Correlation of atmospheric occurences over the United States with some physical and chemical parameters. Part III: Frequencies of precipitation     

Alberto C. Montefinale  Liliana A. Masironi  Henry M. Papée 《Pure and Applied Geophysics》1963,54(1):207-211

Summary Correlation between some physical and chemical variables, measured at 28 stations of the United States Weather Bureau Network, and seasonal and annual frequencies of precipitation, has been attempted with the aim of gaining insight into the bearing of such variables, on occurrence of precipitation. — Concurrent trends of frequencies with local temperature functions, altitude parameters, precipitable water vapour increments, and some chemical species have been found.Contribution of the «Centro Nucleazione Aerosoli» of the National Research Council of Italy, Via Vettore 4 (Monte Sacro),Roma.  相似文献   

La pénétration de l'air froid dans une vallée alpine     

Max Bouët Dr. ès sc. 《Meteorology and Atmospheric Physics》1965,15(1):46-49

Résumé Les observations de deux stations situées à l'entrée de la vallée du Rhône et à l'intérieur de celle-ci permettent de déterminer dans une certaine mesure comment l'air froid pénètre dans cette longue vallée des Alpes suisses. L'accès se fait beaucoup plus souvent par-dessus les montagnes de l'Ouest ou du Nord que par le chenal de la vallée seulement.

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Summary The observations of two stations at the entrance and in the interior of the Rhône valley allow to a certain degree to determine how cold air penetrates this long extended valley of the Swiss Alps. The influx of air takes much more frequently place over the mountains in the West and North than through the trough of the valley.

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Zusammenfassung Die Beobachtungen von zwei Stationen, die am Eingang und im Inneren des Rhonetals gelegen sind, erlauben einigermaßen festzustellen, wie die Kaltluft in dieses langgestreckte Tal der Schweizeralpen eindringt. Dabei erfolgt der Luftzustrom viel häufiger über die Berge im W und N als ausschließlich durch die Talrinne.

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Avec 1 Figure  相似文献   

An attempt to the explanation and to the prediction of the eleven-year cycle of solar activity     

T. Németh 《Pure and Applied Geophysics》1966,63(1):205-210

Summary According to the author the reason of the subsistence of the 11 years' sunspot cycle is to be found in the conjunction of the planets. As a result of the investigations it has been stated that from among the nine planets the joint tidal effect of Venus-Jupiter-Earth is a decisive factor in the variations of sunspot activity. The above three planets are every 10.4 years and 12.0 years respectively, in a close conjunction. The mean value (11.2 years) is in an almost full accordance with the average cycle-period. The fluctuations of the period of the cycle come from the fact that the planets' getting into approximately one line takes a different time within each cycle. This time delay is the cause of the stronger or weaker sunspot activity, and of the shorter or longer cycles.  相似文献   

Diurnal changes in the bio-optical properties of the phytoplankton in the Alborán Sea (Mediterranean Sea)     

Jesús M. Mercado  Teodoro Ramírez  Dolores Corts  Marta Sebastin  Andreas Reul  Begoa Bautista 《Estuarine, Coastal and Shelf Science》2006,69(3-4):459

The changes in the phytoplankton absorption properties during a diurnal cycle were investigated at one station located in the north-western area of the Alborán Sea. The experiment was performed in spring when the water column was strongly stratified. This hydrological situation permitted the establishment of a deep chlorophyll a (chl a) fluorescence maximum (DFM) which was located on average close to the lower limit of the mixed layer and the nutricline. The relative abundance of pico-phytoplankton (estimated as its contribution to the total chl a) was higher in the surface, however, micro-phytoplankton dominated the community at the DFM level. Chl a specific absorption coefficient (a*(λ)) also varied with optical depth, with a* (the spectrally average specific absorption coefficient) decreasing by 30% at the DFM depth with respect to the surface. A significant negative correlation between the contribution of the micro-phytoplankton to the total chl a and a* was obtained indicating that a* reduction was due to changes in the packaging effect. Below the euphotic layer, a* increased three-fold with respect to the DFM, which agrees with the expected accumulation of accessory pigments relative to chl a as an acclimation response to the low available irradiance. The most conspicuous change during the diurnal cycle was produced in the euphotic layer where the chl a concentration decreased significantly in the afternoon (from a mean concentration of 1.1 μg L⁻¹ to 0.7 μg L⁻¹) and increased at dusk when it averaged 1.4 μg L⁻¹. In addition, a* and the blue-to-red absorption band ratio increased in the afternoon. These results suggest that a*(λ) diurnal variability was due to increase in photo-protective and accessory pigments relative to chl a. The variation ranges of a*(λ) at 675 and 440 nm (the absorption peaks in the red and blue spectral bands, respectively) in the euphotic layer were 0.01–0.04 and 0.02–0.10 m² mg⁻¹ chl a, respectively. Approximately 30% out of this variability can be attributed to the diurnal cycle. This factor should therefore be taken into account in refining primary production models based on phytoplankton light absorption.  相似文献   

Spatial patterns and environmental risks of ringnet fishing along the Kenyan coast     

P Thoya  S Pérez-Jorge  GM Okemwa  H Mwamlavya  A Tuda  N Wambiji 《African Journal of Marine Science》2020,42(1):23-33

Ringnet fishing began in the early 20th century and is practised worldwide, mainly to target nearshore pelagic species. The method was introduced to Kenya’s coastal waters by migrant fishers from Tanzania. However, the impacts of this fishing gear remain poorly assessed. We assessed the spatial distribution of ringnet fishing effort and its possible effects on ecosystem components, such as coral reefs, marine megafauna and marine protected areas, on the south coast of Kenya. We tracked 89 ringnet fishing trips made from December 2015 to January 2016 and used spatial multicriteria analysis to determine hotspots of possible environmental risks. The results showed that habitat type and bathymetric profile influenced the spatial distribution of ringnet fishing effort. Mixed seagrass and coral habitats had the highest concentration of the effort. Most of the habitats in the study area were moderately exposed to the impacts of the ringnet fishery. The study identifies high-risk areas that require spatial measures to minimise possible environmental risks of the gear both to habitats and to endangered sea turtles.  相似文献   

First results from the North Iceland experiment     

C. Riedel  A. Tryggvason  B. Brandsdottír  T. Dahm  R. Stéfansson  M. Hensch  R. Böðvarsson  K. S. Vogfjord  S. Jakobsdottír  T. Eken  R. Herber  J. Holmjarn  M. Schnese  M. Thölen  B. Hofmann  B. Sigurdsson  S. Winter 《Marine Geophysical Researches》2006,27(4):267-281

Between June 2004 and September 2004 a temporary seismic network was installed on the northern insular shelf of Iceland and onshore in north Iceland. The seismic setup aimed at resolving the subsurface structure and, thus, the geodynamical transition from Icelandic crust to typical oceanic crust along Kolbeinsey Ridge. The experiment recorded about 1,000 earthquakes. The region encloses the Tjörnes Fracture Zone containing the Husavik–Flatey strike-slip fault and the extensional seismic Grimsey Lineament. Most of the seismicity occurs in swarms offshore. Preliminary results reveal typical mid-ocean crust north of Grimsey and a heterogeneous structure with major velocity anomalies along the seismic lineaments and north–south trending subsurface features. Complementary bathymetric mapping highlight numerous extrusion features along the Grimsey Lineament and Kolbeinsey Ridge. The seismic dataset promises to deliver new insights into the tectonic framework for earthquakes in an extensional transform zone along the global mid-ocean ridge system.  相似文献   

A seismic refraction study of cretaceous oceanic lithosphere in the Northwest Pacific Basin     

Michel Bée  L. Dale Bibee 《Marine Geophysical Researches》1989,11(4):239-261

A seismic refraction study on old (110 Myr) lithosphere in the northwest Pacific Basin has placed constraints on crustal and uppermantle seismic structure of old oceanic lithosphere, and lithospheric aging processes. No significant lateral variation in structure other than azimuthally anisotropic mantle velocities was found, allowing the application of powerful amplitude modeling techniques. The anisotropy observed is in an opposite sense to that expected, suggesting the tectonic setting of the area may be more complex than originally thought. Upper crustal velocities are generally larger than for younger crust, supporting current theories of decreased porosity with crustal aging. However, there is no evidence for significant thickening of the oceanic crust with age, nor is there any evidence of a lower crustal layer of high or low velocity relative to the velocity of the rest of Layer 3. The compressional and shear wave velocities rule out a large component of serpentinization of mantle materials. The only evidence for a basal crustal layer of olivine gabbro cumulates is a 1.5 km thick Moho transition zone. In the slow direction of anisotropy, upper mantle velocities increase from 8.0 km s^-1 to 8.35 km s^-1 in the upper 15 km below the Moho. This increase is inconsistent with an homogeneous upper mantle and suggests that compositinal or phase changes occur near the Moho.  相似文献   

Evolution of the Axial Geometry of the Southwest Indian Ocean Ridge between the Melville Fracture Zone and the Indian Ocean Triple Junction – Implications for Segmentation on Very Slow-Spreading Ridges     

Parson  Lindsay  Sauter  Daniel  Mendel  Véronique  Patriat  Philippe  Searle  Roger 《Marine Geophysical Researches》1997,19(6):535-552

Geophysical data from 900 km of the Southwest Indian Ridge are used todescribe the pattern of evolution of the plate boundary between 61° Eand 70° E over the past 20 million years. The SWIR is anobliquely-opening, ultra slow-spreading axis, and east of61° E comprises a series of ridge sections, each about 100–120 kmin length. The orientation of these sections varies fromsub-orthogonal to oblique to the approximately N–S spreadingdirection. In general, the suborthogonal sections are shallower, commonlysubdivided into an array of discrete axial segments, and carry recognisablecentral magnetic anomalies. The majority of the oblique sections are single,continuous rifts without continuous axial magnetic signatures.Morphotectonics of the Southwest Indian Ridge crust have not previously beenwell constrained off-axis, and we here present sidescan sonar andswath bathymetric data up to 100 km from the ridge to demonstrate the complexities of its spatial and temporal evolution.A model is proposed that the segmentation style correlates with analong-axis variation between: (a) relatively thick crustal sections which overlie mantle sections with higher magmatic supply created in orthogonally-spreading segments and (b) those oblique sections associated with cooler, magmatically-starved mantle and thinner crust. These latter sections are formed at broad offset zones in theplate boundary, more precisely defined on faster-spreading ridges asnontransform discontinuities. The nonsystematic pattern of crustalconstruction, extensional basin formation and the absence of extension-parallel traces of discontinuities off-axis suggest that the oblique spreading sections are not fixed in space or time.  相似文献   

A map series of the Southern East Pacific Rise and its flanks, 15° S to 19° S     

Daniel S. Scheirer  Ken C. Macdonald  Donald W. Forsyth  Stephen P. Miller  Dawn J. Wright  Marie-Hélène Cormier  Charles M. Weiland 《Marine Geophysical Researches》1996,18(1):1-12

Four large-scale bathymetric maps of the Southern East Pacific Rise and its flanks between 15° S and 19° S display many of the unique features of this superfast spreading environment including abundant seamounts (the Rano Rahi Field), axial discontinuities, discontinuity migration, and abyssal hill variation. Along with a summary of the regional geology, these maps will provide a valuable reference for other sea-going programs on-and off-axis in this area, including the Mantle ELectromagnetic and Tomography (MELT) experiment.  相似文献   

Prolonged Magmatic and Tectonic Development of the Caribbean Igneous Province Revealed by a Diving Submersible Survey     

Mauffret  Alain  Leroy  Sylvie  Vila  Jean-Marie  Hallot  Erwan  Mercier de Lépinay  Bernard  Duncan  Robert A. 《Marine Geophysical Researches》2001,22(1):17-45

Using the diving submersible survey NAUTICA we investigated the central part of the Caribbean large igneous province (CLIP) to observe and sample internal portions of this proposed oceanic plateau. Most of the samples are gabbroic and doleritic rocks; basalts are scarce. Radiometric dating by ⁴⁰Ar/³⁹Ar incremental heating experiments indicate that the intrusive rocks are Campanian in age (81–75 Ma). In some places these intrusive rocks underlie older Santonian (85–83 Ma) extrusive basaltic rocks, suggesting that the Campanian rocks represent a sill injection and an underplating episode. Results of the diving program supplemented by information from ODP and DSDP drilling sites document a 20 m.y. period (94–75 Ma) of igneous activity in the submerged portion of the Caribbean large igneous province (CLIP). In the northern part of the Beata Ridge late Campanian and/or post Campanian uplift is documented by prominent Maastrichtian (71–65 Ma) erosion and the establishment of a Paleocene-middle Eocene (65–49 Ma) carbonate platform. During and after the uplift an extensional period is indicated by seismic images and the subsidence (3 km depth) of the carbonate platform. Paleocene ages (55–56 Ma) determined on some volcanic samples are attributed to localised decompression mantle melting that accompanied the extension. We document a prolonged period of magmatic and tectonic events that do not fit with the current models of short-lived plateau formation during mantle plume initiation but shares many similarities with the constructional histories of other oceanic large igneous provinces.  相似文献