Distribution patterns and environmental correlates of Thaumarchaeota abundance in six deep subalpine lakes     

Cristiana Callieri  Salvador Hernández-Avilés  Michaela M. Salcher  Diego Fontaneto  Roberto Bertoni 《Aquatic Sciences - Research Across Boundaries》2016,78(2):215-225

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Charnock’s Roughness Length Model and Non-dimensional Wind Profiles Over the Sea   总被引：1，自引：1，他引：0  

Alfredo Peña  Sven-Erik Gryning 《Boundary-Layer Meteorology》2008,128(2):191-203

An analysis tool for the study of wind speed profiles over the water has been developed. The profiles are analysed using a modified dimensionless wind speed and dimensionless height, assuming that the sea surface roughness can be predicted by Charnock’s roughness length model. In this form, the roughness dependency on wind speed is extracted and the variations on the wind profile are due solely to atmospheric stability. The use of the Charnock’s non-dimensional wind profile is illustrated using data collected from a meteorological mast installed in the Danish North Sea. The best fit with the observed mean non-dimensional wind profile under neutral atmospheric conditions is found using a value of 1.2 × 10⁻² for Charnock’s parameter. The stability correction on the neutral wind profile suggested by the Businger-Dyer relations was found to perform well over the sea.  相似文献   

Measurements and Modelling of the Wind Speed Profile in the Marine Atmospheric Boundary Layer   总被引：1，自引：1，他引：0  

Alfredo Peña  Sven-Erik Gryning  Charlotte B. Hasager 《Boundary-Layer Meteorology》2008,129(3):479-495

We present measurements from 2006 of the marine wind speed profile at a site located 18 km from the west coast of Denmark in the North Sea. Measurements from mast-mounted cup anemometers up to a height of 45 m are extended to 161 m using LiDAR observations. Atmospheric turbulent flux measurements performed in 2004 with a sonic anemometer are compared to a bulk Richardson number formulation of the atmospheric stability. This is used to classify the LiDAR/cup wind speed profiles into atmospheric stability classes. The observations are compared to a simplified model for the wind speed profile that accounts for the effect of the boundary-layer height. For unstable and neutral atmospheric conditions the boundary-layer height could be neglected, whereas for stable conditions it is comparable to the measuring heights and therefore essential to include. It is interesting to note that, although it is derived from a different physical approach, the simplified wind speed profile conforms to the traditional expressions of the surface layer when the effect of the boundary-layer height is neglected.  相似文献   

A support for the existence of paleolakes and paleorivers buried under Saharan sand by means of “gravitational signal” from EIGEN 6C4     

Jaroslav Klokočník  Jan Kostelecký  Václav Cílek  Aleš Bezděk  Ivan Pešek 《Arabian Journal of Geosciences》2017,10(9):199

The goal of this study is to demonstrate that and how the recent gravitational and topographic data support the findings made by geologists and others as for the existence of the paleolakes and paleoriver systems, now buried under the sands of Sahara. It is always important and useful to have such an independent analysis supporting certain results, and this paper is such a case. We make use of the gravity disturbances (or anomalies), the Marussi tensor of the second derivatives of the disturbing geopotential, the gravitational invariants and their certain ratio, the strike angle and the virtual deformations. The geopotential is represented by the global combined (from satellite and terrestrial data) high-resolution gravity field model EIGEN 6C4 (till degree and order 2160 in spherical harmonic expansion). The topography is derived from the ASTER GDEM and ETOPO 1 models (both are used). With all these data, we confirm the existence of huge paleolakes or paleoriver systems under the Saharan sands known or anticipated in an independent way by geologists for the lakes MegaChad, Fazzan and Chotts; for Tamanrasset river valley; and Kufrah Basin, presumptive previous flow of the Nile River. Moreover, we suggest a part of the Grand Egyptian Sand Sea as another “candidate” for a paleolake and hence for a follow-up survey.  相似文献   

The inclusion of surface synoptic data in very short range predictions of convective events     

Zbyněk Sokol  Daniela Řezáčová  Petr Pešice 《Studia Geophysica et Geodaetica》1996,40(2):178-186

Summary Predictor vectors, including upper air as well as surface data, were used for categorical forecasting convective events over a subregion of the Czech territory, and the effect of including surface variables in the predictor vector was examined. While upper air data were considered as Perfect Prognosis, the surface data were successively included according to the time of their origin. The forecasting technique was based on linear multiple regression with learning, and the accuracy of the forecast was measured by the Critical Success Index. The input data from the three May-September periods in 1989–91 were used, and the first year served as the learning set. The aerological data from TEMP 12 UTC, simulating Perfect Prognosis, were the source of the upper air predictors. The performance of all, upper air, surface and combined, predictors were evaluated and compared. It turned out that the improvement of prediction accuracy due to the inclusion of surface variables was not negligible. Significant improvements were made in the forecasts of thunderstorm occurrence between 18 and 24 UTC.  相似文献   

Strontium isotope ratios in volcanic rocks from the northwestern part of the Hellenic arc     

G.G. Pe 《Chemical Geology》1975,15(1):53-60

${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios have been determined in fifteen volcanic rocks from the northwestern part of the Hellenic arc. They range from 0.7041 to 0.7134. There is no apparent correlation of strontium isotope values with any major chemical component or with Rb/Sr ratios. The ${}^{87}\text{Sr}{}^{86}\text{Sr}$ ratios appear to increase in a general way with increasing depth to the Benioff zone. The strontium isotope ratios are higher than from most island arcs; this is believed to be due to contamination.  相似文献   

Reviews     

Richard A. Reyment  A. Hubaux  D. F. Merriam  Mario Peña Daza  M. A. Romanova 《Mathematical Geosciences》1974,6(4):401-409

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Petrology and geochemistry of volcanic rocks of Aegina,Greece     

G. G. Pe 《Bulletin of Volcanology》1973,37(4):491-514

The Plio-Pleistocene cale-alkalic lavas of Aegina are comparable geochemically with similar lavas from elsewhere in the South Aegean arc. At least four differentiation series, largely of basaltic andesite to rhyodacite type, have been recognized in Aegina. Petrographical and geochemical evidence shows that lavas and xenoliths have a common origin. The mineralogy of the rocks suggests an alternation of hydrous and dry conditions during their formation. The chemical composition of the basic rocks, and of basic cognate xenoliths in the lavas, suggest that the parent material of all the lavas was of basic composition. Fractionation of the early formed phases is believed to have been the main process for the formation of the more acidic differentiates.  相似文献   

Post-fire management effects on sediment (dis)connectivity in Mediterranean forest ecosystems: Channel and catchment response     

Javier González-Romero  Manuel López-Vicente  Elena Gómez-Sánchez  Esther Peña-Molina  Pablo Galletero  Pedro Plaza-Alvarez  Daniel Moya  Jorge De las Heras  Manuel Esteban Lucas-Borja 《地球表面变化过程与地形》2021,46(13):2710-2727

Forest fires and post-fire practices influence sediment connectivity (SC). In this study, we use the ‘aggregated index of connectivity’ (AIC) to assess SC in five Mediterranean catchments (198–1090 ha) affected by a wildfire in 2012 in south-eastern Spain. Two temporal scenarios were considered, immediately after the fire and before post-fire management, and 2 years after the fire including all practices (hillslope barriers, check-dams, afforestation, salvage logging and skid trails). One LiDAR (light detection and ranging)-derived digital elevation model (DEM, 2 m × 2 m resolution) was generated, per scenario. The five catchment outlets were established as the computation target (AIC_OUT), and structural and functional SC were calculated. Index outputs were normalized to make the results of the non-nested catchments comparable (AIC_N-OUT). The output analysis includes the SC distribution along the catchments and at local scale (929 sub-catchments, 677 in the burned area), the hillslope and channel measures' effect on SC, and a sedimentological analysis using observed area-specific sediment yield (SSY) at 10 new (built after post-fire practices) concrete check-dams located in the catchments (SSY = 1.94 Mg ha⁻¹ yr⁻¹; σ = 1.22). The catchments with more circular shapes and steeper slopes were those with higher AIC_N-OUT. The structural SC maps – removing the rainfall erosivity influence – allowed evaluating the actual role played by the post-fire practices that reduced SC ( $\overline{x}$= − 1.19%; σ = 0.41); while functional SC was linked to the actual change of SC ( $\overline{x}$= + 5.32%; σ = 0.62). Hillslope treatments resulted in significant changes on AIC_N-OUT at sub-catchment scale with certain disconnectivity. A good and positive correlation was found between the SSY and the changes of AIC_N-OUT. However, the coarse DEM resolution explained the lack of effect of the rock check-dams – located on the secondary channels – on AIC_N-OUT. AIC_N-OUT proved to be a useful tool for decision making in post-fire restoration, but an optimal input data is still necessary to refine calculations.  相似文献   

Assessment of exotic fish impacts on water quality and zooplankton in a degraded semi-arid floodplain wetland   总被引：1，自引：0，他引：1  

David G. Angeler  Miguel Álvarez-Cobelas  Salvador Sánchez-Carrillo  Maria A. Rodrigo 《Aquatic Sciences - Research Across Boundaries》2002,64(1):76-86

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