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Dive into the research topics where J. M. Vilaplana is active.

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Featured researches published by J. M. Vilaplana.


Atmospheric Chemistry and Physics | 2010

Comparison of UV irradiances from Aura/Ozone Monitoring Instrument (OMI) with Brewer measurements at El Arenosillo (Spain) – Part 2: Analysis of site aerosol influence

M. Antón; Victoria E. Cachorro; J. M. Vilaplana; C. Toledano; N. Krotkov; Antti Arola; A. Serrano; B. A. de la Morena

Several validation studies have shown a notable overestimation of the clear sky ultraviolet (UV) irradiance at the Earth’s surface derived from satellite sensors such as the Total Ozone Mapping Spectrometer (TOMS) and the Ozone Monitoring Instrument (OMI) with respect to groundbased UV data at many locations. Most of this positive bias is attributed to boundary layer aerosol absorption that is not accounted for in the TOMS/OMI operational UV algorithm. Therefore, the main objective of this study is to analyse the aerosol effect on the bias between OMI erythemal UV irradiance (UVER) and spectral UV (305 nm, 310 nm and 324 nm) surface irradiances and ground-based Brewer spectroradiometer measurements from October 2004 to December 2008 at El Arenosillo station (37.1 ◦ N, 6.7 W, 20 m a.s.l.), with meteorological conditions representative of the South-West of Spain. The effects of other factors as clouds, ozone and the solar elevation over this intercomparison were analysed in detail in a companion paper (Ant ón et al., 2010). In that paper the aerosol effects were studied making only a rough evaluation based on aerosol optical depth (AOD) information at 440 nm wavelength (visible range) without applying any correction. We have used the precise information given by single scattering albedo (SSA) from AERONET for the determination of Correspondence to: V. E. Cachorro ([email protected]) absorbing aerosols which has allowed the correction of the OMI UV data. An aerosol correction expression was applied to the OMI operational UV data using two approaches to estimate the UV absorption aerosol optical depth, AAOD. The first approach was based on an assumption of constant SSA value of 0.91. This approach reduces the OMI UVER bias against the reference Brewer data from 13.4% to 8.4%. Second approach uses daily AERONET SSA values reducing the bias only to 11.6%. Therefore we have obtained a 37% and 12% of improvement respectively. For the spectral irradiance at 324 nm, the OMI bias is reduced from 10.5% to 6.98% for constant SSA and to 9.03% for variable SSA. Similar results were obtained for spectral irradiances at 305 nm, and 310 nm. Contrary to what was expected, the constant SSA approach has a greater bias reduction than variable SSA, but this is a reasonable result according to the discussion about the reliability of SSA values. Our results reflect the level of accuracy that may be reached at the present time in this type of comparison, which may be considered as satisfactory taking into account the remaining dependence on other factors. Nevertheless, improvements must be accomplished to determine reliable absorbing aerosol properties, which appear as a limiting factor for improving OMI retrievals. Published by Copernicus Publications on behalf of the European Geosciences Union. 11868 V. E. Cachorro et al.: Part 2: Analysis of site aerosol influence


Photochemistry and Photobiology | 2005

An Improved Outdoor Calibration Procedure for Broadband Ultraviolet Radiometers

M. L. Cancillo; A. Serrano; M. Antón; José Agustín García; J. M. Vilaplana; B. A. de la Morena

This article aims at improving the broadband ultraviolet radiometers calibration methodology. For this goal, three broadband radiometers are calibrated against a spectrophotometer of reference. Three different one‐step calibration models are tested: ratio, first order and second order. The latter is proposed in order to adequately reproduce the high dependence on the solar zenith angle shown by the other two models and, therefore, to improve the calibration performance at high solar elevations. The proposed new second‐order model requires no additional information and, thus, keeps the operational character of the one‐step methodology. The models are compared in terms of their root mean square error and the most qualified is subsequently validated by comparing its predictions with the spectrophotometer measurements within an independent validation data subset. Results show that the best calibration is achieved by the second‐order model, with a mean bias error and mean absolute bias error lower than 2.2 and 6.7%, respectively.


Science of The Total Environment | 2015

A long-term study of new particle formation in a coastal environment: Meteorology, gas phase and solar radiation implications

M. Sorribas; J.A. Adame; F.J. Olmo; J. M. Vilaplana; Manuel Gil-Ojeda; L. Alados-Arboledas

New particle formation (NPF) was investigated at a coastal background site in Southwest Spain over a four-year period using a Scanning Particle Mobility Sizer (SMPS). The goals of the study were to characterise the NPF and to investigate their relationship to meteorology, gas phase (O3, SO2, CO and NO2) and solar radiation (UVA, UVB and global). A methodology for identifying and classifying the NPF was implemented using the wind direction and modal concentrations as inputs. NPF events showed a frequency of 24% of the total days analysed. The mean duration was 9.2±4.2 h. Contrary to previous studies conducted in other locations, the NPF frequency reached its maximum during cold seasons for approximately 30% of the days. The lowest frequency took place in July with 10%, and the seasonal wind pattern was found to be the most important parameter influencing the NPF frequency. The mean formation rate was 2.2±1.7 cm(-3) s(-1), with a maximum in the spring and early autumn and a minimum during the summer and winter. The mean growth rate was 3.8±2.4 nm h(-1) with higher values occurring from spring to autumn. The mean and seasonal formation and growth rates are in agreement with previous observations from continental sites in the Northern Hemisphere. NPF classification of different classes was conducted to explore the effect of synoptic and regional-scale patterns on NPF and growth. The results show that under a breeze regime, the temperature indirectly affects NPF events. Higher temperatures increase the strength of the breeze recirculation, favouring gas accumulation and subsequent NPF appearance. Additionally, the role of high relative humidity in inhibiting the NPF was evinced during synoptic scenarios. The remaining meteorological variables (RH), trace gases (CO and NO), solar radiation, PM10 and condensation sink, showed a moderate or high connection with both formation and growth rates.


IEEE Transactions on Geoscience and Remote Sensing | 2010

The Empirically Corrected EP-TOMS Total Ozone Data Against Brewer Measurements at El Arenosillo (Southwestern Spain)

M. Antón; J. M. Vilaplana; M. Kroon; A. Serrano; Marta Parias; M. L. Cancillo; Benito de la Morena

This paper focuses on the validation of the empirically corrected total ozone column (TOC) data provided by the Earth Probe Total Ozone Mapping Spectrometer (EP-TOMS) using ground-based measurements recorded by a well-calibrated Brewer spectroradiometer located at El Arenosillo (Spain). In addition, satellite TOC observations derived from the Ozone Monitoring Instrument (OMI) with the TOMS algorithm are also used in this paper. The agreement between EP-TOMS TOC data and Brewer measurements is excellent (R2 ~ 0.92) even for the period 2000-2005 when a higher EP-TOMS instrument degradation occurred. Despite its low magnitude, the EP-TOMS-Brewer relative differences depend on the solar zenith angle (SZA), showing a clear seasonal cycle with amplitude between ±2% and ±4%. Conversely, OMI-Brewer relative differences show a constant negative value around -1% with no significant dependence on SZA. No significant dependence on the ground-based to satellite-based differences with respect to the EP-TOMS scene or to the OMI crosstrack position is observed for either satellite retrieval algorithm. Finally, TOC, estimated by the two satellite instruments, have also been compared, showing a good agreement (R2 ~ 0.88). Overall, we conclude that the empirical correction of the EP-TOMS data record provides a reprocessed set of high quality. However, EP-TOMS data after year 2000 should not be used in calculations of global-ozone trending due to remaining errors in the data set and because it is no longer an independent data set.


Journal of Atmospheric and Oceanic Technology | 2008

Correction of Angular Response Error in Brewer UV Irradiance Measurements

M. Antón; A Ntonio Serrano; M. L. Cancillo; J. M. Vilaplana; Victoria E. Cachorro; Julian Gröbner

Abstract Ultraviolet spectral irradiance measured by spectroradiometers usually presents high deviations from the ideal angular response due to imperfections in the entrance optics. In this paper a methodology to correct the angular error in the global UV spectral measurements of a Brewer MKIII spectroradiometer under all weather conditions is presented. This methodology calculates the global correction factor as a function of three variables: the direct irradiance correction factor, the diffuse irradiance correction factor, and a factor depending on the direct-to-global irradiance ratio. This work contributes to better measuring the UV radiation by improving the parameterization of the clouds effects. Depending mainly on wavelength, solar zenith angle, and cloud optical thickness, the angular correction obtained ranges from 2% to 9%. The accuracy of this correction is limited by the uncertainties in the measured angular response and in the ratio of direct to global radiation. The original and the correct...


Journal of Geophysical Research | 2016

Global irradiance calibration of multifilter UV radiometers

A. A. Piedehierro; M. L. Cancillo; A. Serrano; M. Antón; J. M. Vilaplana

It is well known that the amount of ultraviolet solar radiation (UV) reaching the Earths surface is governed by stratospheric ozone, which has exhibited notable variations since the late 1970s. A thorough monitoring of UV radiation requires long-term series of accurate measurements worldwide, and to keep track of its evolution, it is essential to use high-quality instrumentation with an excellent long-term performance capable of detecting low UV signal. There are several UV monitoring networks worldwide based on multifilter UV radiometers; however, there is no general agreement about the most suitable methodology for the global irradiance calibration of these instruments. This paper aims to compare several calibration methods and to analyze their behavior for different ranges of solar zenith angle (SZA). Four methods are studied: the two currently most frequently used methods referred to in the literature and two new methods that reduce systematic errors in calibrated data at large solar zenith angles. The results evidence that proposed new methods show a clear improvement compared to the classic approaches at high SZA, especially for channels 305 and 320 nm. These two channels are of great interest for calculating the total ozone column and other products such as dose rates of biological interest in the UV range (e.g., the erythemal dose).


Atmospheric Chemistry and Physics | 2007

Improving the solar zenith angle dependence of broadband UV radiometers calibration

M. L. Cancillo; A. Serrano; M. Antón; J. A. García; J. M. Vilaplana

This paper focusses on the proposal of a new method for the calibration of broadband ultraviolet radiometers. The advantage of the method proposed is the accurate modelling of the dependence on the solar zenith angle. The new model is compared with other one-step calibration methods and with the two-step method, which requires the knowledge of the actual response of the broadband radiometer. For this purpose, three broadband radiometers are calibrated against a spectrophotometer of reference. The new method is validated comparing its predictions with the spectrophotometer measurements using an independent data set.


Recent Advances in Multidisciplinary Applied Physics#R##N#Proceedings of the First International Meeting on Applied Physics (APHYS-2003) October 13-18th 2003, Badajoz, Spain | 2005

The PHOTONS - AERONET Network Stations in Spain

Victoria E. Cachorro; C. Toledano; Ricardo Vergaz; A. M. de Frutos; M. Sorribas; J. M. Vilaplana; B. A. de la Morena

Abstract The Atmospheric Optics Group of the University of Valladolid, Spain (GOA-UVA) in collaboration with the Instituto Nacional de Tecnica Aeroespacial (INTA) has been measuring direct solar irradiance and sky radiance with a Cimel sun-photometer belonging to PHOTONS-AERONET since February 2000 up to date. The site for measurements “El Arenosillo” is located in the southwest coast of Spain (37.1° N, 6.7° W). Since January 2003 another Cimel sunphotometer is operating in Palencia (41.9°N, 4.5°W), located in a continental area of north-central Spain. The characteristics and protocols for measurements, data transmission and processing of the sunphotometers according to AERONET standards are described. Problems due to calibration were detected and solved by development of a new correction method (KCICLO). The method provides in situ correction for Aerosol Optical Depth (AOD) measurements as well as it explains the AOD fictitious diurnal cycle detected in the data series.


Proceedings of SPIE | 2009

Ozone monitoring instrument satellite UV irradiance product correction using a global aerosol climatology

Antti Arola; S. Kazadzis; J. Kujanpää; Anders Lindfors; A. F. Bais; Ann R. Webb; Philipp Weihs; A. di Sarra; Tapani Koskela; M. Janousch; J. M. Vilaplana; A. M. Sianni; Colette Brogniez

Lately a number of studies related with UV irradiance estimates from satellite data based on the Ozone Monitoring Instrument (OMI) have shown a high correlation with ground-based measurements but a positive bias in many locations, the satellite derived UV being higher. One of the key factors that this bias has been attributed to is the boundary layer aerosol absorption not taken into account in the current OMI UV algorithm. In this work we have used a correction procedure based on climatological global aerosol absorption data taken from AeroComm aerosol initiative. This dataset includes aerosol optical depth and aerosol single scattering albedo assembled by combining, ground-based aerosol measurements from AERONET and information from several global aerosol models. The results of this correction were compared with synchronous ground-based measurements from 9 UV monitoring stations. The results generally showed a significantly reduced bias of 7-20%, a lower variability, and an unchanged, high correlation coefficient.


Advances in Space Research | 1997

Experimental investigation of the coupling process in the middle atmosphere/lower thermosphere/ionosphere system

B. A. de la Morena; R. Rodrigo; E.S. Kazimirovsky; J. M. Vilaplana

Abstract The paper briefly reviews some investigations realized mainly in Southern Spain of possible coupling between middle atmosphere, lower thermosphere and ionosphere. It draws attention to abnormal circulation changes in the winter stratosphere, detected through variations of D-region ionospheric radiowave absorption; the response of the lower ionosphere to the stratospheric warmings; quasi-periodic fluctuations in ionospheric absorption in relation to planetary wave activity in the stratosphere; the statistically significant correlations between variations of total ozone content considered as a parameter of the stratospheric changes; and radio waves absorption as an indicator of the electron density in the lower ionosphere. There is some difference in the behaviour of the lower ionosphere in relation to meteorological parameters in Southern Spain and Central and East Europe, and this is discussed as partly due to latitudinal variations of ionospheric parameters and to longitudinal inhomogeneity of lower atmosphere processes.

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M. Antón

University of Extremadura

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A. Serrano

University of Extremadura

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M. L. Cancillo

University of Extremadura

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M. Bañón

Agencia Estatal de Meteorología

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María M. López

Agencia Estatal de Meteorología

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Alberto Redondas

Agencia Estatal de Meteorología

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C. Toledano

University of Valladolid

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