A new empirical model to estimate hourly diffuse photosynthetic photon flux density

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.2017.12.012Knowledge 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)

Adaptation of an empirical model for erythemal ultraviolet irradiance

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

Effects of Environmental Stress on the Pollen Viability of Ornamental Tree-Species in the City of Granada (South-Eastern Spain)

Atmospheric conditions, as well as pollutants, can induce changes in the viability and germinability of the pollen grain. This process frequently occurs in cities due to the high rate of air pollution that can alter the quality of pollen, affecting its biological functions. In this work, the effect of different environmental stress factors, mainly UV-B radiation and polluting gases (CO, NO2 and SO2), on the viability and maturity of the pollen of four ornamental tree-species present in the green infrastructure of Granada, namely Acer negundo, Carpinus betulus, Olea europaea and Cupressus spp. is analyzed. Differential staining techniques were used with fresh pollen collected in areas with different exposure to environmental stress to detect intact cell membranes (Trypan blue) and the state of maturity (Pyrogallol red). It was observed that the species from sectors more exposed to environmental stress registered a low viability and were affected by factors such as UV-B radiation and atmospheric pollutants. On the contrary, the pollen from tree species growing in peri-urban forests presented a higher rate of viability and less effect of pollutant factors. Differences were also observed according to the species/genus and according to the sampling area. This modification in the morphological and/or organic composition of the pollen wall may cause a loss of quality in the reproductive processes of plants, and it may be bioindicator of the process of progressive degradation that plant species can experience in urban environments under conditions of environmental stress, and prevent the impacts that can affect other species

Improving the Estimation of the Diffuse Component of Photosynthetically Active Radiation (PAR)

Most weather forecasting models are not able to accurately reproduce the great variability existing in the measurements of the diffuse component of photosynthetically active radiation (PAR; 400–700 nm) under all sky conditions. Based on the well-known relationship between the diffuse fraction (k) and the clearness index (kt), this study addresses improvements in estimations by proposing adaptations of previous models, which were previously applied only to the total solar irradiance (TSI; 280–3,000 nm). In order to reproduce this variability, additional parameters were introduced. The models were tested employing a multisite database gathered at the Mediterranean basin. Since Artificial Neural Network (ANN) models are not limited to fixed coefficients to predict the diffuse fraction of PAR (kPAR), these types of models are more accurate than empirical ones, reaching determination coefficients (r2) up to 0.998. However, the simpler linear model proposed by Foyo-Moreno et al. (2018), https://doi.org/10.1016/j.atmosres.2017.12.012 shows a similar performance to the ANN models, directly predicting the diffuse component of PAR (PARDiffuse) from TSIDiffuse, with a r2 up to 0.997. Results obtained here also determine that the most important variables for estimating PARDiffuse are kt or kt,PAR, and the apparent solar time (AST). Therefore, PARDiffuse can be modeled using TSI measured in most radiometric stations, reaching r2 up to 0.858 for empirical models and 0.970 for ANN models. This modified approach will allow for the very accurate construction of long-term data series of PARDiffuse in regions where continuous measurements of PAR are not available.Spanish Ministry of Economy and Competitiveness (projects CGL2017-90884- REDT and PID2020-120015RB-I00)Andalusia Regional Government, University of Granada and FEDER funds (project B-RNM-524-UGR20)Open Access funding provided by University of Helsink

Aerosol radiative effects in photosynthetically active radiation and total irradiance at a Mediterranean site from an 11-year database

This study addresses the analysis of the aerosol radiative forcing (ARF) and aerosol forcing efficiency (AFE) at surface in the Photosynthetically Active and Total radiation ranges in a Southwest Mediterranean site. A thorough analysis of a long-term database (2008–2018) has been performed, bringing very valuable results about both, the absolute values and trends in ARF and AFE for both spectral intervals. The largest monthly mean for aerosol optical depth at 500 nm (AOD500) is found in summer (0.16 at July and August) meanwhile the lowest value is in winter (0.08 at November and December), with an interannual range varying from 0.11 ± 0.03 (in 2018) to 0.17 ± 0.03 (in 2014). The AFE variation range has been estimated between −12 and − 198 Wm−2τ−1 for PAR and between −9 and − 450 Wm−2τ−1 for Total irradiance. ARF varies between −1 Wm−2 and -23 Wm−2 in the PAR range, taking values from −1 to −40 Wm−2 in the Total one. This result points out the relevance of the aerosol effects on the PAR range, which can involve up to a 50% of the Total ARF. Moreover, a notable dependence of ARF and AFE on the solar position has been detected, increasing their absolute values at solar zenith angle from 0o to 45o-60o and decreasing to zero for lower solar positions. Additionally, this analysis has revealed the existence of a significant downward trend in AFE values for PAR, with a slope of 2.7 Wm−2τ−1year−1. Although the slope is positive, taking into account that the AFE values are negative, the slope value implies that the aerosol cooling radiative effect of aerosols is decreasing. However, no trends have been detected neither in AFE nor ARF values in the Total solar range. These results evidence the long-term aerosol effects over the different spectral intervals and emphasize the need for detailed analysis of the aerosol radiative effects on fundamental spectral intervals such as the PAR range.Peer reviewe

Study of the relative humidity dependence of aerosol light-scattering in southern Spain

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 (σap) and particle light-scattering coefficient (σsp) 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 Ångstrom 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 −13 W/m2 at dry conditions to −17 W/m2 at RH=85%

Contribution to column-integrated aerosol typing based on Sunphotometry using different criteria

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-RSpanish Ministry of Economy and Competitiveness through projects CGL2016-81092-RSpanish Ministry of Economy and Competitiveness through projects CGL2017-90884-REDTAndalusia Regional Government through projects P12-RNM-240

Assessing pollen extreme events over a Mediterranean site: Role of local surface meteorology

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 Progra

Characterization of Tajogaite volcanic plumes detected over the Iberian Peninsula from a set of satellite and ground-based remote sensing instrumentation

Three volcanic plumes were detected during the Tajogaite volcano eruptive activity (Canary Islands, Spain, September–December 2021) over the Iberian Peninsula. The spatiotemporal evolution of these events is characterised by combining passive satellite remote sensing and ground-based lidar and sun-photometer systems. The inversion algorithm GRASP is used with a suite of ground-based remote sensing instruments such as lidar/ceilometer and sun-photometer from eight sites at different locations throughout the Iberian Peninsula. Satellite observations showed that the volcanic ash plumes remained nearby the Canary Islands covering a mean area of 120 ± 202 km2 during the whole period of eruptive activity and that sulphur dioxide plumes reached the Iberian Peninsula. Remote sensing observations showed that the three events were mainly composed of sulphates, which were transported from the volcano into the free troposphere. The high backscatter-related Ångström exponents for wavelengths 532–1064 nm (1.17 ± 0.20 to 1.40 ± 0.24) and low particle depolarization ratios (0.08 ± 0.02 to 0.09 ± 0.02), measured by the multi-wavelength Raman lidar, hinted at the presence of spherical small particles. The layer aerosol optical depth at 532 nm (AODL532) obtained from lidar measurements contributed between 49% and 82% to the AERONET total column AOD at 532 nm in event II (11–13 October). According to the GRASP retrievals, the layer aerosol optical depth at 440 nm (AODL440) was higher in all sites during event II with values between 0.097 (Badajoz) and 0.233 (Guadiana-UGR) and lower in event III (19–21 October) varying between 0.003 (Granada) and 0.026 (Évora). Compared with the GRASP retrievals of total column AOD at 440 nm, the AODL440 had contributions between 21% and 52% during event II. In the event I (25–28 September), the mean volume concentrations (VC) varied between 5 ± 4 μm3cm−3 (El-Arenosillo/Huelva) and 17 ± 10 μm3cm−3 (Guadiana-UGR), while in event II this variation was from 11 ± 7 μm3cm−3 (Badajoz) to 27 ± 10 μm3cm−3 (Guadiana-UGR). Due to the impact of volcanic events on atmospheric and economic fields, such as radiative forcing and airspace security, a proper characterization is required. This work undertakes it using advanced instrumentation and methods.PROBE Cost Action - NASA Ra-diation Sciences Program and Earth Observing System UIDB/04683/2020National funds through FCT -Fundacao para a Ciencia e Tecnologia, I.P., in the framework of the ICT project UIDB/04683/2020 UIDP/04683/2020TOMA-QAPA PTDC/CTAMET/29678/2017GRASP-ACE 778349ACTRIS-IMP 871115ATMO-ACCESS 101008004PROBE CA18235HARMONIA CA21119EUMETNET through the E-PROFILE program and REALISTIC 101086690ACTRIS-2 654109Spanish Government PID2019-103886RB-I00/AEI/10.13039/501100011033NTEGRATYON3 PID2020-117825GB-C21 PID2020-117825GB- C22ELPIS PID2020-120015RB-I00CLARIN CGL2016-81092-REPOLAAR RTI2018-097864-B-I00CAMELIA PID2019-104205GB- C21/AEI/10.13039/501100011033ACTRIS-Espa ~na CGL2017- 90884REDTUniversity of Granada Plan Propio through Singular Laboratory LS2022-1Andalusia Autonomous Government projects AEROPRE and ADAPNE P18-RT-3820 P20_00136UGR-FEDER projects DEM3TRIOS A-RNM-524-UGR20MOGATRACO UCE-PP2017-02Scientific Units of Excellence Program RTI 2018-097332-B-C22R+D+i grant MCIN/AEI/ 10.13039/ 501100011033ERDF A Way of Doing EuropeINTA predoctoral contract program A-RNM-430-UGR2

Seasonal analysis of the atmosphere during five years by using microwave radiometry over a mid-latitude site

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-2409Spanish Ministry of Economy and Competitiveness through projects CGL2013-45410-R, CGL2015-73250-JIN and CGL2016-81092-RJuan de la Cierva grant IJCI-2016-3000