Andalusian Institute for Earth System Research IISTA

Granada, Spain

Andalusian Institute for Earth System Research IISTA

Granada, Spain
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Perez-Ramirez D.,University of Granada | Perez-Ramirez D.,Andalusian Institute for Earth System Research IISTA | Lyamani H.,University of Granada | Lyamani H.,Andalusian Institute for Earth System Research IISTA | And 10 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2016

This work focuses on the statistical analysis of day and night hourly pattern of columnar aerosol properties. To that end, we use the large database of star-photometry measurements at the University of Granada station (37.16°N, 3.60°W, 680 m a.s.l; South-East of Spain) for nighttime characterization, and co-located AERONET measurements for the daytime. The aerosol properties studied are the aerosol optical depth (AOD), Angstrom parameter (α(440-870)), aerosol optical depths of fine (AODfine) and coarse mode (AODcoarse) through the Spectral Deconvolution Algorithm (SDA). Microphysical properties are calculated by inverting AOD spectra and include the effective radius (reff) and volume concentration (V) of the total size distribution, and also the effective radius of the fine mode (rfine). The initial analysis for the different air masses that reach the study area reveals that generally day and night values of AOD and α(440-870) are not different statistically. Nighttime values of AODfine, reff and rfine do however, present larger values. The influence of North African air masses is remarkable both during the day and night, with high particle loads and low values of the Angstrom parameters and also with large contribution of coarse particles as AODcoarse and reff values are almost the double than for other air masses. The analyses of day-to-night hourly values reveal an increase in AOD, AODfine and AODcoarse during the day and a decrease during the night. Such a pattern could be explained by the different emission rates, accumulation, aging and deposition of particles. Changes in particle radius are also observed as part of the day-tonight particle evolution process, being rfine variations important mainly at daytime while for reff variations are more important at nighttime. Results of day-to-night evolution were found to be independent of air mass origin, and seem to be mainly associated with local processes. © 2016 SPIE.

Navas-Guzman F.,University of Granada | Navas-Guzman F.,Andalusian Institute for Earth System Research IISTA | Navas-Guzman F.,University of Bern | Bravo-Aranda J.A.,University of Granada | And 7 more authors.
Tellus, Series B: Chemical and Physical Meteorology | Year: 2013

In this work, a statistical study of aerosol optical properties retrieved from Raman lidar profiles has been addressed at the EARLINET station of Granada, Spain, during the period 2008-2010. Lidar measurements were performed during day- and night-time. Mean values and variances of the aerosol extinction and backscatter coefficient profiles in the troposphere have been computed. These profiles evidenced that during autumn-winter, most of the particles are confined to the first kilometres above the surface (below 3500 m above sea level), while a major presence of aerosol at higher altitudes is observed during spring-summer. Moreover, a study of the planetary boundary layer (PBL) height and aerosol stratification has been performed for the whole studied period. Monthly mean β-related Angström exponent values have been obtained for aerosols in the PBL and in the free troposphere. Furthermore, monthly mean lidar ratio values at 532 nm have been retrieved from Raman profiles during night-time. A detailed study of these intensive properties has allowed characterizing the aerosol present over our station. The results evidenced a predominance of large and scattering particles during spring and summer and an increase of small and absorbing particles during autumn and winter. © 2013 F. Navas-guzmán et al.

Perez-Ramirez D.,NASA | Perez-Ramirez D.,University of Granada | Perez-Ramirez D.,Universities Space Research Association | Whiteman D.N.,NASA | And 9 more authors.
Journal of Geophysical Research: Atmospheres | Year: 2014

In this paper we present comparisons of Aerosol Robotic Network (AERONET) precipitable water vapor (W) retrievals from Sun photometers versus radiosonde observations and other ground-based retrieval techniques such as microwave radiometry (MWR) and GPS. The comparisons make use of the extensive measurements made within the U.S. Department of Energy Atmospheric Radiation Measurement Program (ARM), mainly at their permanent sites located at the Southern Great Plains (Oklahoma, U.S.), Nauru Islands, and Barrow (Alaska, U.S.). These places experience different types of weather which allows the comparison of W under different conditions. Radiosonde and microwave radiometry data were provided by the ARM program while the GPS data were obtained from the SOUMINET network. In general, W obtained by AERONET is lower than those obtained by MWR and GPS by ∼6.0-9.0% and ∼6.0-8.0%, respectively. The AERONET values are also lower by approximately 5% than those obtained from the numerous balloon-borne radiosondes launched at the Southern Great Plains. These results point toward a consistent dry bias in the retrievals of W by AERONET of approximately 5-6% and a total estimated uncertainty of 12-15%. Differences with respect to MWR retrievals are a function of solar zenith angle pointing toward a possible bias in the MWR retrievals. Finally, the ability of AERONET precipitable water vapor retrievals to provide long-term records of W in diverse climate regimes is demonstrated. ©2014. American Geophysical Union. All Rights Reserved.

Perez-Ramirez D.,NASA | Perez-Ramirez D.,Universities Space Research Association | Perez-Ramirez D.,University of Granada | Veselovskii I.,RAS A.M. Prokhorov General Physics Institute | And 10 more authors.
Atmospheric Measurement Techniques | Year: 2015

This work deals with the applicability of the linear estimation technique (LE) to invert spectral measurements of aerosol optical depth (AOD) provided by AERONET CIMEL sun photometers. The inversion of particle properties using only direct-sun AODs allows the evaluation of parameters such as effective radius (reff) and columnar volume aerosol content (V) with significantly better temporal resolution than the operational AERONET algorithm which requires both direct sun and sky radiance measurements. Sensitivity studies performed demonstrate that the constraints on the range of the inversion are very important to minimize the uncertainties, and therefore estimates of reff can be obtained with uncertainties less than 30% and of V with uncertainties below 40 %. The LE technique is applied to data acquired at five AERONET sites influenced by different aerosol types and the retrievals are compared with the results of the operational AERONET code. Good agreement between the two techniques is obtained when the fine mode predominates, while for coarse mode cases the LE results systematically underestimate both reff and V. The highest differences are found for cases where no mode predominates. To minimize these biases, correction functions are developed using the multi-year database of observations at selected sites, where the AERONET retrieval is used as the reference. The derived corrections are tested using data from 18 other AERONET stations offering a range of aerosol types. After correction, the LE retrievals provide better agreement with AERONET for all the sites considered. Finally, the LE approach developed here is applied to AERONET and star-photometry measurements in the city of Granada (Spain) to obtain day-to-night time evolution of columnar aerosol microphysical properties. © Author(s) 2015.

Navas-Guzman F.,University of Granada | Navas-Guzman F.,Andalusian Institute for Earth System Research IISTA | Navas-Guzman F.,University of Bern | Fernandez-Galvez J.,University of Granada | And 9 more authors.
Atmospheric Measurement Techniques | Year: 2014

In this paper, we outline an iterative method to calibrate the water vapour mixing ratio profiles retrieved from Raman lidar measurements. Simultaneous and co-located radiosonde data are used for this purpose and the calibration results obtained during a radiosonde campaign in summer and autumn 2011 are presented. The water vapour profiles measured during night-time by the Raman lidar and radiosondes are compared and the differences between the methodologies are discussed. Then, a new approach to obtain relative humidity profiles by combination of simultaneous profiles of temperature (retrieved from a microwave radiometer) and water vapour mixing ratio (from a Raman lidar) is addressed. In the last part of this work, a statistical analysis of water vapour mixing ratio and relative humidity profiles obtained during 1 year of simultaneous measurements is presented. © Author(s) 2014. CC Attribution 3.0 License.

Corredor-Ardoy J.L.,University of Granada | Corredor-Ardoy J.L.,Andalusian Institute for Earth System Research IISTA | Bravo-Aranda J.A.,University of Granada | Bravo-Aranda J.A.,Andalusian Institute for Earth System Research IISTA | And 10 more authors.
Optica Pura y Aplicada | Year: 2014

The planetary boundary layer (PBL) is the lowest part of the atmosphere directly influenced by its contact with the land surface and it usually responds to changes in surface forcing in a time scale of an hour or less. Continuous monitoring of its height is highly important for atmospheric and environmental sciences. This work presents continuous monitoring of the PBL height (PBLH) using active (lidar and ceilometer) and passive (microwave radiometer, MWR) remote sensing instruments. Both methodologies are suitable for continuous monitoring of the planetary boundary layer under almost all weather conditions during daytime but, at nighttime ceilometer- and lidar-based techniques are limited due to the overlap of the instruments and MWR-based techniques are not always applicable due to lack of convection. The wavelet covariance transform method is applied to lidar and ceilometer data, optimizing in each case the detection of the PBL during daytime. Independent estimates using the parcel method with temperature profiles from a co-located passive MWR are used for comparison. Validation of both active and passive remote sensing techniques is performed at times when radiosoundings are available. © Sociedad Española de Óptica.

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