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51.
On December 20, 2004 the Minor Planet Center issued the Minor Planet Electronic Circular (MPEC) 2004-Y25 announcing the discovery of a new Near Earth Asteroid (NEA) with designation 2004 MN4. Only two days later, when the Christmas holidays were about to begin, it was already apparent that this asteroid, currently known as Apophis, would be notorious: our close-approach monitoring system, CLOMON2, was already showing a Virtual Impactor (VI) in 2029 reaching the level 2 in the Torino Scale, the first asteroid to reach that level since our monitoring system had been operational. However, this was just the beginning of what it was to come in the subsequent days. In this paper we will give an overview of the NEODyS-CLOMON2 system and provide the details on how Apophis’ collision scenario evolved, the way NEODyS’ team handled it and the crazy 2004’ Christmas holidays we had due to this unexpected guest. 相似文献
52.
The paper presents closed‐form solutions for stress and displacement influence functions for stress discontinuity (SD) and displacement discontinuity (DD) elements, for a two‐dimensional plane‐strain elastic, transversely anisotropic medium. The solutions for SD elements are based on Kelvin's problem and for DD elements on the concept of dipoles. Stress and displacement influence functions are derived for the following elements: constant SD, linear SD, constant DD, linear DD, square root DD, parabolic DD, constant DD surface, and linear DD surface elements. The formulations are incorporated into FROCK, a hybridized boundary element method code, and are validated by providing comparisons between the results from FROCK and the finite element code ABAQUS. A limited parametric analysis shows the effects of slight anisotropy on the stress field around the tip of a crack and of the orientation of the crack with respect to the axes of elastic symmetry. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
53.
Spatially distributed tracer‐aided modelling to explore water and isotope transport,storage and mixing in a pristine,humid tropical catchment 下载免费PDF全文
Joni Dehaspe Christian Birkel Doerthe Tetzlaff Ricardo Sánchez‐Murillo Ana María Durán‐Quesada Chris Soulsby 《水文研究》2018,32(21):3206-3224
Rapidly transforming headwater catchments in the humid tropics provide important resources for drinking water, irrigation, hydropower, and ecosystem connectivity. However, such resources for downstream use remain unstudied. To improve understanding of the behaviour and influence of pristine rainforests on water and tracer fluxes, we adapted the relatively parsimonious, spatially distributed tracer‐aided rainfall–runoff (STARR) model using event‐based stable isotope data for the 3.2‐km2 San Lorencito catchment in Costa Rica. STARR was used to simulate rainforest interception of water and stable isotopes, which showed a significant isotopic enrichment in throughfall compared with gross rainfall. Acceptable concurrent simulations of discharge (Kling–Gupta efficiency [KGE] ~0.8) and stable isotopes in stream water (KGE ~0.6) at high spatial (10 m) and temporal (hourly) resolution indicated a rapidly responding system. Around 90% of average annual streamflow (2,099 mm) was composed of quick, near‐surface runoff components, whereas only ~10% originated from groundwater in deeper layers. Simulated actual evapotranspiration (ET) from interception and soil storage were low (~420 mm/year) due to high relative humidity (average 96%) and cloud cover limiting radiation inputs. Modelling suggested a highly variable groundwater storage (~10 to 500 mm) in this steep, fractured volcanic catchment that sustains dry season baseflows. This groundwater is concentrated in riparian areas as an alluvial–colluvial aquifer connected to the stream. This was supported by rainfall–runoff isotope simulations, showing a “flashy” stream response to rainfall with only a moderate damping effect and a constant isotope signature from deeper groundwater (~400‐mm additional mixing volume) during baseflow. The work serves as a first attempt to apply a spatially distributed tracer‐aided model to a tropical rainforest environment exploring the hydrological functioning of a steep, fractured‐volcanic catchment. We also highlight limitations and propose a roadmap for future data collection and spatially distributed tracer‐aided model development in tropical headwater catchments. 相似文献
54.
Antonio Luis Montealegre-Gracia María Teresa Lamelas-Gracia Alberto García-Martín Juan de la Riva-Fernández Francisco Escribano-Bernal 《地理信息系统科学与遥感》2017,54(5):721-740
The aim of study is to map the carbon dioxide (CO2) emission of the aboveground tree biomass (AGB) in case of a fire event. The suitability of low point density, discrete, multiple-return, Airborne Laser Scanning (ALS) data and the influence of several characteristics of these data and the study area on the results obtained have been evaluated. A sample of 45 circular plots representative of Pinus halepensis Miller stands were used to fit and validate the model of AGB. The ALS point clouds were processed to obtain the independent variables and a multivariate linear regression analysis between field data and ALS-derived variables allowed estimation of AGB. Then, the influence of several characteristics on the residuals of the model was analyzed. Finally, conversion factors were applied to obtain the CO2 values. The AGB model presented a R2 value of 0.84 with a relative root-mean-square error of 27.35%. This model included ALS variables related to vegetation height variability and to canopy density. Terrain slope, aspect, canopy cover, scan angle and the number of laser returns did not influence AGB estimations at plot level. 相似文献
55.
David Serrano Giné Joan Jurado Rota María Yolanda Pérez Albert Carla Bonfill Cerveró 《The Professional geographer》2018,70(3):412-422
The aim of this article is to introduce the Beach Crowding Index (BCI), a procedure to assess the social carrying capacity of vulnerable beaches. The study uses the people at one time (PAOT) approach and data gathered weekly throughout the bathing season regarding the number of beachgoers in 100 m2 cells of the beach to assess how many beachgoers it can comfortably hold. The procedure is based on fieldwork, interviews with beachgoers, and geographic information system (GIS) analysis and has been tested on four beaches in protected areas on the Spanish Mediterranean coast. On a scale from 0 to 4, minimum scores throughout the bathing season are 0.7 and maximum 3.7, although results showed wide variation between the beaches, the section of the beach, and the time of day. This study suggests that determining the location of beachgoers and collecting a long-term series of data is fundamental to assessing social carrying capacity and that the BCI procedure can be used for a large number of applications. 相似文献
56.
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
57.
María?CazorlaEmail authorView authors OrcID profile 《Journal of Atmospheric Chemistry》2017,74(3):377-398
In this paper we present first-time measurements of ozone profiles from a high altitude station in Quito, Ecuador (0.19°S, 78.4°W, and 2391 masl) taken from June 2014 to September 2015. We interpret ozone observations in the troposphere, tropopause, and stratosphere through a zonal comparison with data from stations in the Atlantic and Pacific (Natal and San Cristobal from the SHADOZ network). Tropospheric ozone concentrations above the Andes are lower than ozone over San Cristobal and Natal for similar time periods. Ozone variability and pollution layers are also reduced in the troposphere above the Andes. We explain these differences in terms of reduced contributions from the boundary layer and from horizontal transport. In the tropical tropopause layer, ozone is well-mixed up to near the cold point tropopause level. In this regard, our profiles do not show constraints to deep mixing above 14 km, as has been consistently observed at other tropical stations. Total column ozone and stratospheric column ozone are comparable among the three sites. However, the contribution of tropospheric column ozone to total column ozone is significantly lower above the Andes. Our comparisons provide a connection between observations from tropical stations in equatorial South America separated by the wide continental mass. Identified differences in ozone throughout the atmospheric column demonstrate the global benefit of having an ozone sounding station at the equatorial Andes in support of global monitoring networks. 相似文献
58.
Long-term simulations of thermal and hydraulic characteristics in a mountain massif: The Mont Blanc case study, French and Italian Alps 总被引:3,自引:2,他引:1
The use of hydrothermal simulation models to improve the prediction of water inflows in underground works during drilling
is tested in the Mont Blanc tunnel, French and Italian Alps. The negative thermal anomaly that was observed during the drilling
of this tunnel in 1960 is reproduced by long-term, transient hydrothermal simulations. Sensitivity analysis shows the great
inertia of thermal phenomena at the massif scale. At the time of tunnel drilling, the massif had not reached thermal equilibrium.
Therefore, a set of simulation scenarios, beginning at the end of the last glacial period, was designed to explain the anomaly
encountered in the tunnel in 1960. The continuous cooling of alpine massifs due to infiltration of waters from the surface
has occurred for 12,000 years and is expected to continue for about 100,000 years. Comparisons of water-discharge rates simulated
in the tunnel with those observed indicate that this hydrothermal method is a useful tool for predicting water inflows in
underground works.
Received, May 1998 · Revised, March 1999 · Accepted, April 1999 相似文献
59.
Santiago Hernández-León Lutz Postel Javier Arístegui May Gómez María Fernanda Montero Santiago Torres Carlos Almeida Eugen Kühner Ullrich Brenning Eberhard Hagen 《Journal of Oceanography》1999,55(4):471-482
Plankton biomass and indices of metabolism and growth [electron transport system (ETS), glutamate dehydrogenase (GDH) and aspartate transcarbamylase (ATC) activities] were studied over a 2,800 km east-west section of the tropical North Atlantic Ocean (21°N) in <200, 200–500 and >;500 µm size classes. On the large-scale, zooplankton (>;200 µm) enzymatic activities increased westward in the study section, where large cyanobacteria chains (Trichodesmium spp.) were observed. Parallel to it, an increase in medium calanoids (1–2 mm length) was observed towards the western part of the transect, whereas small calanoids (<1 mm) were dominant throughout the boundary area of the subtropical gyre. Microplankton ETS and mesoplankton ETS and ATC activities seemed to match the wave length of low frequency waves. Our results suggest that such waves are related to the observed enhancement of metabolic activity of micro- and mesoplankton. The large-scale and mesoscale variability observed give evidence of the inadequacy of assuming a steady-state picture of the euphotic zone of tropical and subtropical waters. 相似文献
60.
Aina G. Gómez Bárbara Ondiviela María Fernández José A. Juanes 《Marine pollution bulletin》2017,114(1):239-246
An atlas of susceptibility to pollution of 320 Spanish marinas is provided. Susceptibility is assessed through a simple, fast and low cost empirical method estimating the flushing capacity of marinas. The Complexity Tidal Range Index (CTRI) was selected among eleven empirical methods. The CTRI method was selected by means of statistical analyses because: it contributes to explain the system's variance; it is highly correlated to numerical model results; and, it is sensitive to marinas' location and typology. The process of implementation to the Spanish coast confirmed its usefulness, versatility and adaptability as a tool for the environmental management of marinas worldwide. The atlas of susceptibility, assessed through CTRI values, is an appropriate instrument to prioritize environmental and planning strategies at a regional scale. 相似文献