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1.
R. Nieto L. Gimeno J. A. Añel L. De la Torre D. Gallego D. Barriopedro M. Gallego A. Gordillo A. Redaño G. Delgado 《Meteorology and Atmospheric Physics》2007,96(1-2):103-119
Summary The Iberian Peninsula is one of the regions in the world with higher occurrence of cut-off low systems (COL). The aim of this
paper is to analyse the weather events (rainfall and cloudiness layer) associated to COLs in the Iberian Peninsula with tools
not previously used: (a) the use of the new multidecadal COLs database developed by Nieto et al (2005) that permit us to study
a 41 years period (1958–1998), (b) the checking of the expected weather events (rainfall and cloudiness layer) associated
with COLs in a conceptual model (Winkler et al, 2005) and (c) the extensive use of radiosoundings to analyse convective instability
in areas inside and close to the COL. Two points of view are used to make the analysis: (1) a source oriented method, when
a particular COL is followed and its associated precipitation and cloudiness is analysed over four quadrants in which Iberia
was divided and (2) a receptor oriented method, when the precipitation associated to COLs is analysed in given areas, defined
by patterns of precipitation. Results reveal that the precipitation and cloudiness patterns associated to COLs in the conceptual
model reproduce quite well the main characteristics found over the Iberian Peninsula. The generalized idea that most of the
COLs produce intense convective rainfall is show to be misleading. Convective phenomena are important usually when the centre
of the COL is located on the Mediterranean region. Most of the rainfall associated with COLs comes from the baroclinic shield;
specially in cases located over the west half of the Iberian Peninsula. It is shown that nearly 30% of COLs do not induce
any rainfall; most of them located in the southern half of the Peninsula, and mainly during autumn. Only 30% of COLs produce
generalized rainfall over the whole analysed territory, being most of them (about 90%) located over the western half of the
Iberian Peninsula. 相似文献
2.
A description of how metal pollution occurs in the Tinto-Odiel rias (Huelva-Spain) through the application of cluster analysis 总被引:3,自引:0,他引:3
In the last few decades, the study of space-time distribution and variations of heavy metals in estuaries has been extensively studied as an environmental indicator. In the case described here, the combination of acid water from mines, industrial effluents and sea water plays a determining role in the evolutionary process of the chemical makeup of the water in the estuary of the Tinto and Odiel Rivers, located in the southwest of the Iberian Peninsula.Based on the statistical treatment of the data from the analysis of the water samples from this system, which has been affected by processes of industrial and mining pollution, the 16 variables analyzed can be grouped into two large families. Each family presents high, positive Pearson r values that suggest common origins (fluvial or sea) for the pollutants present in the water analyzed and allow their subsequent contrast through cluster analysis. 相似文献
3.
Laser-based validation of GLONASS orbits by short-arc technique 总被引:1,自引:0,他引:1
F. Barlier C. Berger P. Bonnefond P. Exertier O. Laurain J. F. Mangin J. M. Torre 《Journal of Geodesy》2001,75(11):600-612
The International GLONASS Experiment (IGEX-98) was carried out between 19 October 1998 and 19 April 1999. Among several objectives
was the precise orbit determination of GPS and GLONASS satellites and its validation by laser ranging observations. Local
laser-based orbit corrections (radial, tangential and normal components in a rotating orbital local reference frame) are computed
using a geometrical short-arc technique. The order of magnitude of these corrections is at the level of few decimeters, depending
on the considered components. The orbit corrections are analyzed as a function of several parameters (date, orbital plane,
geographical area). The mean corrections are at the level of several centimeters. However, when averaging over the entire
campaign and for all the satellites, no mean radial, tangential and normal orbit corrections are found. The origin of the
observed corrections is considered (errors due to the geocentric gravitational constant, the non-gravitational forces, the
thermal equilibrium of on-board equipment, the reference systems, the location and the signature of the retroreflector array,
and the precision of the satellite laser ranges). Some features are also due to errors in the radio-tracking GLONASS orbits.
Further investigations will be needed to better understand the origin of various biases.
Received: 17 February 2000 / Accepted: 31 January 2001 相似文献
4.
5.
Hydrological processes of lowland watersheds of the southern USA are not well understood compared to a hilly landscape due to their unique topography, soil compositions, and climate. This study describes the seasonal relationships between rainfall patterns and runoff (sum of storm flow and base flow) using 13 years (1964–1976) of rainfall and stream flow data for a low‐gradient, third‐order forested watershed. It was hypothesized that runoff–rainfall ratios (R/P) are smaller during the dry periods (summer and fall) and greater during the wet periods (winter and spring). We found a large seasonal variability in event R/P potentially due to differences in forest evapotranspiration that affected seasonal soil moisture conditions. Linear regression analysis results revealed a significant relationship between rainfall and runoff for wet (r2 = 0·68; p < 0·01) and dry (r2 = 0·19; p = 0·02) periods. Rainfall‐runoff relationships based on a 5‐day antecedent precipitation index (API) showed significant (r2 = 0·39; p < 0·01) correspondence for wet but not (r2 = 0·02; p = 0·56) for dry conditions. The same was true for rainfall‐runoff relationships based on 30‐day API (r2 = 0·39; p < 0·01 for wet and r2 = 0·00; p = 0·79 for dry). Stepwise regression analyses suggested that runoff was controlled mainly by rainfall amount and initial soil moisture conditions as represented by the initial flow rate of a storm event. Mean event R/P were higher for the wet period (R/P = 0·33), and the wet antecedent soil moisture condition based on 5‐day (R/P = 0·25) and 30‐day (R/P = 0·26) prior API than those for the dry period conditions. This study suggests that soil water status, i.e. antecedent soil moisture and groundwater table level, is important besides the rainfall to seasonal runoff generation in the coastal plain region with shallow soil argillic horizons. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
6.
AbstractThe objectives of this study were to discover the relationship between variables in a water reservoir and the hydrochemical variations related to acid mine drainage (AMD), and to describe the horizontal stratification related to vertical salinity and variations in metals present in the region. The information obtained may be used for establishing risk evaluation criteria and to design future remediation strategies, which could be useful for new dams. The hydrochemical characterization was based on a sampling campaign performed in October 2011. A total of 28 samples, at 1-m-deep intervals, were obtained. The hydrogeochemical study of the polluted reservoir shows that the dilution effect is not sufficient to neutralize AMD contributions from mining activity. Sampling carried out from the surface water to the deepest points reveals stratification of the reservoir that allows it to be included in the group of monomictic and holomitic lakes.
Editor D. Koutsoyiannis; Associate editor M.D. Fidelibus 相似文献
7.
Is geographical proximity necessary in the innovation networks in the era of global economy? 总被引:7,自引:0,他引:7
In the analysis of geographical spillovers, a commonly accepted hypothesis is that the different actors of innovation need to be physically closed to one another because the transfer of tacit knowledge implies frequent face-to-face relations. This hypothesis is put under closer examination in this paper. The first section analyses the need for economic agents to be closely located to develop research and innovative activities, starting with the analysis of their need for co-ordination and using some case studies. Based on the example of three French regions, the second section examines the importance given by the local development policies to geographical proximity in order to support the rapid development of local networks favouring innovation. In both sections, nonlocal relations appear as a key factor to develop innovation. As a conclusion, nonlocal relations should be encouraged by local development policies in the same way as local relations. 相似文献
8.
Ribera P. Gimeno L. Gallego D. García-Herrera R. Hernández E. de la Torre L. Nieto R. Calvo N. 《Studia Geophysica et Geodaetica》2004,48(2):447-458
Two different groups of indices have been defined to analyze the evolution of global temperature between 1958 and 1998. All the indices were evaluated at three different levels (850, 500 and 200 hPa), and averaged indices were calculated using the whole globe, continental areas and oceanic areas. The first group of indices analyzes the area of the world covered with higher and lower than normal temperatures, detecting a slight cooling in the 200 hPa level. The second group of indices studies the annual frequency of extreme events, and again, it is at 200 hPa where the most intense variation is detected. Finally, an analysis is performed to determine the regions most sensible to variations in the occurrence of extreme events. Tropical areas are mostly responsible of the variations detected in the second group of indices. 相似文献
9.
Ribera P. Gallego D. Gimeno L. Perez-Campos J.F. García-Herrera R. Hernández E. de la Torre L. Nieto R. Calvo N. 《Studia Geophysica et Geodaetica》2004,48(2):459-468
Equivalent temperature based in the NCEP/NCAR reanalysis database has been used as a simultaneous measure of temperature and humidity. Its variations during the 1958-1998 added to the effect of the inclusion of satellite data during the late seventies have been analyzed. An increase of the globally averaged equivalent temperature has been detected, the trend has been considerably greater during the first half of the study period and significant differences can be found between continental and oceanic areas. The relation of the trend with four of the main modes of climate variability has been assessed. The North Atlantic Oscillation and the Artic Oscillations are closely related to the equivalent temperature over the North Atlantic basin, extending toward Northern Asia in the second case. El Niño/Southern Oscillation and the Antarctic Oscillation seem to have a more global effect. 相似文献
10.
J. Aroba J. A. Grande J. M. Andújar M. L. de la Torre J. C. Riquelme 《Environmental Geology》2007,53(1):135-145
In this article, a set of clustering algorithms based on Fuzzy Logic and Data Mining are applied, allowing to obtain data
in the form of linguistic rules and charts about the behaviour of the Tinto and Odiel river estuary (SW Spain) affected by
Acid Mine Drainage (AMD). In order to provide researchers with no skills on data mining techniques an easy and intuitive interpretation,
we have developed a computer tool based on fuzzy logic that allows immediate qualitative analysis of the data contained in
a data from the estuary water chemical analyses, and serves as a contrast to functioning models previously proposed with classical
statistics. 相似文献