276 research outputs found
A new empirical model to estimate hourly diffuse photosynthetic photon flux density
No full textThis is a preprint version of a paper accepted to be published in "Foyo-Moreno, I.; Alados-Arboledas, I.; Alados-Arboledas, L. A new empirical model to estimate hourly diffuse photosynthetic photon flux density. Atmospheric Research, 203: 189-196 (2018)", doi: https://doi.org/10.1016/j.atmosres.2017.12.012Knowledge of the photosynthetic photon flux density (Qp) is critical in different applications dealing with climate change, plant physiology, biomass production, and natural illumination in greenhouses. This is particularly true regarding its diffuse component (Qpd), which can enhance canopy light-use efficiency and thereby boost carbon uptake. Therefore, diffuse photosynthetic photon flux density is a key driving factor of ecosystem-productivity models. In this work, we propose a model to estimate this component, using a previous model to calculate Qp and furthermore divide it into its components. We have used measurements in urban Granada (southern Spain), of global solar radiation (Rs) to study relationships between the ratio Qpd/Rs with different parameters accounting for solar position, water-vapour absorption and sky conditions. The model performance has been validated with experimental measurements from sites having varied climatic conditions. The model provides acceptable results, with the mean bias error and root mean square error varying between − 0.3 and − 8.8% and between 9.6 and 20.4%, respectively.This work was supported by the Andalusia Regional Government project P12-RNM-2409, by the Spanish Ministry of Economy and Competitiveness projects CGL2013-45410-R and CGL2016-81092-R, and by the European Union's Horizon 2020 research and innovation programme project ACTRIS-2 (grant agreement No 654109)
A new conventional regression model to estimate hourly photosynthetic photon flux density under all sky conditions
No full text"This is the pre-peer reviewed version of the following article: Foyo-Moreno, I., Alados, I. and Alados-Arboledas, L. (2017), A new conventional regression model to estimate hourly photosynthetic photon flux density under all sky conditions. Int. J. Climatol.. doi:10.1002/joc.5063, which has been published in final form at hppt://dx.doi.org/10.1002/joc.5063 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."In this work we propose a new and simple empirical model to estimate photosynthetic photon flux density under all sky conditions, developed using experimental measurements carried out at Granada, an urban site in Southeastern Spain during two recent years (2014-2015). The model uses the solar zenith angle and clearness index as input parameters, and thus needs only global irradiance measurements usually registered in most radiometric networks. Five stations located in the northern and southern hemisphere with different climatological characteristics at Europe, Asia and America (Spain, Japan and Argentina) were used to validate the model. The model provides satisfactory results, giving low mean bias error for all stations, particularly Mean Bias Error, MBE, being less than 1% in absolute values in three stations and Root Mean Square Error, RMSE, below 6% for all stations except one with 6.1%. These results show better accuracy in comparison to other earlier empirical models and suggest the effectiveness of the model by its general applicability.Andalusia Regional Government. Grant Numbers: P11-RNM-7186, P12-RNM-2409Spanish Ministry of Economy and Competitiveness. Grant Numbers: CGL2016-81092-R, CGL2013-45410-R, CGL2014-52838-C2-1-REuropean Union's Horizon 2020 Research And Innovation Programme. Grant Number: 65410
Four-dimensional distribution of the 2010 Eyjafjallajökull volcanic cloud over Europe observed by EARLINET
No full textThe eruption of the Icelandic volcano Eyjafjallajökull in April–May 2010 represents a "natural experiment" to study the impact of volcanic emissions on a continental scale. For the first time, quantitative data about the presence, altitude, and layering of the volcanic cloud, in conjunction with optical information, are available for most parts of Europe derived from the observations by the European Aerosol Research Lidar NETwork (EARLINET). Based on multi-wavelength Raman lidar systems, EARLINET is the only instrument worldwide that is able to provide dense time series of high-quality optical data to be used for aerosol typing and for the retrieval of particle microphysical properties as a function of altitude. In this work we show the four-dimensional (4-D) distribution of the Eyjafjallajökull volcanic cloud in the troposphere over Europe as observed by EARLINET during the entire volcanic event (15 April–26 May 2010). All optical properties directly measured (backscatter, extinction, and particle linear depolarization ratio) are stored in the EARLINET database available at http://www.earlinet.org. A specific relational database providing the volcanic mask over Europe, realized ad hoc for this specific event, has been developed and is available on request at http://www.earlinet.org. During the first days after the eruption, volcanic particles were detected over Central Europe within a wide range of altitudes, from the upper troposphere down to the local planetary boundary layer (PBL). After 19 April 2010, volcanic particles were detected over southern and south-eastern Europe. During the first half of May (5–15 May), material emitted by the Eyjafjallajökull volcano was detected over Spain and Portugal and then over the Mediterranean and the Balkans. The last observations of the event were recorded until 25 May in Central Europe and in the Eastern Mediterranean area. The 4-D distribution of volcanic aerosol layering and optical properties on European scale reported here provides an unprecedented data set for evaluating satellite data and aerosol dispersion models for this kind of volcanic events
Optical and microphysical properties of fresh biomass burning aerosol retrieved by Raman lidar, and star-and sun-photometry
No full textA fresh biomass-burning pollution plume was monitored and characterized in terms of optical and microphysical properties for the first time with a combination of Raman lidar and star- and sun-photometers. Such an instrument combination is highly useful for 24-h monitoring of pollution events. The observations were made at Granada (37.16 degrees N, 3.6 degrees W), Spain. The fresh smoke particles show a rather pronounced accumulation mode and features markedly different from those reported for aged particles. We find lidar ratios around 60-65 sr at 355 nm and 532 nm, and particle effective radii below 0.20 mu m. We find low values of the single-scattering albedo of 0.76-0.9 depending on measurement wavelength. The numbers are lower than what have been found for aged, long-range-transported smoke that originated from boreal fires in Canada and Siberia. Citation: Alados-Arboledas, L., D. Muller, J. L. Guerrero-Rascado, F. Navas-Guzman, D. Perez-Ramirez, and F. J. Olmo (2011), Optical and microphysical properties of fresh biomass burning aerosol retrieved by Raman lidar, and star- and sun-photometry, Geophys. Res. Lett., 38, L01807, doi:10.1029/2010GL045999
A comparison of the columnar aerosol physical parameters retrieved by different methods at INDALO-2003
No full textAbstract European Aerosol Conferenc
Extreme ultraviolet index due to broken clouds at a midlatitude site, Granada (southeastern Spain)
No full textCloud cover usually attenuates the ultraviolet (UV) solar radiation but, under certain sky conditions, the clouds may produce an enhancement effect increasing the UV levels at surface. The main objective of this paper is to analyze an extreme UV enhancement episode recorded on 16 June 2009 at Granada (southeastern Spain). This phenomenon was characterized by a quick and intense increase in surface UV radiation under broken cloud fields (5-7oktas) in which the Sun was surrounded by cumulus clouds (confirmed with sky images). Thus, the UV index (UVI) showed an enhancement of a factor 4 in the course of only 30min around midday, varying from 2.6 to 10.4 (higher than the corresponding clear-sky UVI value). Additionally, the UVI presented values higher than 10 (extreme erythemal risk) for about 20min running, with a maximum value around 11.5. The use of an empirical model and the total ozone column (TOC) derived from the Global Ozone Monitoring Experiment (GOME) for the period 1995-2011 showed that the value of UVI~11.5 is substantially larger than the highest index that could origin the natural TOC variations over Granada. Finally, the UV erythemal dose accumulated during the period of 20min with the extreme UVI values under broken cloud fields was 350J/m 2 which surpass the energy required to produce sunburn of the most human skin types.Fil: Antón, M.. Universidad de Granada; EspañaFil: Piedehierro, A. A.. Universidad de Extremadura; EspañaFil: Alados Arboledas, L.. Universidad de Granada; EspañaFil: Wolfram, Elian Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Olmo, F. J.. Universidad de Granada; Españ
Eruption of the Eyjafjallajokull Volcano in spring 2010 : Multiwavelength Raman lidar measurements of sulphate particles in the lower troposphere
No full textA fraction of the volcanic plume that originated from the Eyjafjallajokull volcanic eruption on Iceland in 2010 reached the southern Iberian Peninsula in May 2010. The plume was monitored and characterized in terms of optical and microphysical properties with a combination of Raman lidar and star- and Sun-photometers. Our observations showed that the plume arriving at the Iberian Peninsula was mainly composed of sulphate and sulphuric-acid particles. To our knowledge, this is the first study of optical properties and inverted microphysical properties of volcanic sulphate particles in the lower troposphere/boundary layer based on multiwavelength Raman lidar measurements. A remarkable increase in the particle number concentration in the accumulation mode was determined from the inversion of the aerosol optical properties. The large Angstrom exponents and low linear particle depolarization ratios (4-7%) indicated the presence of small and spherical particles. The particle effective radii ranged between 0.30 and 0.55 mu m. In situ instrumentation confirmed an increase of sulphate particles at ground level during this period. Citation: Navas-Guzman, F., D. Muller, J. A. Bravo-Aranda, J. L. Guerrero-Rascado, M. J. Granados-Munoz, D. Perez-Ramirez, F. J. Olmo, and L. Alados-Arboledas (2013), Eruption of the Eyjafjallajokull Volcano in spring 2010: Multiwavelength Raman lidar measurements of sulphate particles in the lower troposphere, J. Geophys. Res. Atmos., 118, 1804-1813, doi:10.1002/jgrd.50116
Aerosol optical properties in a rural site ofSouth Italy from simultaneous measurements by CIMEL and Avantes radiometers
No full textAssimilation of humidity and temperature observations retrieved from ground-based microwave radiometers into a convective-scale NWP model
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