Centro Andaluz Of Medio Ambiente Ceama

La Línea de la Concepción, Spain

Centro Andaluz Of Medio Ambiente Ceama

La Línea de la Concepción, Spain
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Puga-Bernabeu A.,University of Granada | Martin J.M.,University of Granada | Braga J.C.,University of Granada | Sanchez-Almazo I.M.,Centro Andaluz Of Medio Ambiente Ceama
Sedimentology | Year: 2010

During the Late Tortonian, platform-margin-prograding clinoforms developed at the south-western margin of the Guadix Basin. Large-scale wedge-shaped deposits here comprise 26 rhythms of mixed carbonate-siliciclastic bedset packages and marl beds. These sediments were deposited on a shallow-water, temperate-carbonate distally steepened ramp. A downslope-migrating sandwave field developed in this ramp, with sandwaves moving progressively down the ramp to the ramp-slope, where they destabilized, folded and occasionally collapsed. Downslope sandwave migration was induced by currents flowing basinwards. During the Late Tortonian, the Guadix Basin was open north to the Atlantic Ocean via the Dehesas de Guadix Strait and connected east to the Mediterranean Sea through the Almanzora Corridor. According to the proposed current circulation model for the Guadix Basin for this time, surface marine currents from the Atlantic entered the basin from the northern seaway. These currents moved counter-clockwise and shifted the sediment on the ramp, forming sandwaves that migrated downslope. The development of platform-margin prograding clinoforms by the basinward sediment-transport mechanisms inferred here is known relatively poorly in the ancient sedimentary record. Moreover, these wedge-shaped geometries are similar to those found in some shelves in the Western Mediterranean Sea and could represent an outcrop analogue to (sub)-recent, platform-margin clinoforms revealed by high-resolution seismic studies. © 2009 The Authors. Journal compilation © 2009 International Association of Sedimentologists.

Piedehierro A.A.,University of Extremadura | Anton M.,University of Extremadura | Cazorla A.,Centro Andaluz Of Medio Ambiente Ceama | Cazorla A.,University of Granada | And 4 more authors.
Atmospheric Research | Year: 2014

Among the factors affecting the solar radiation that reaches the ground, clouds play a key role in its short-term variability causing events ranging from almost total reduction to substantial enhancements under particular conditions. The purpose of this paper is to detect and to analyze the enhancement events on total solar horizontal irradiance at Granada (Southeastern Spain) using one-minute data during a study period of five years (January 2006 to December 2010). For this goal, an empirical model for cloud-free conditions has been used together with information on cloud cover (i.e., oktas) provided by a sky camera. Around 6% of the one-minute data were classified as enhancements, but only those episodes with duration longer than 5. min were studied. For all these episodes, the relative increases over the expected cloud-free values were, on average, 13.5%, reaching maximum values up to 50%. The enhancement episodes were related to broken-cloud situations (2-7. oktas) without prevalence for a particular number of oktas. The analysis of the seasonal distribution of those events showed that ~. 50% of them occur in spring, followed distantly by the other seasons with percentages below 20%. Additionally, a long enhancement event (74. min) was analyzed in detail, showing the relevant role of the diffuse component in this event. Finally, extreme enhancements (those episodes with surface solar levels higher than their extraterrestrial value) were also reported, consisting in 0.14% of the one-minute data. They occurred only under heavy cloudy situations (6-7. oktas), showing relative increases between 30% and 60% with respect to expected cloud-free conditions. © 2013 Elsevier B.V.

Reverter B.R.,University of Granada | Reverter B.R.,Centro Andaluz Of Medio Ambiente Ceama | Sanchez-Canete E.P.,CSIC - Estación Experimental De Zonas Áridas | Resco V.,Research Center del Fuego | And 4 more authors.
Biogeosciences | Year: 2010

Two years of continuous measurements of net ecosystem exchange (NEE) using the eddy covariance technique were made over a Mediterranean alpine shrubland. This ecosystem was found to be a net source of CO2 (+ 52 ± 7 g C m-2 and + 48 ± 7 g C m-2 for 2007 and 2008) during the two-year study period. To understand the reasons underlying this net release of CO2 into the atmosphere, we analysed the drivers of seasonal variability in NEE over these two years. We observed that the soil water availability - driven by the precipitation pattern - and the photosynthetic photon flux density (PPFD) are the key factors for understanding both the carbon sequestration potential and the duration of the photosynthetic period during the growing season. Finally, the effects of the self-heating correction to CO2 and H2O fluxes measured with the open-path infrared gas analyser were evaluated. Applying the correction turned the annual CO2 budget in 2007 from a sink (-135 ± 7 g C m -2) to a source (+ 52 ± 7 g C m-2). The magnitude of this change is larger than reported previously and is shown to be due to the low air density and cold temperatures at this high elevation study site. © Author(s) 2010.

Roman R.,University of Valladolid | Anton M.,University of Extremadura | Valenzuela A.,Centro Andaluz Of Medio Ambiente Ceama | Gil J.E.,Centro Andaluz Of Medio Ambiente Ceama | And 9 more authors.
Tellus, Series B: Chemical and Physical Meteorology | Year: 2013

This paper presents a study of a strong desert dust episode over the Iberian Peninsula, and its effect on the spectral ultraviolet (UV) irradiance in Granada, Spain. Remote sensing measurements, forecast models, and synoptic analysis are used to identify a Saharan desert dust outbreak that affected the Iberian Peninsula starting 20 July 2009. Additionally, a Bentham DMc150 spectroradiometer is employed to obtain global, direct and diffuse spectral UV irradiances every 15 minutes in Granada. The desert dust caused a large attenuation of the direct UV irradiance (up to 55%), while the diffuse UV irradiance increased up to 40% at 400 nm. The UVSPEC/LibRadtran radiative transfer model is used to study the spectral dependence of the experimental UV irradiance ratios (ratios of spectral irradiance for the day with the highest aerosol load to that measured in days with low-moderate load). The spectral increase or decrease of the UV direct irradiance ratios depends on a new parameter: a threshold wavelength. The spectral dependence of the UV diffuse irradiance ratio can be explained because under the influence of the intense dust outbreak, the Mie scattering by aerosols at shorter wavelengths is stronger than the Rayleigh scattering by gases. Finally, the sensitivity analysis of the aerosol absorption properties shows a substantial attenuation of UV spectral irradiance with a weak spectral dependence. © R. Román et al.

Mladenov N.,University of Granada | Alados-Arboledas L.,Centro Andaluz Of Medio Ambiente Ceama | Alados-Arboledas L.,University of Granada | Olmo F.J.,Centro Andaluz Of Medio Ambiente Ceama | And 5 more authors.
Atmospheric Environment | Year: 2011

Understanding the chemical character of organic aerosols is extremely important for evaluating their role in climate forcing and human respiratory health. Aerosol columnar properties retrieved by sun photometry represent a large dataset of information about the physical and light absorbing and scattering properties of the total aerosol, but lack more detailed chemical information about the organic fraction of atmospheric particulate matter. To obtain additional information about relationships between organic aerosol sources and columnar properties, we simultaneously examined stable isotope properties of PM10 aerosols from urban (Granada, Spain) and remote (Sierra Nevada, Spain) sites and diesel exhaust, spectroscopic properties of water soluble organic carbon (WSOC) of PM10 aerosols, and sun photometry measurements. We demonstrated that C and N stable isotopes and parameters from UV-vis and fluorescence spectroscopy are able to discriminate between aerosols receiving substantial fossil fuel pollution and those influenced by Saharan dust in an urban area. More depleted δ13C was associated with low asymmetry parameter, gλ, and high values of the spectral slope ratio, SR, were associated with high effective radius, typical of pollution situations. The humification index (HIX), used predominantly to evaluate the degree of organic matter humification, was significantly related to gλ and the radius of fine mode particles, rf, and may reflect aging of the Saharan dust-influenced aerosols. Parallel factor analysis (PARAFAC) modeling identified a fluorescent component (C3) with a spectrum similar to that of naphthalene, which was significantly related to gλ and rf. The diesel exhaust sample represented a pollution end-member, with the lightest δ13C value (-26.4‰), lowest SR (0.95), lowest HIX (2.77) and highest %C3 (20%) of all samples. © 2011 Elsevier Ltd.

Cuezva S.,CSIC - National Museum of Natural Sciences | Fernandez-Cortes A.,CSIC - National Museum of Natural Sciences | Benavente D.,University of Alicante | Serrano-Ortiz P.,CSIC - Estación Experimental De Zonas Áridas | And 3 more authors.
Atmospheric Environment | Year: 2011

This study tests the hypothesis that the degree of moisture in the soil pore system determines gas exchange processes (ventilation/charge) between the outer atmosphere and the karst-epikarst during the warm, dry period (summer). These processes explain " anomalous" CO2 fluxes measured over this and other ecosystems. Emission of CO2 by ventilation of cavities requires an open double membrane system (host rock and soil) through which air movement can take place (H2Ovapour, CO2, 222Rn, etc.). An experimental study on the behavior of the soil and host rock porous system under changing air humidity conditions, coupled with a broad analytical approach addressing CO2 fluxes using the eddy-covariance technique and monitoring of the cave microclimate serves to define the suitable environmental conditions favoring air transfer between the cave atmosphere and exterior. This study shows the correlation between evapotranspiration, CO2 emissions, and cave ventilation processes due to the daytime opening of the soil membrane. Thus, the role of the soil as a membrane/interface or transfer medium can be observed, and it is directly dependent on weather conditions (temperature, humidity, wind). © 2010 Elsevier Ltd.

Kowalski A.S.,University of Granada | Kowalski A.S.,Centro Andaluz Of Medio Ambiente Ceama | Argueso D.,University of Granada
Tellus, Series B: Chemical and Physical Meteorology | Year: 2011

The advection-diffusion equations defining control volume conservation laws in micrometeorological research are analysed to resolve discrepancies in their appropriate scalar variables for heat and mass transport. A scalar variable that is conserved during vertical motions enables the interpretation of turbulent mixing as 'diffusion'. Gas-phase heat advection is shown to depend on gradients in the potential temperature (θ), not the temperature (T). Since conduction and radiation depend on T, advection-diffusion of heat depends on gradients of both θ and T. Conservation of θ (the first Law of Thermodynamics) requires including a pressure covariance term in the definition of the turbulent heat flux. Mass advection and diffusion are universally agreed to depend directly on gradients in the gas 'concentration' (c), a nonetheless ambiguous term. Depending upon author, c may be defined either as a dimensionless proportion or as a dimensional density, with non-trivial differences for the gas phase. Analyses of atmospheric law, scalar conservation and similarity theory demonstrate that mass advection-diffusion in gases depends on gradients, not in density but rather in a conserved proportion. Flux-tower researchers are encouraged to respect the meteorological tradition of writing conservation equations in terms of scalar variables that are conserved through simple air motions. © 2011 The Authors Tellus B © 2011 John Wiley & Sons A/S.

Sanchez-Canete E.P.,EEZA CSIC | Sanchez-Canete E.P.,Centro Andaluz Of Medio Ambiente Ceama | Kowalski A.S.,Centro Andaluz Of Medio Ambiente Ceama | Kowalski A.S.,University of Granada | And 5 more authors.
Biogeosciences | Year: 2013

Knowledge of all the mechanisms and processes involved in soil CO2 emissions is essential to close the global carbon cycle. Apart from molecular diffusion, the main physical component of such CO2 exchange is soil ventilation. Advective CO2 transport, through soil or snow, has been correlated with the wind speed, friction velocity or pressure (p). Here we examine variations in subterranean CO2 molar fractions (χc) over two years within a vertical profile (1.5 m) in a semiarid ecosystem, as influenc. © 2013 Author(s).

Roman R.,University of Valladolid | Anton M.,Centro Andaluz Of Medio Ambiente Ceama | Anton M.,University of Granada | Cazorla A.,Centro Andaluz Of Medio Ambiente Ceama | And 8 more authors.
Atmospheric Measurement Techniques | Year: 2012

This paper proposes a method to obtain spectral sky radiances, at three wavelengths (464, 534 and 626 nm), from hemispherical sky images. Images are registered with the All-Sky Imager installed at the Andalusian Center for Environmental Research (CEAMA) in Granada (Spain). The methodology followed in this work for the absolute calibration in radiance of this instrument is based on the comparison of its output measurements with modelled sky radiances derived from the LibRadtran/UVSPEC radiative transfer code under cloud-free conditions. Previously, in order to check the goodness of the simulated radiances, these are compared with experimental values recorded by a CIMEL sunphotometer. In general, modelled radiances are in agreement with experimental data, showing mean differences lower than 20% except for the pixels located next to the Sun position that show larger errors. The relationship between the output signal of the All-Sky Imager and the modelled sky radiances provides a calibration matrix for each image. The variability of the matrix coefficients is analyzed, showing no significant changes along a period of 5 months. Therefore, a unique calibration matrix per channel is obtained for all selected images (a total of 705 images per channel). Camera radiances are compared with CIMEL radiances, finding mean absolute differences between 2% and 15% except for pixels near to the Sun and high scattering angles. We apply these calibration matrices to three images in order to study the sky radiance distributions for three different sky conditions: cloudless, overcast and partially cloudy. Horizon brightening under cloudless conditions has been observed together with the enhancement effect of individual clouds on sky radiance. © 2012 Author(s).

Valenzuela A.,University of Granada | Valenzuela A.,Centro Andaluz Of Medio Ambiente Ceama | Olmo F.J.,University of Granada | Olmo F.J.,Centro Andaluz Of Medio Ambiente Ceama | And 7 more authors.
Atmospheric Chemistry and Physics | Year: 2012

The daily (24 h) averages of the aerosol radiative forcing (ARF) at the surface and the top of the atmosphere (TOA) were calculated during desert dust events over Granada (southeastern Spain) from 2005 to 2010. A radiative transfer model (SBDART) was utilized to simulate the solar irradiance values (0.31-2.8 μm) at the surface and TOA, using as input aerosol properties retrieved from CIMEL sun photometer measurements via an inversion methodology that uses the sky radiance measurements in principal plane configuration and a spheroid particle shape approximation. This inversion methodology was checked by means of simulated data from aerosol models, and the derived aerosol properties were satisfactorily compared against well-known AERONET products. Good agreement was found over a common spectral interval (0.2-4.0 μm) between the simulated SBDART global irradiances at surface and those provided by AERONET. In addition, simulated SBDART solar global irradiances at the surface have been successfully validated against CM-11 pyranometer measurements. The comparison indicates that the radiative transfer model slightly overestimates (mean bias of 3%) the experimental solar global irradiance. These results show that the aerosol optical properties used to estimate ARF represent appropriately the aerosol properties observed during desert dust outbreak over the study area. The ARF mean monthly values computed during desert dust events ranged from-13 ± 8 W m -2 to-34 ± 15 W m -2 at surface, from-4 ± 3 W m -2 to-13 ± 7 W m -2 at TOA and from +6 ± 4 to +21 ± 12 W m -2 in the atmosphere. We have checked if the differences found in aerosol optical properties among desert dust sectors translate to differences in ARF. The mean ARF at surface (TOA) were-20 ± 12 (-5 ± 5) W m -2,-21 ± 9 (-7 ± 5) W m -2 and-18 ± 9 (-6 ± 5) W m -2 for sector A (northern Morocco; northwestern Algeria), sector B (western Sahara, northwestern Mauritania and southwestern Algeria), and sector C (eastern Algeria, Tunisia), respectively. The Kolmogorov-Smirnov statistical test revealed that daily {ARF} values at TOA for sector A were significantly different from the other two sectors, likely as a result of the lower values of single scattering albedo obtained for sector A. The mean values of aerosol radiative forcing efficiency at surface (TOA) were-74 ± 12 W m -2 (-17 ± 7 W m -2) for sector A,-70 ± 14 W m -2 (-20 ± 9 W m -2) for sector B, and-65 ± 16 W m -2 (-22 ± 10 W m -2) for sector C, and thus comparable between the three sectors in all seasons. © 2012 Author(s).

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