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181.
182.
183.
In this study, a group of indices were defined regarding intensity (P),
area (S) and central position (λc, Φc) of
the Aleutian low (AL) in the Northern Hemisphere in winter, using seasonal
and monthly mean height field at 1000-hPa. These indices were calculated
over 60 winter seasons from 1948/1949 to 2007/2008 using reanalysis data.
Climatic and anomalous characteristics of the AL were analyzed based on
these indices and relationships between the AL, and general circulations
were explored using correlations between indices P, λc,
and Pacific SST, as well as Northern Hemisphere temperature and
precipitation. The main results are these: (1) AL is the strongest in
January, when the center shifts to the south and west of its climatological
position, and it is the weakest in December when the center shifts to the
north and east. (2) AL intensity (P) is negatively correlated with its
longitude (λc): a deeper low occurs toward the east and a
shallower low occurs toward the west. On a decadal scale, the AL has been
persistently strong and has shifted eastward since the 1970s, but reversal
signs have been observed in recent years. (3) The AL is stronger and is
located toward the east during strong El Nino winters and vice versa
during strong La Nina years; this tendency is particularly evident after
1975. The AL is also strongly correlated with SST in the North Pacific. It
intensifies and moves eastward with negative SST anomalies, and it weakens
and moves westward with positive SST anomalies. (4) Maps of significance
correlation between AL intensity and Northern Hemisphere temperature and
rainfall resemble the PNA teleconnection pattern in mid-latitudes in the
North Pacific and across North America. The AL and the Mongolian High are
two permanent atmospheric pressure systems adjacent to each other during
boreal winter over the middle and high latitudes in the Northern Hemisphere,
but their relationships with the El Nino/La Nina events and with
temperature and precipitation in the Northern Hemisphere are significantly
different. 相似文献
184.
Triaxial ellipsoid dimensions and rotational poles of seven asteroids from Lick Observatory adaptive optics images, and of Ceres 总被引:1,自引:0,他引:1
Seven main belt asteroids, 2 Pallas, 3 Juno, 4 Vesta, 16 Psyche, 87 Sylvia, 324 Bamberga, and 707 Interamnia, were imaged with the adaptive optics system on the 3 m Shane telescope at Lick Observatory in the near infrared, and their triaxial ellipsoid dimensions and rotational poles have been determined with parametric blind deconvolution. In addition, the dimensions and pole for 1 Ceres are derived from resolved images at multiple epochs, even though it is an oblate spheroid. 相似文献
185.
Organic materials dissolved in surface waters have long been implicated in metal binding and transport. In particular, fulvic and humic acids are considered to have a significant impact on speciation, total metal levels in solution and on the persistence of those metals. This work emphasizes the role played by dissolved organic matter (DOM) on the complexation of nickel, copper and cobalt and on its application to interpretation of surface water hydrogeochemical survey data. Waters from a number of well-known mining districts in Canada have been studied; in particular from Cobalt (Ontario), Sackville (New Brunswick) and Thetford Mines (Quebec). The diafiltration binding technique was used and shows that nickel, copper and cobalt are complexed significantly by DOM in natural waters. The tendency towards complexation was found to be Cu > Ni > Co. The binding functions determined were observed to be highly sensitive to pH and ligand:metal ratios; a gradation of binding site strength is evident.Data from some hydrogeochemical surveys conducted in the Kenora, Algoma and Ottawa districts of Ontario have been reinterpreted in the light of available data on the complexation behaviour of nickel, copper and cobalt. Occurrence of large water-borne anomalies unsupported by lake sediment loadings is most likely for cobalt and nickel and least likely for copper according to both field observations and experimental data. These studies provide good evidence for the formation of strong solution stable metal-organic species; the principal differences in persistence and migration behaviour are probably due to rates of coagulation and adsorption-precipitation processes which preferentially remove copper from solution. It is fair to conclude that these metals can be of use in mineral exploxation surveys using surface waters provided caution is exercised in interpretation of anomalies, especially in the absence of supporting sediment anomalies. Dissolved organic matter concentrations should always be determined when nickel, copper and cobalt are to be employed. 相似文献
186.
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188.
Derivation of design soil coefficients (S) and response spectral shapes for Eurocode 8 using the European Strong-Motion Database 总被引:1,自引:0,他引:1
A revision is presently under way to upgrade the status of the `Designrecommendations for earthquake resistance of structures', commonlyreferred to as Eurocode 8 (or EC8). In order to improve the definition ofthe design elastic response spectra (ERS) as defined in the Eurocode 8 –Part 1 (Draft May 2001), the values of the soil amplification factors havebeen calculated for sites on sedimentary soils, both stiff (category B) andsoft (category C), with respect to rock sites (category A), such ascontemplated in EC8. The work was performed by a systematic study ofresponse spectra as a function of magnitude and site conditions, usingrecords from the European Strong-Motion Database.The results confirm the occurrence of systematic spectral amplification onsedimentary soils with respect to reference rock in a large set of Europeanstrong motion data. Such amplification has been quantified through ameasure derived from the Housner Spectrum Intensity definition.The values of the soil coefficients recommended in the current version ofEC 8 are shown to be realistic for category C, in the case of a moderateseismicity context. However the values for subsoil class B need to besignificantly increased both for the moderate and high seismicity context. 相似文献
189.
190.
Yukihiro Matsuhisa Julian R. Goldsmith Robert N. Clayton 《Geochimica et cosmochimica acta》1979,43(7):1131-1140
Oxygen isotopic fractionations have been determined between quartz and water, albite and water, and anorthite and water at temperatures from 300 to 825°C, and pressures from 1.5. to 25 kbar. The equilibrium quartz-feldspar fractionation curves can be approximated by the following equations: 1000ln αQ?PI = (0.46 + 0.55β)106T?2 + (0.02 + 0.85β) between 500 and 800°C 1000ln αQ?PI = (0.79 + 0.90β)106T?2 — (0.43 ? 0.30β) between 400 and 500°C where β is the mole-fraction of anorthite in plagioclase.Application of these isotopic thermometer calibrations to literature data on quartz and feldspar gives temperatures for some metamorphic rocks which are concordant with quartz-magnetite temperatures. Plutonic igneous rocks typically have quartz-feldspar fractionations which are substantially larger than the equilibrium values at solidus temperatures, indicating substantial retrograde exchange effects. 相似文献