.05. This is in contrast to the result for the refractive index of particles originating from the river which flows into the harbour. This index was found to be 1.10–1.20. 相似文献
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Kotaro Kohno Koichiro Nakanishi Tomoka Tosaki Kazuyuki Muraoka Rie Miura Hajime Ezawa Ryohei Kawabe 《Astrophysics and Space Science》2008,313(1-3):279-285
Dense molecular medium plays essential roles in galaxies. As demonstrated by the tight and linear correlation between HCN(1–0)
and FIR luminosities among star-forming galaxies, from very nearby to high-z ones, the observation of a dense molecular component
is indispensable to understand the star formation laws in galaxies. In order to obtain a general picture of the global distributions
of dense molecular medium in normal star-forming galaxies, we have conducted an extragalactic CO(3–2) imaging survey of nearby
spiral galaxies using the Atacama Submillimeter Telescope Experiment (ASTE). From the survey (ADIoS; ASTE Dense gas Imaging
of Star-forming galaxies), CO(3–2) images of M 83 and NGC 986 are presented. Emphasis is placed on the correlation between
the CO(3–2)/CO(1–0) ratio and the star formation efficiency in galaxies. In the central regions of some active galaxies, on
the other hand, we often find enhanced or overluminous HCN(1–0) emission. The HCN(1–0)/CO(1–0) and HCN(1–0)/HCO+(1–0) intensities are often enhanced up to ∼0.2–0.3 and ∼2–3, respectively. Such elevated ratios have never been observed
in the nuclear starburst regions. One possible explanation for these high HCN(1–0)/CO(1–0) and HCN(1–0)/HCO+(1–0) ratios is X-ray induced chemistry in X-ray dominated regions (XDRs), i.e., the overabundance of the HCN molecule in
the X-ray irradiated dense molecular tori. If this view is true, the known tight correlation between HCN(1–0) and the star-formation
rate breaks in the vicinity of active nuclei. Although the interpretation of these ratios is still an open question, these
ratios have a great potential for a new diagnostic tool for the energy sources of dusty galaxies in the ALMA era because these
molecular lines are free from dust extinction. 相似文献
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Ryohei Takahashi Hiroharu Matsueda Victor M. Okrugin Naotatsu Shikazono Shuji Ono Akira Imai Elena D. Andreeva Koichiro Watanabe 《Resource Geology》2013,63(2):210-223
In Kamchatka, Central Koryak, Central Kamchatka and East Kamchatka metallogenic belts are distributed from northwest to southeast. K–Ar age, sulfur isotopic composition of sulfide minerals, and bulk chemical compositions of ores were analyzed for 13 ore deposits including hydrothermal gold‐silver and base metal, in order to elucidate the geological time periods of ore formation, relationship to regional volcanic belts, type of mineralization, and origin of sulfur in sulfides. The dating yielded ore‐forming ages of 41 Ma for the Ametistovoe deposit in the Central Koryak, 17.1 Ma for the Zolotoe deposit and 6.9 Ma for the Aginskoe deposit in the Central Kamchatka, and 7.4 Ma for the Porozhistoe deposit and 5.1 Ma for the Vilyuchinskoe deposit in the East Kamchatka metallogenic belt. The data combined with previous data of ore‐forming ages indicate that the time periods of ore formation in these metallogenic belts become young towards the southeast. The averaged δ34SCDT of sulfides are ?2.8‰ for the Ametistovoe deposit in Central Koryak, ?1.8‰ to +2.0‰ (av. ?0.1‰) for the Zolotoe, Aginskoe, Baranievskoe and Ozernovskoe deposits in Central Kamchatka, and ?0.7 to +3.8‰ (av. +1.7‰) for Bolshe‐Bannoe, Kumroch, Vilyuchinskoe, Bystrinskoe, Asachinskoe, Rodnikovoe, and Mutnovskoe deposits in East Kamchatka. The negative δ34SCDT value from the Ametistovoe deposit in Central Koryak is ascribed to the contamination of 32S‐enriched sedimentary sulfur in the Ukelayat‐Lesnaya River trough of basement rock. Comparison of the sulfur isotope compositions of the mineral deposits shows similarity between the Central Koryak and Magadan metallogenic belts, and East Kamchatka and Kuril Islands belts. The Central Kamchatka belt is intermediate between these two groups in term of sulfur isotopic composition. 相似文献
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Elena D. Andreeva Hiroharu Matsueda Victor M. Okrugin Ryohei Takahashi Shuji Ono 《Resource Geology》2013,63(4):337-349
Mineralogic studies of major ore minerals and fluid inclusion analysis in gangue quartz were carried out for the for the two largest veins, the Aginskoe and Surprise, in the Late Miocene Aginskoe Au–Ag–Te deposit in central Kamchatka, Russia. The veins consist of quartz–adularia–calcite gangue, which are hosted by Late Miocene andesitic and basaltic rocks of the Alnei Formation. The major ore minerals in these veins are native gold, altaite, petzite, hessite, calaverite, sphalerite, and chalcopyrite. Minor and trace minerals are pyrite, galena, and acanthine. Primary gold occurs as free grains, inclusions in sulfides, and constituent in tellurides. Secondary gold is present in form of native mustard gold that usually occur in Fe‐hydroxides and accumulates on the decomposed primary Au‐bearing tellurides such as calaverite, krennerite, and sylvanite. K–Ar dating on vein adularia yielded age of mineralization 7.1–6.9 Ma. Mineralization of the deposit is divided into barren massive quartz (stage I), Au–Ag–Te mineralization occurring in quartz‐adularia‐clays banded ore (Stage II), intensive brecciation (Stage III), post‐ore coarse amethyst (Stage IV), carbonate (Stage V), and supergene stages (Stage VI). In the supergene stage various secondary minerals, including rare bilibinskite, bogdanovite, bessmertnovite metallic alloys, secondary gold, and various oxides, formed under intensely oxidized conditions. Despite heavy oxidation of the ores in the deposit, Te and S fugacities are estimated as Stage II tellurides precipitated at the log f Te2 values ?9 and at log fS2 ?13 based on the chemical compositions of hypogene tellurides and sphalerite. Homogenization temperature of fluid inclusions in quartz broadly ranges from 200 to 300°C. Ore texture, fluid inclusions, gangue, and vein mineral assemblages indicate that the Aginskoe deposit is a low‐sulfidation (quartz–adularia–sericite) vein system. 相似文献
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Ryohei Suzuki Jun-Ichiro Ishibashi Miwako Nakaseama Uta Konno Urumu Tsunogai Kaul Gena Hitoshi Chiba 《Resource Geology》2008,58(3):267-288
The Yonaguni Knoll IV hydrothermal vent field (24°51′N, 122°42′E) is located at water depths of 1370–1385 m near the western edge of the southern Okinawa Trough. During the YK03–05 and YK04–05 expeditions using the submersible Shinkai 6500, both hydrothermal precipitates (sulfide/sulfate/carbonate) and high temperature fluids (Tmax = 328°C) presently venting from chimney‐mound structures were extensively sampled. The collected venting fluids had a wide range of chemistry (Cl concentration 376–635 mmol kg?1), which is considered as evidence for sub‐seafloor phase separation. While the Cl‐enriched smoky black fluids were venting from two adjacent chimney‐mound structures in the hydrothermal center, the clear transparent fluids sometimes containing CO2 droplet were found in the peripheral area of the field. This distribution pattern could be explained by migration of the vapor‐rich hydrothermal fluid within a porous sediment layer after the sub‐seafloor phase separation. The collected hydrothermal precipitates demonstrated a diverse range of mineralization, which can be classified into five groups: (i) anhydrite‐rich chimneys, immature precipitates including sulfide disseminations in anhydrite; (ii) massive Zn‐Pb‐Cu sulfides, consisting of sphalerite, wurtzite, galena, chalcopyrite, pyrite, and marcasite; (iii) Ba‐As chimneys, composed of barite with sulfide disseminations, sometimes associated with realgar and orpiment overgrowth; (iv) Mn‐rich chimneys, consisting of carbonates (calcite and magnesite) and sulfides (sphalerite, galena, chalcopyrite, alabandite, and minor amount of tennantite and enargite); and (v) pavement, silicified sediment including abundant native sulfur or barite. Sulfide/sulfate mineralization (groups i–iii) was found in the chimney–mound structure associated with vapor‐loss (Cl‐enriched) fluid venting. In contrast, the sulfide/carbonate mineralization (group iv) was specifically found in the chimneys where vapor‐rich (Cl‐depleted) fluid venting is expected, and the pavement (group v) was associated with diffusive venting from the seafloor sediment. This correspondence strongly suggests that the subseafloor phase separation plays an important role in the diverse range of mineralization in the Yonaguni IV field. The observed sulfide mineral assemblage was consistent with the sulfur fugacity calculated from the FeS content in sphalerite/wurtzite and the fluid temperature for each site, which suggests that the shift of the sulfur fugacity due to participation of volatile species during phase separation is an important factor to induce diverse mineralization. In contrast, carbonate mineralization is attributed to the significant mixing of vapor‐rich hydrothermal fluid and seawater. A submarine hydrothermal system within a back‐arc basin in the continental margin may be considered as developed in a geologic setting favorable to a diverse range of mineralization, where relatively shallow water depth induces sub‐seafloor phase separation of hydrothermal fluid, and sediment accumulation could enhance migration of the vapor‐rich hydrothermal fluid. 相似文献
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Abstract. The Mutnovskoe deposit located in the Porozhisto‐Asachinskaya metallogenic province of South Kamchatka, Russia, is a polymetallic vein and Au‐Ag quartz vein associated type of hydrothermal deposit. The Mutnovskoe deposit is located inside a paleo‐caldera structure at the center of the Mutnovsko‐Asachinskaya geothermal field of Pliocene ‐ Quaternary age, where active gold deposition is identified in hot spring precipitate. The Mutnovskoe deposit is subdivided into the north flank, the central flank and the south flank based on the vein distributions and mineral parageneses. The mineralized vein system is oriented N‐S hosted in diorite ‐ gabbroic diorite stock, volcanic rocks and sedimentary rocks of Miocene ‐ Pleistocene age. The mineralization stage I (polymetallic vein) mainly in the central and the south flanks is Zn‐Pb‐Cu‐Au‐Ag contained in sphalerite, galena and tetrahedrite‐tennantite group mineral. The stage II (Au‐Ag quartz vein) occurs in the north and the central flanks. The stage III (Mn‐sulfide and Mn‐Ca‐carbonate vein) occurs in the whole deposit area. Stage II is the typical Au‐Ag quartz‐adularia vein of low‐sulfidation type. Stage III is alabandite‐rhodochrosite‐quartz‐calcite vein. The K‐Ar ages are 1.3±0.1 Ma for stage I sericite in alteration zone, and 0.7±0.1 Ma for the stage II adularia in mineralized vein. Based on the fluid inclusion study, range of ore forming temperature of the Mutnovskoe deposit is 200 to 260d?C (av. 230d?C). Salinities of fluid inclusions indicate 2.2 to 5.7 wt% NaCl in sphalerite and 0.8 to 3.3 wt% NaCl in quartz for the stage I. Mineral paragenesis of the polymetallic vein (stage I) is characterized by a district zoning of tennantite and Cd‐rich sphalerite in the south flank and tetrahedrite and Mn‐rich sphalerite in the central flank, which is due to the fractional crystallizations of ore‐forming fluid. Depositional condition of the low sulfidation state is inferred for the Mutnovskoe deposit, where the polymetallic vein of the south flank is in relatively higher sulfidation state than the central flank. 相似文献
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Abstract. The Rodnikovoe gold deposit situated in a presently active hydrothermal system located north of the Mutnovsko-Asachinskaya geothermal area in southern Kamchatka, Far Eastern Russia, consists of typical low-sulfidation quartz-adularia veins in a host rock of diorite. The age of the mineralization was dated by the K-Ar method as 0.9 to 1.1 Ma based on adular-ia collected from the veins. Representative ore minerals in the deposit are electrum, argentite, aguilarite, polybasite, pearceite and lenaite. Dominant alteration minerals are adularia, α-cristobalite, chlorite, illite and kaolinite. Hydrothermal solutions of neutral pH were responsible for the mineralization, which is divided into six stages defined by tectonic boundaries. Gold mineralization occurred in stages I and III. Hydrothermal brecciation occurred during stages III, IV and VI. Stages II, IV, V and VI were barren. The estimated ore formation temperature based on a fluid inclusion study is 150 to 250 °C at a depth of approximately 170 m below the paleo-water table. Boiling of hydrothermal fluids is hypothesized as the cause of the intermittent deposition of gold ore. The sulfur and oxygen fugacities during the deposition of anhydrite prior to the hydrothermal brecciation were higher than those during the gold mineralization stages. The occurrence in the hydrothermal breccia of fragments of high grade Au-Ag and polymetallic ores suggests that higher grade mineralization of these metal ores might have occurred in a deeper portion of the deposit. 相似文献