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71.
Bernard Fontaine Javier Garcia-Serrano Pascal Roucou Belen Rodriguez-Fonseca Teresa Losada Fabrice Chauvin Sébastien Gervois Sivarajan Sijikumar Paolo Ruti Serge Janicot 《Climate Dynamics》2010,35(1):95-114
Using both empirical and numerical ensemble approaches this study focuses on the Mediterranean/West African relationship in
northern summer. Statistical analyses utilize skin temperature, sea surface temperature, in situ and satellite rainfall, outgoing
longwave radiation (OLR) observations and reanalyzed data winds and specific humidity on isobaric surfaces. Numerical investigations
are based on a large set of sensitivity experiments performed on four atmospheric general circulation models (AGCM): ARPEGE-Climat3,
ECHAM4, LMDZ4 and UCLA7.3. Model outputs are compared to observations, discussed model by model and with an ensemble (multi-model)
approach. As in previous studies the anomalous Mediterranean warm events are associated with specific impacts over the African
monsoon region, i.e., a more intense monsoon, enhanced flux convergence and ascendances around the ITCZ, a strengthening of
low level moisture advection and a more northward location of ascending motion in West Africa. The results show also new features
(1) thermal variability observed in the two Mediterranean basins has unalike impacts, i.e. the western Mediterranean covaries
with convection in Gulf of Guinea, while the eastern Mediterranean can be interpreted as Sahelian thermal-forcing; (2) although
observations show symmetry between warming and cooling, modelling evidences only support the eastern warming influence; (3)
anomalous East warm situations are associated with a more northward migration of the monsoon system accompanied by enhanced
southwertely flow and weakened northeasterly climatological wind; (4) the multi-model response shows that anomalous East warm
surface temperatures generate an enhancement of the overturning circulation in low and high levels, an increase in TEJ (Tropical
Eeasterly Jet) and a decrease in AEJ (African Eeasterly Jet). 相似文献
72.
Javier Rodríguez Zaurín Joanna Holt Clive N. Tadhunter Rosa M. González Delgado 《Astrophysics and Space Science》2009,324(2-4):225-229
We use long-slit spectra taken with the William Herschel Telescope on La Palma and high-resolution Hubble Space Telescope imaging to study the gas kinematic in the halo of the ultraluminous infrared/radio galaxy PKS1345+12 (z=0.122). Our long-slit spectra show line splitting at the locations of massive star clusters ( $10^{6}<M_{\mathrm{SSC}}^{\mathrm{YSP}}<10^{7}$ M⊙), indicating that they are moving at up to 450 km?s?1 with respect to the local ambient gas. Given their kinematics, it is plausible that these super star clusters have been formed either in fast-moving gas streams or tidal tails that are falling back into the nuclear regions as part of the merger process, or as a consequence of jet-induced star formation linked to the extended, diffuse radio emission detected in the halo of the galaxy. 相似文献
73.
Jorge Del Río Vera Francisco Criado-Aldeanueva Jesús García-Lafuente F. Javier Soto-Navarro 《Global and Planetary Change》2009,68(3):232-235
Altimetry measurements over the Ionian region and tide gauge records along the southern Italian coasts have been combined to analyse the negative sea level trend over the Ionian basin in the last decades. The apparent decreasing trend should be better understood as an abrupt sea level drop in 1998 probably linked to changes in the surface circulation in the Ionian basin induced by the Eastern Mediterranean Transient, which changed from anticyclonic to cyclonic about March 1998. From then onwards, a rising rate of 7.9 ± 0.9 mm/year is observed over the basin. 相似文献
74.
Eduardo Luquin Miguel A. Campo-Bescós Rafael Muñoz-Carpena Ronald L. Bingner Richard M. Cruse Henrique G. Momm Robert R. Wells Javier Casalí 《地球表面变化过程与地形》2021,46(10):1909-1925
Ephemeral gully (EG) erosion has an important impact on agricultural soil losses and increases field surface hydrology connectivity and transport of pollutants to nearby water bodies. Watershed models including an EG component are scarce and not yet properly evaluated. The objective of this study is to evaluate the capacity of one such tool, AnnAGNPS, to simulate the evolution of two EG formed in a conservation tillage system. The dataset for model testing included runoff measurements and EG morphological characteristics during 3 years. Model evaluation focused on EG evolution of volume, width, and length model outputs, and included calibration and testing phases and a global sensitivity analysis (GSA). While the model did not fully reproduce width and length, the model efficiency to simulate EG volume was satisfactory for both calibration and testing phases, supporting the watershed management objectives of the model. GSA revealed that the most sensitive factors were EG depth, critical shear stress, headcut detachment exponent coefficient b, and headcut detachment leading coefficient a. For EG outputs the model was additive, showing low sensitivity to interactions between the inputs. Prediction of EG spatial evolution on conservation tillage systems requires improved development of gully erosion components, since many of the processes were developed originally for traditional tillage practices or larger channel systems. Our results identify the need for future research when EG form within conservation tillage systems, in particular to study gully headcut, soil erodibility, and width functions specific to these practices. 相似文献
75.
Deep‐water dunes on drowned isolated carbonate terraces (Mozambique Channel,south‐west Indian Ocean)
Elda Miramontes Stephan J. Jorry Gwenael Jouet John W. Counts Simon Courgeon Pascal Le Roy Charline Guerin F. Javier Hernndez‐Molina 《Sedimentology》2019,66(4):1222-1242
Subaqueous sand dunes are common bedforms on continental shelves dominated by tidal and geostrophic currents. However, much less is known about sand dunes in deep‐marine settings that are affected by strong bottom currents. In this study, dune fields were identified on drowned isolated carbonate platforms in the Mozambique Channel (south‐west Indian Ocean). The acquired data include multibeam bathymetry, multi‐channel high‐resolution seismic reflection data, sea floor imagery, a sediment sample and current measurements from a moored current meter and hull‐mounted acoustic Doppler current profiler. The dunes are located at water depths ranging from 200 to 600 m on the slope terraces of a modern atoll (Bassas da India Atoll) and within small depressions formed during tectonic deformation of drowned carbonate platforms (Sakalaves Seamount and Jaguar Bank). Dunes are composed of bioclastic medium size sand, and are large to very large, with wavelengths of 40 to 350 m and heights of 0·9 to 9·0 m. Dune migration seems to be unidirectional in each dune field, suggesting a continuous import and export of bioclastic sand, with little sand being recycled. Oceanic currents are very intense in the Mozambique Channel and may be able to erode submerged carbonates, generating carbonate sand at great depths. A mooring located at 463 m water depth on the Hall Bank (30 km west of the Jaguar Bank) showed vigorous bottom currents, with mean speeds of 14 cm sec?1 and maximum speeds of 57 cm sec?1, compatible with sand dune formation. The intensity of currents is highly variable and is related to tidal processes (high‐frequency variability) and to anticyclonic eddies near the seamounts (low‐frequency variability). This study contributes to a better understanding of the formation of dunes in deep‐marine settings and provides valuable information about carbonate preservation after drowning, and the impact of bottom currents on sediment distribution and sea floor morphology. 相似文献
76.
The aim of this study is to present an automatic approach for olive tree dendrometric parameter estimation from airborne laser scanning (ALS) data. The proposed method is based on a unique combination of the alpha-shape algorithm applied to normalized point cloud and principal component analysis. A key issue of the alpha-shape algorithm is to define the α parameter, as it directly affects the crown delineation results. We propose to adjust this parameter based on a group of representative trees in an orchard for which the classical field measurements were performed. The best value of the α parameter is one whose correlation coefficient of dendrometric parameters between field measurements and estimated values is the highest. We determined crown diameters as principal components of ALS points representing a delineated crown. The method was applied to a test area of an olive orchard in Spain. The tree dendrometric parameters estimated from ALS data were compared with field measurements to assess the quality of the developed approach. We found the method to be equally good or even superior to previously investigated semi-automatic methods. The average error is 19% for tree height, 53% for crown base height, and 13% and 9% for the length of the longer diameter and perpendicular diameter, respectively. 相似文献
77.
Pablo?SarricoleaEmail authorView authors OrcID profile Oliver?Meseguer-Ruiz Javier?Martín-Vide Luis?Outeiro 《Theoretical and Applied Climatology》2018,134(1-2):193-204
Atmospheric circulation patterns in southern Chile (42° 30′ S) were studied in order to determine and analyse the most characteristic synoptic types and their recent trends, as well as to gain an understanding of how they are associated with low-frequency variability patterns. According to the Jenkinson and Collison (J&C) classification method, a 16-point grid of sea-level pressure data was employed. The findings reveal that some synoptic types show statistically significant trends with a 95% confidence level, positively for anticyclonic westerly hybrids (AW) and advective types for third and fourth quadrant wind flows (W, NW, and N) and negatively for SW and cyclonic hybrids (CS and CSW). A model has been constructed of the linear regression of some weather types with teleconnections that most affect Chile: the undetermined types (U), AW were associated with El Niño or the warm phase of the Pacific Decadal Oscillation (PDO), whereas the cyclonic northerly and cyclonic northeasterly types (CN and CNE) were associated with La Niña or cool phase of the PDO. The weather types associated with Antarctic Oscillation (AAO) in its positive phase are anticyclonic northerly and northeasterly and northerly advection types, while in its negative phase are cyclonic southwesterly and advection types. 相似文献
78.
Acero Francisco Javier Fernández-Fernández María Isabel Carrasco Víctor Manuel Sánchez Parey Sylvie Hoang Thi Thu Huong Dacunha-Castelle Didier García José Agustín 《Theoretical and Applied Climatology》2018,133(1-2):605-617
Theoretical and Applied Climatology - Heat wave (HW) events are becoming more frequent, and they have important consequences because of the negative effects they can have not only on the human... 相似文献
79.
Javier Alcocer Elva G. Escobar Alfonso Lugo Luis A. Oseguera 《International Journal of Salt Lake Research》1999,8(2):113-126
The effects of multiple stressors on the benthic macroinvertebrate community were monitored in Tecuitlapa Norte, a shallow,
perennially-astatic, warm, mesosaline, sodaalkaline lake in Mexico. Physico-chemical and biological variables were determined
monthly for one year. Tecuitlapa Norte displayed a clear seasonal environmental pattern (dry and rainy seasons). The benthic
macroinvertebrate community consisted of five species:Culicoides occidentalis sonorensis Jorgensen,Ephydra hians Say,Stratiomys sp.,Eristalis sp., andLimnophora sp. of which the first two were dominant and the rest scarce.C. occidentalis was the most important species numerically (76 percent of the total), whileE. hians dominated the biomass (73 percent of the total). Primarily salinity and secondarily pH appear to be the most important environmental
factors controlling dominance of benthic organisms in Tecuitlapa Norte. Seasonal abundance dynamics of the dominant organisms
was associated with phases in their reproductive cycles: environmentally-triggered (i.e., temperature rise, water-level descent)
pupation and emergence periods. We concluded that whereas physical and chemical factors (i.e., salinity, pH) exerted the primary
control on benthic macroinvertebrate community composition in Tecuitlapa Norte, another assembly of variables (e.g., water-level,
temperature) influenced species distribution and abundance. 相似文献
80.
Javier F. Pacheco Carlos A. Mortera-Gutirrez Hugo Delgado Shri K. Singh Raúl W. Valenzuela Nicolai M. Shapiro Miguel A. Santoyo Alejandro Hurtado Ricardo Barrn Esteban Gutirrez-Moguel 《Journal of South American Earth Sciences》1999,12(6):55
We studied a sequence of small earthquakes that occurred during the months of April and May of 1997, in Jalisco, southwestern Mexico. The earthquakes were located along a set of active faults that form the Zacoalco half-graben (La Lima fault system), west of Lake Chapala, within the rift–rift–rift triple junction. A total of 33 events were located, with magnitudes ranging from 1.5 to 3.5, recorded by a portable array of broadband seismographs. We identified two groups of events: one corresponding to a shallow normal fault, synthetic to La Lima fault system, and another group associated with a deeper fault. The events that occurred on the synthetic fault show normal faulting oriented on a NW–SE plane, dipping shallowly towards the SW. The other group of mechanisms showed either a normal fault oriented NW–SE and dipping steeply to the NE, or a very shallow-dipping normal fault, dipping to the SW. Earthquake distribution and fault plane solutions suggest that the Zacoalco half-graben developed from blocks that rotate as slip occurs on listric faults. These mechanisms could represent the type of motion expected for larger earthquakes in the area, like the one that occurred in 1568. 相似文献