Evaluation of the new ESR network software for the retrieval of direct sun products from CIMEL CE318 and PREDE POM01 sun-sky radiometers

The European Skynet Radiometers network (EuroSkyRad or ESR) has been recently established as a research network of European PREDE sun-sky radiometers. Moreover, ESR is federated with SKYNET, an international network of PREDE sun-sky radiometers mostly present in East Asia. In contrast to SKYNET, the European network also integrates users of the CIMEL CE318 sky–sun photometer. Keeping instrumental duality in mind, a set of open source algorithms has been developed consisting of two modules for (1) the retrieval of direct sun products (aerosol optical depth, wavelength exponent and water vapor) from the sun extinction measurements; and (2) the inversion of the sky radiance to derive other aerosol optical properties such as size distribution, single scattering albedo or refractive index. In this study we evaluate the ESR direct sun products in comparison with the AERosol RObotic NETwork (AERONET) products. Specifically, we have applied the ESR algorithm to a CIMEL CE318 and PREDE POM simultaneously for a 4-yr database measured at the Burjassot site (Valencia, Spain), and compared the resultant products with the AERONET direct sun measurements obtained with the same CIMEL CE318 sky–sun photometer. The comparison shows that aerosol optical depth differences are mostly within the nominal uncertainty of 0.003 for a standard calibration instrument, and fall within the nominal AERONET uncertainty of 0.01–0.02 for a field instrument in the spectral range 340 to 1020 nm. In the cases of the Ångström exponent and the columnar water vapor, the differences are lower than 0.02 and 0.15 cm, respectively. Therefore, we present an open source code program that can be used with both CIMEL and PREDE sky radiometers and whose results are equivalent to AERONET and SKYNET retrievals

Column aerosol characterization in a semi‐arid region around Marrakech during the WATERMED 2003 campaign

In the framework of the WATERMED (WATer use efficiency in natural vegetation and agricultural areas by Remote sensing in the MEDiterranean basin) project, an experimental field campaign was carried out in a semi‐arid region near Marrakech, Morocco, during March 2003. This work focused on the columnar aerosol characterization from spectroradiometric and photometric measurements of direct solar irradiance and sky radiance at ground level. The results show a high dependence of the aerosol optical properties on the air masses present in the area. Two periods with different aerosol loads were observed in the campaign. In the first, Atlantic‐origin aerosols showed a marine particle accumulation mode combined with a dominant mode corresponding to coarse particles of local origin. In the second period the synoptic situation changed towards a Saharan+Atlantic origin, the Atlantic influence persisting at altitude while at lower levels the presence of air masses proceeding from the Saharan desert was observed. This dry air carried a large quantity of mineral particles that increased the area's turbidity, leading to a substantial increase in the volume of the whole distribution, a displacement of the accumulation mode radius towards higher values and an increasingly evident spread of the coarse particle mode, although the radius remained the same as that in the first period of the campaign

Retrieval of characteristic parameters for water vapour transmittance in the development of ground based Sun-Sky radiometric measurements of columnar water vapour

Sunsky radiometers are instruments created for aerosol study, but they can measure in the water vapour absorption band allowing the estimation of columnar water vapour in clear sky simultaneously with aerosol characteristics, with high temporal resolution. A new methodology is presented for estimating calibration parameters (i.e. characteristic parameters of the atmospheric transmittance and solar calibration constant) directly from the sunsky radiometer measurements. The methodology is based on the hypothesis that characteristic parameters of the atmospheric transmittance are dependent on vertical profiles of pressure, temperature and moisture occurring at each site of measurement. To obtain the parameters from the proposed methodology some seasonal independent measurements of columnar water vapour taken over a large range of solar zenith angle simultaneously with the sunsky radiometer measurements, are needed. In this work high time resolution columnar water vapour measurements by GPS were used as independent data set, but also the case when such measurements are not available was considered by developing the surface humidity method (SHM). This methodology makes it possible to retrieve the needed independent data set of columnar water vapour using the standard surface meteorological observations (temperature, pressure and relative humidity) more readily available. The time pattern of columnar water vapour from sunsky radiometer retrieved using both the methodologies was compared with simultaneous measurements from microwave radiometer, radiosondings and GPS. Water vapour from sunsky radiometer, obtained using GPS independent measurements, was characterized by an error varying from 1% up to 5%, whereas water vapour from SHM showed an error from 1% up to 11%, depending on the local columnar water occurring at the site during the year. These errors were estimated by comparing water vapour series from sunsky radiometer against measurements taken by GPS at a nearby station. The accordance between retrievals from sunsky radiometer and simultaneous measurements from the other instruments was found always within the error both in the case of SHM and of the GPS independent data set. Water vapour obtained using characteristic parameters of the atmospheric transmittance dependent on water vapour was also compared against GPS retrievals, showing a clear improvement with respect to the case when these parameters are kept fixed

Unexpected vertical structure of the Saharan Air Layer and giant dust particles during AER-D

The Saharan Air Layer (SAL) in the summertime eastern Atlantic is typically well mixed and 3-4 km deep, overlying the marine boundary layer (MBL). In this paper, we show experimental evidence that at times a very different structure can be observed. During the AERosol properties - Dust (AER-D) airborne campaign in August 2015, the typical structure described above was observed most of the time, and was associated with a moderate dust content yielding an aerosol optical depth (AOD) of 0.3-0.4 at 355 nm. In an intense event, however, an unprecedented vertical structure was observed close to the eastern boundary of the basin, displaying an uneven vertical distribution and a very large AOD (1.5-2), with most of the dust in a much lower level than usual (0.3-2 km). Estimated dust concentrations and column loadings for all flights during the campaign spanned 300-5500 and 0.8-7.5 g m−2, respectively. The shortwave direct radiative impact of the intense dust event has been evaluated to be as large as −260±30 and −120±15 W m−2 at the surface and top of atmosphere (TOA), respectively. We also report the correlation of this event with anomalous lightning activity in the Canary Islands. In all cases, our measurements detected a broad distribution of aerosol sizes, ranging from ∼0.1 to ∼80 µm (diameter), thus highlighting the presence of giant particles. Giant dust particles were also found in the MBL. We note that most aerosol models may miss the giant particles due to the fact that they use size bins up to 10-25 µm. The unusual vertical structure and the giant particles may have implications for dust transport over the Atlantic during intense events and may affect the estimate of dust deposited to the ocean. We believe that future campaigns could focus more on events with high aerosol load and that instrumentation capable of detecting giant particles will be key to dust observations in this part of the world

Determination and analysis of in situ spectral aerosol optical properties by a multi-instrumental approach

Continuous in situ measurements of aerosol optical properties were conducted from 29 June to 29 July 2012 in Granada (Spain) with a seven-wavelength Aethalometer, a Multi-Angle Absorption Photometer, and a three-wavelength integrating nephelometer. The aim of this work is to describe a methodology to obtain the absorption coefficients (babs) for the different Aethalometer wavelengths. In this way, data have been compensated using algorithms which best estimate the compensation factors needed. Two empirical factors are used to infer the absorption coefficients from the Aethalometer measurements: C – the parameter describing the enhancement of absorption by particles in the filter matrix due to multiple scattering of light in the filter matrix – and f, the parameter compensating for non-linear loading effects in the filter matrix. Spectral dependence of f found in this study is not very strong. Values for the campaign lie in the range from 1.15 at 370 nm to 1.11 at 950 nm. Wavelength dependence in C proves to be more important, and also more difficult to calculate. The values obtained span from 3.42 at 370 nm to 4.59 at 950 nm. Furthermore, the temporal evolution of the Ångström exponent of absorption (αabs) and the single-scattering albedo (ω0) is presented. On average αabs is around 1.1 ± 0.3, and ω0 is 0.78 ± 0.08 and 0.74 ± 0.09 at 370 and 950 nm, respectively. These are typical values for sites with a predominance of absorbing particles, and the urban measurement site in this study is such. The babs average values are of 16 ± 10 Mm−1 (at 370 nm) and 5 ± 3 Mm−1 (at 950 nm), respectively. Finally, differences between workdays and Sundays have been further analysed, obtaining higher babs and lower ω0 during the workdays than on Sundays as a consequence of the diesel traffic influence.This work was financed jointly by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund through projects CGL2011-24290, CGL2010-18782, CSD2007-00067, and CGL2012-33294; by the Valencia Autonomous Government through project PROMETEO/2010/064; the Andalusia Regional Government through projects P08-RNM-3568 and P10-RNM-6299; and by the Slovenian Ministry of Economic Development and Technology JR-KROP grant 3211-11-000519. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 262254 (ACTRIS). The collaboration of S. Segura in this work was possible thanks to fellowship BES-2010-031626

Estudio comparado del rendimiento de los alumnos de primer curso procedentes de C.O.U. frente a los alumnos procedentes de F.P.

De los 450 alumnos de nuevo ingreso que actualmente se matriculan en las titulaciones de Ingeniería Técnica de Informática de Gestión (ITIG) o de Sistemas (ITIS,) en la Escuela Universitaria de Informática de la Universidad Politécnica de Valencia, 135 proceden de Formación Profesional (FP), mientras que la mayor parte del resto han cursado previamente el Curso de Orientación Universitaria (COU). Esta distinta procedencia provoca una importante heterogeneidad en el alumnado, pues mientras se constata, por ejemplo, una mayor habilidad de los alumnos procedentes de F.P. en algunas prácticas de laboratorio, también se evidencian en estos últimos, unas mayores carencias en lo que a conocimientos básicos se refiere, especialmente en Matemáticas. En este trabajo se compara el rendimiento académico de los alumnos de nuevo ingreso procedentes de COU frente al de los procedentes de FP, durante los cuatro cursos de vigencia del actual plan de estudios. Dado que los datos del estudio reflejan unos índices de fracaso académico muy superiores en los alumnos procedentes de FP que en los de COU, desde el curso 96-97, la Escuela decidió implantar en el primer cuatrimestre, una asignatura optativa, Elementos de Matemáticas, recomendada para los alumnos procedentes de F.P., con el fin de mitigar esa falta de conocimientos básicos. Los resultados del primer curso de implantación reflejan una cierta mejora sobre los cursos anteriores

Intercomparison of spectroradiometers and Sun photometers for the determination of the aerosol optical depth during the VELETA-2002 field campaign

[ 1] In July 2002 the VELETA-2002 field campaign was held in Sierra Nevada ( Granada) in the south of Spain. The main objectives of this field campaign were the study of the influence of elevation and atmospheric aerosols on measured UV radiation. In the first stage of the field campaign, a common calibration and intercomparison between Licor-1800 spectroradiometers and Cimel-318 Sun photometers was performed in order to assess the quality of the measurements from the whole campaign. The intercomparison of the Licor spectroradiometers showed, for both direct and global irradiances, that when the comparisons were restricted to the visible part of the spectrum the deviations were within the instruments' nominal accuracies which allows us to rely on these instruments for measuring physical properties of aerosols at the different measurement stations. A simultaneous calibration on AOD data was performed for the Cimel-318 Sun photometers. When a common calibration and methodology was applied, the deviation was lowered to much less than 0.01 for AOD. At the same time an intercomparison has been made between the AOD values given by the spectroradiometers and the Sun photometers, with deviations obtained from 0.01 to 0.03 for the AOD in the visible range, depending on the channel. In the UVA range, the AOD uncertainty was estimated to be around 0.02 and 0.05 for Cimel and Licor respectively. In general the experimental differences were in agreement with this uncertainty estimation. In the UVB range the AOD measurements should not be used due to maximum instrumental uncertainties

Precipitable water vapour content from ESR/SKYNET sun-sky radiometers: validation against GNSS/GPS and AERONET over three different sites in Europe

The estimation of the precipitable water vapour content (W) with high temporal and spatial resolution is of great interest to both meteorological and climatological studies. Several methodologies based on remote sensing techniques have been recently developed in order to obtain accurate and frequent measurements of this atmospheric parameter. Among them, the relative low cost and easy deployment of sun-sky radiometers, or sun photometers, operating in several international networks, allowed the development of automatic estimations of W from these instruments with high temporal resolution. However, the great problem of this methodology is the estimation of the sun-photometric calibration parameters. The objective of this paper is to validate a new methodology based on the hypothesis that the calibration parameters characterizing the atmospheric transmittance at 940nm are dependent on vertical profiles of temperature, air pressure and moisture typical of each measurement site. To obtain the calibration parameters some simultaneously seasonal measurements of W, from independent sources, taken over a large range of solar zenith angle and covering a wide range of W, are needed. In this work yearly GNSS/GPS datasets were used for obtaining a table of photometric calibration constants and the methodology was applied and validated in three European ESR-SKYNET network sites, characterized by different atmospheric and climatic conditions: Rome, Valencia and Aosta. Results were validated against the GNSS/GPS and AErosol RObotic NETwork (AERONET) W estimations. In both the validations the agreement was very high, with a percentage RMSD of about 6, 13 and 8% in the case of GPS intercomparison at Rome, Aosta and Valencia, respectively, and of 8% in the case of AERONET comparison in Valencia. Analysing the results by W classes, the present methodology was found to clearly improve W estimation at low W content when compared against AERONET in terms of %bias, bringing the agreement with the GPS (considered the reference one) from a %bias of 5.76 to 0.52

Evolution of chemical composition and gas emissions from aged pig slurry during outdoor storage with and without prior solid separation

Chemical composition and gas emissions from two types of pig slurry were evaluated: the liquid fraction of mechanical solid-liquid separated slurry (SS), and raw slurry (RS). The slurry was obtained at the end of a pig fattening period and was stored in 100 l vessels for 15 weeks simulating outdoor storage conditions. During this period, representative samples were taken and analysed for chemical composition. Methane, carbon dioxide, ammonia, water vapour and nitrous oxide emissions were recorded. The results showed a high biological degradation during the first five weeks of outdoor storage in SS and RS slurries, as a result of an increase in the dissolved chemical oxygen demand, volatile fatty acids and carbon dioxide emission observed in this period. However, methanogenic activity was not evident until week 6 of storage in both slurries, confirmed by the volatile fatty acids accumulation and the negligible methane emissions during the first five weeks of storage. The results showed that differences in the initial slurry organic matter content, influenced by solid separation process affects the evolution pattern of the organic matter degradation. Storage time can considerably affect the biodegradability of organic matter in pig slurry. © 2011 IAgrE.This work was supported by the Agrobiogas project financed by the Agroalimed Foundation of the Conselleria de Agricultura, Pesca, Alimentacion y Agua of Valencia, Spain.Moset, V.; Cambra López, M.; Estellés, F.; Torres Salvador, AG.; Cerisuelo, A. (2012). Evolution of chemical composition and gas emissions from aged pig slurry during outdoor storage with and without prior solid separation. Biosystems Engineering. 111(1):2-10. doi:10.1016/j.biosystemseng.2011.10.001S210111

Estudio de la influencia sobre el rendimiento académico de la nota de acceso y procedencia (COU/FP) en la E.U. de Informática

Se ha desarrollado una herramienta informática que permite realizar estudios de rendimiento académico. En este trabajo se muestran los resultados, a lo largo del tiempo, de los alumnos de nuevo ingreso en la EUI teniendo en cuenta su procedencia y su nota de acceso. Se ha hecho un estudio estadístico ponderado que muestra la influencia de los factores apuntados, relacionándolos con otros anteriormente observados