Suchergebnisse

This 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.2017.12.012 ; Knowledge 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).

"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-2409 ; Spanish Ministry of Economy and Competitiveness. Grant Numbers: CGL2016-81092-R, CGL2013-45410-R, CGL2014-52838-C2-1-R ; European Union's Horizon 2020 Research And Innovation Programme. Grant Number: 654109

In this work we adapt an empirical model to estimate ultraviolet erythemal irradiance (UVER) using experimental measurements carried out at seven stations in Spain during four years (2000–2003). The measurements were taken in the framework of the Spanish UVB radiometric network operated and maintained by the Spanish Meteorological Institute. The UVER observations are recorded as half hour average values. The model is valid for all-sky conditions, estimating UVER from the ozone columnar content and parameters usually registered in radiometric networks, such as global broadband hemispherical transmittance and optical air mass. One data set was used to develop the model and another independent set was used to validate it. The model provides satisfactory results, with low mean bias error (MBE) for all stations. In fact, MBEs are less than 4% and root mean square errors (RMSE) are below 18% (except for one location). The model has also been evaluated to estimate the UV index. The percentage of cases with differences of 0 UVI units is in the range of 61.1% to 72.0%, while the percentage of cases with differences of ±1 UVI unit covers the range of 95.6% to 99.2%. This result confirms the applicability of the model to estimate UVER irradiance and the UV index at those locations in the Iberian Peninsula where there are no UV radiation measurements. ; This work was supported by CICYT from the Spanish Ministry of Science and Technology through projects CIRRUS REN2003-03175 and PANDORA-CALIPSO CGL2004- 05984-C07-03, REN 2003- 03175 and Andalusian Regional Government project P06-RNM-01503. The "Instituto Nacional de Meteorología" kindly provided the radiometric and meteorological information for the stations used in this study.

This investigation focuses on the characterisation of the aerosol particle hygroscopicity. Aerosol particle optical properties were measured at Granada, Spain, during winter and spring seasons in 2013. Measured optical properties included particle light-absorption coefficient (sap) and particle light-scattering coefficient (ssp) at dry conditions and at relative humidity (RH) of 85 +/- 10%. The scattering enhancement factor, f(RH=85%), had a mean value of 1.5 +/- 0.2 and 1.6 +/- 0.3 for winter and spring campaigns, respectively. Cases of high scattering enhancement were more frequent during the spring campaign with 27% of the f(RH=85%) values above 1.8, while during the winter campaign only 8% of the data were above 1.8. A Saharan dust event (SDE), which occurred during the spring campaign, was characterised by a predominance of large particles with low hygroscopicity. For the day when the SDE was more intense, a mean daily value of f(RH=85%)=1.3 +/- 0.2 was calculated. f(RH=85%) diurnal cycle showed two minima during the morning and afternoon traffic rush hours due to the increase in non-hygroscopic particles such as black carbon and road dust. This was confirmed by small values of the single-scattering albedo and the scattering Angstrom exponent. A significant correlation between f(RH=85%) and the fraction of particulate organic matter and sulphate was obtained. Finally, the impact of ambient RH in the aerosol radiative forcing was found to be very small due to the low ambient RH. For high RH values, the hygroscopic effect should be taken into account since the aerosol forcing efficiency changed from -13W/m2 at dry conditions to -17W/m2 at RH=85%. ; This work was supported by the Andalusia Regional Government through projects P10-RNM-6299 and P12-RNM-2409; by the Spanish Ministry of Economy and Competitiveness through projects CGL2010-18782, CSD2007-00067, CGL2011-13580-E/CLI and CGL2011-16124-E; and by EU through ACTRIS project (EU INFRA-2010-1.1.16-262254). ; G. Titos was funded by the program FPI of the Spanish Ministry of Economy and Competitiveness – Secretariat of Science, Innovation and Development under grant BES-2011-043721.

This study analyses the aerosol optical and microphysical properties obtained by the Aerosol Robotic Network (AERONET) in seven different sites operating in the Iberian Peninsula during three coincident years (2010−2012) with the objective of studying different aerosol typing approaches. This area is of interest due to its location between the Sahara desert (the largest source of natural aerosols in the world) and mainland Europe (a relevant source of anthropogenic aerosols). In particular, we study the aerosol optical depth (AOD), Angström parameter (α440–870) and fine mode fraction (FMF), which are estimated from direct sun irradiance measurements. Additionally, the single scattering albedo (ωo) and aerosol particle size distribution (PSD), which are computed using additional sky radiances measurements under cloudless skies, are used in our analyses. The analyses show aerosol seasonal patterns in the AOD with maximum values in summer/spring and minimum values in winter/autumn for all the analysed stations. For α440–870, there are differences from site to site, with maximum values in winter and minimum values in summer for the southern locations, while there is not a remarkable pattern for the eastern locations close to the Mediterranean coast. The frequent and intense Saharan dust outbreaks over the southern Iberian Peninsula and the intense anthropogenic activity in the eastern urban locations are behind these seasonal patterns in the AOD and α440–870. In this work, two of the most employed classification schemes of aerosol type in the literature are used: one is based on the AOD and α440–870, the other one is based on ωo at 440 nm and the FMF and a new classification scheme based on ωo at 440 nm and FMF is proposed. The results revealed that the new classification method is more appropriate for distinguishing the aerosol types that affect the Iberian Peninsula. The relationship derived here between Δωo = ωo (440)- ωo (1020) and the FMF is demonstrated to be useful for aerosol type classification when no measurements of the sky radiances, and consequently of ωo(440), are available. Alternatively, the relationship between the ratio Δωo/ωo(440) and the FMF can be used because (Δωo/ωo) provides information about both the spectral ωo and the absolute values. ; Spanish Ministry of Economy and Competitiveness through projects CGL2013-45410-R ; Spanish Ministry of Economy and Competitiveness through projects CGL2016-81092-R ; Spanish Ministry of Economy and Competitiveness through projects CGL2017-90884-REDT ; Andalusia Regional Government through projects P12-RNM-2409

The presence of very high pollen levels in the atmosphere is associated with a strong impact on health and a worsening of symptoms in people who already have a respiratory disease. However, there is no specification on the aerobiological, environmental and meteorological factors that allow for characterizing a pollen event as of great magnitude due to the significant impact it can cause on the population and the environment. This work proposes criteria to typify the levels of atmospheric pollen as an extreme pollen event (EPE), and aims to determine the meteorological variables that can affect the presence and permanence of high pollen concentrations over a period of time. To address this goal, the quasi-climatological pollen dataset recorded in Granada (Southeastern Spain) during the period 1992-2019, has been used. On the daily accumulated pollen concentrations, the 95th, 97th and 99th percentiles were calculated. Spearman's correlation between the pollen concentration exceeding the proposed thresholds (C>P95, C>P97, C>P99) and surface meteorological variables recorded during up to five days before the event were established in order to identify the meteorological conditions that might affect the EPEs. As for the number of days with values higher than the established percentiles, it has been seen that in the case of total pollen and Olea, Cupressaceae and Pinus, there is a robust monotonically ascending trend throughout the study period. Regarding meteorological variables, relative humidity and 24-h accumulated precipitation are shown as the two most influential variables up to three days before the event, although temperatures, visibility and wind direction also show a correlation with some pollen types. The criteria proposed in this work allow us for classifying high levels of pollen as an EPE, and lay the foundations of these extreme events in a context of climate change in which they will become more frequent. ; the Spanish Ministry of Economy and Competitiveness (MINECO) for support through project BIOCLOUD (RTI2018-101154-A-100) and INTEGRATYON3 (PID2020.117825GB.C21) ; Regional Government of Andalusia through project AEROPRE (P18-RT-3820) and ADAPNE (P20-00136) ; INPARK (B-RNM-474-UGR18) ; DEM3TRIOS (A-RNM-430-UGR20) ; Earth System Excellence Units Program

This work focuses on the analysis of the seasonal cycle of temperature and relative humidity (RH) profiles and integrated water vapor (IWV) obtained from microwave radiometer (MWR) measurements over the mid-latitude city of Granada, southern Spain. For completeness the study, the maximum atmospheric boundary layer height (ABLHmax) is also included. To this end, we have firstly characterized the HATPRO-RPG MWR errors using 55 co-located radiosondes (RS) by means of the mean-bias (biasbar) profile and the standard deviation (SDbias) profile classified under all-weather conditions and cloud-free conditions. This characterization pointed out that temperature from HATPRO-MWR presents a very low biasbar respects RS mostly below 2.0 km agl, ranging from positive to negative values under all-weather conditions (from 1.7 to -0.4 K with SDbias up to 3.0 K). Under cloud-free conditions, the bias was very similar to that found under all-weather conditions (1.8 to -0.4 K) but with smaller SDbias (up to 1.1 K). The same behavior is also seen in this lower part (ground to 2.0 km agl) for RH. Under all-weather conditions, the mean RH bias ranged from 3.0 to -4.0% with SDbias between 10 and 16.3% while under cloud-free conditions the bias ranged from 2.0 to -0.4% with SDbias from 0.5 to 13.3%. Above 2.0 km agl, the SDbias error increases considerably up to 4 km agl (up to -20%), and then decreases slightly above 7.0 km agl (up to -5%). In addition, IWV values from MWR were also compared with the values obtained from the integration of RS profiles, showing a better linear fit under cloud-free conditions (R2 = 0.96) than under all-weather conditions (R2 = 0.82). The mean bias under cloud-free conditions was -0.80 kg/m2 while for all-weather conditions it was -1.25 kg/m2. Thus, the SDbiasfor all the statistics (temperature, RH and IWV) of the comparison between MWR and RS presented higher values for all-weather conditions than for cloud-free conditions ones. It points out that the presence of clouds is a key factor to take into account when MWR products are used. The second part of this work is devoted to a seasonal variability analysis over five years, leading us to characterize thermodynamically the troposphere over our site. This city atmosphere presents a clear seasonal cycle where temperature, ABLHmax and IWV increase from winter to summer and decrease in autumn, meanwhile RH decreases along the warmer seasons. This city presents cold winters (mean daily maximum temperature: 10.6 ± 1.1 °C) and dry/hot summers (mean daily maximum temperature of 28.8 ± 0.9 °C and mean daily maximum of surface RH up to 55.0 ± 6.0%) at surface (680 m asl). Moreover, considering temporal trends, our study pointed out that only temperature and RH showed a linear increase in winters with a mean-rate of (0.5 ± 0.1) °C/year and (3.4 ± 1.7) %/year, respectively, from ground to 2.0 km agl, meanwhile IWV presented a linear increase of 1.0 kg·m-2/year in winters, 0.78 kg·m-2/year in summers and a linear decrease in autumns of -0.75 kg·m-2/year. ; Andalusia Regional Government through project P12-RNM-2409 ; Spanish Ministry of Economy and Competitiveness through projects CGL2013-45410-R, CGL2015-73250-JIN and CGL2016-81092-R ; Juan de la Cierva grant IJCI-2016-30007

The AEAOD– ΔAEAOD grid proposed by Gobbi et al. (2007) is a graphical method used to visually represent the spectral characterization of aerosol optical depth (AOD), i.e. Angström exponent (AE) and its curvature, in order to infer the fine mode contribution (η) to the total AOD and the size of the fine mode aerosol particles. Perrone et al. (2014) applied this method for the wavelengths widely used in lidar measurements. However, in neither case does the method allow for a direct relationship between η and the fine mode fraction contribution to the total aerosol population. Some discussions are made regarding the effect of shape and composition to the classical AE-ΔAE plot. The potential use of particle backscatter measurements, widely used in aerosol characterization methods together with extinction measurements, is also discussed in the AE-ΔAE grid context. A modification is proposed that yields the submicron contribution to the total volume concentration by using particle extinction data, and a comparison to experimental measurements is made. Our results indicate that the use of a modified AE-ΔAE grid plot to directly obtain submicrometric and micrometric mode fraction to the total aerosol population is feasible if a volume-based bimodal particle size distribution is used instead of a number-based one. ; Andalusia Regional Government through project P12-RNM-2409 ; Spanish Ministry of Sciences, Innovation and Universities (CGL2016-81092 and CGL2017 -90884 - REDT)