Analysis of Spatial and Temporal Variability of the PAR/GHI Ratio and PAR Modeling Based on Two Satellite Estimates

The main objectives of this work are to address the analysis of the spatial and temporal variability of the ratio between photosynthetically active radiation (PAR) and global horizontal irradiance (GHI), as well as to develop PAR models. The analysis was carried out using data from three stations located in mainland Spain covering three climates: oceanic, standard Mediterranean, and continental Mediterranean. The results of this analysis showed a clear dependence between the PAR/GHI ratio and the location; the oceanic climate showed higher values of PAR/GHI compared with Mediterranean climates. Further, the temporal variability of PAR/GHI was conditioned by the variability of clearness index, so it was also higher in oceanic than in Mediterranean climates. On the other hand, Climate Monitoring Satellite Facility (CM-SAF) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data were used to estimate PAR as a function of GHI over the whole territory. The validation with ground measurements showed better performance of the MODIS-estimates-derived model for the oceanic climate (root-mean-square error (RMSE) around 5%), while the model obtained from CM-SAF fitted better for Mediterranean climates (RMSEs around 2%)This work was funded by the Ministry of Economy, Industry and Competitiveness (MINECO) [Project CGL2016-79284-P AEI/FEDER/UE and F.F.-C. was founded by PhD Contract Number BES-2017-082043]S

Desarrollo de una Red de Medidas y Modelización de la Radiación Fotosintéticamente Activa

Este trabajo tiene dos objetivos. El primero consiste en la planificación y el montaje de una red de medidas de radiación fotosintéticamente activa (PAR) en España. El segundo es el desarrollo de modelos de la radiación PAR para España, complementariamente, se elaborarán mapas de radiación PAR. La red de medidas de radiación PAR consta de nueve estaciones, dos de las cuales ya se encontraban operativas al inicio del proyecto. Para el montaje e instalación de las mismas se alcanzaron acuerdos de colaboración con siete instituciones que amablemente nos cedieron espacio para su montaje. Las estaciones están plenamente operativas desde mayo de 2019. En este trabajo, se presentan cuatro metodologías para la elaboración de modelos de radiación PAR. La primera propone el desarrollo de modelos desde un punto de vista regional. Para regionalizar el territorio de estudio, se realiza un análisis clúster que determina las zonas que se comportan de manera similar frente a la radiación PAR. Con esta metodología se han elaborado modelos diarios y horarios. La segunda aborda la modelización de la radiación PAR localmente, proponiendo un modelo para cada punto del área de estudio. La tercera, consiste en la corrección de un modelo previo utilizando la técnica site-adaptation y medidas de tierra. En cambio, la última aborda el desarrollo de un modelo compuesto. Este modelo se elabora como una combinación lineal de las estimaciones de los modelos locales a partir de datos medidos en las estaciones pertenecientes a la red de medidas PAR. Finalmente, se evalúa la actuación de los mejores modelos de cada metodología con los datos proporcionados por las estaciones de la red de medidas PAR, para determinar cuál de todos ellos es el más preciso, y, por lo tanto, el más adecuado para utilizarlo en la elaboración de los mapas de radiación PAR sobre España. Posteriormente, se presentan mapas mensuales, trimestrales y uno anual de radiación PAR media diaria sobre el territorio de estudio. Este trabajo presenta varias novedades. En primer lugar se ha instalado una red de nueve estaciones que proporcionan medidas minutales de PAR, que constituye la primera red de medidas PAR desplegada por todo el territorio peninsular de España. Otra aportación novedosa es la elaboración de modelos de radiación PAR para el conjunto del área peninsular de España, ya que los precedentes de la bibliografía se basan en modelos locales y no se había abordado la modelización de todo el territorio en su conjunto. También se presenta un novedoso índice basado en las probabilidades de excedencia para estimar la bondad de un modelo (válido para modelos de radiación PAR y cualquier otra variable que se desee modelar). ----------ABSTRACT---------- This work has two objectives. The first one consists of planning and setting up a network for measurements of photosynthetically active radiation (PAR) in Spain. The second is the development of PAR models for Spain. In addition, PAR maps over Spain will be elaborated. The network of PAR measurements has nine stations, two of which were already operating at the beginning of the project. Collaboration agreements were reached with seven institutions that kindly cede space for the assembly of the stations, which have been fully operational since May 2019. In the present work, four methodologies for elaborating PAR models are presented. The first one proposes the development of PAR models from a regional point of view. To regionalize the territory of study, a cluster analysis is carried out to determine the areas that behave similarly towards PAR. Daily and hourly PAR models have been developed using this methodology. The second one addresses the local modeling of PAR, proposing a model for each point of the territory of study. The third one consists of correcting a previous model using the site-adaptation technique and ground measurements. The last methodology deals with the development of a compound model. This model is elaborated as a linear combination of the estimates of the local models calculated from data measured in the stations belonging to the PAR measurement network. Finally, to determine which of them is the most accurate, and therefore the most suitable to use in the elaboration of the PAR maps over Spain, the performance of the best models of each methodology is evaluated with data provided by the stations of the PAR measurement network. Subsequently, monthly, quarterly and annual maps of average daily PAR over the study territory are presented. This work introduces several novelties. In the first place, a network of nine stations that provide minute PAR measurements have been installed, which constitutes the first network of PAR measurements deployed throughout mainland Spain. Another novel contribution is the elaboration of PAR models for mainland Spain as a whole, since the precedents of the bibliography are based on local models and the modeling of the entire territory had not been addressed. A novel index based on exceedance probabilities to estimate the goodness of a model (valid for PAR models as well as for any other variable whose modeling is intended) is presented as well

Combination of Models to Generate the First PAR Maps for Spain

This work addresses the development of a PAR model in the entire territory of mainland Spain. Thus, a specific model is developed for each location of the study field. The new PAR model consists of a combination of the estimates of two previous models that had unequal performances in different climates. In fact, one of them showed better results with Mediterranean climate, whereas the other obtained better results under oceanic climate. Interestingly, the new PAR model showed similar performance when validated at seven stations in mainland Spain with Mediterranean or oceanic climate. Furthermore, all validation slopes ranged from 0.99 to 1.00; the intercepts were less than 3.70 μmol m−2 s−1; the R2 were greater than 0.988, while MBE was closer to zero percent than −0.39%; and RMSE were less than 6.21%. The estimates of the PAR model introduced in this work were then used to develop PAR maps over mainland Spain that represent daily PAR averages of each month and a full year at all locations in the study field

A New Index Assessing the Viability of PAR Application Projects Used to Validate PAR Models

Photosynthetically active radiation (PAR) is a useful variable to estimate the growth of biomass or microalgae. However, it is not always feasible to access PAR measurements; in this work, two sets of nine hourly PAR models were developed. These models were estimated for mainland Spain from satellite data, using multilinear regressions and artificial neural networks. The variables utilized were combinations of global horizontal irradiance, clearness index, solar zenith angle cosine, relative humidity, and air temperature. The study territory was divided into regions with similar features regarding PAR through clustering of the PAR clearness index (kPAR). This methodology allowed PAR modeling for the two main climatic regions in mainland Spain (Oceanic and Mediterranean). MODIS 3 h data were employed to train the models, and PAR data registered in seven stations across Spain were used for validation. Usual validation indices assess the extent to which the models reproduce the observed data. However, none of those indices considers the exceedance probabilities, which allow the assessment of the viability of projects based on the data to be modeled. In this work, a new validation index based on these probabilities is presented. Hence, its use, along with the other indices, provides a double and thus more complete validation

Combination of models to generate the first PAR maps for Spain

14 p.-7 fig.-5 tab.This work addresses the development of a PAR model in the entire territory of mainland Spain. Thus, a specific model is developed for each location of the study field. The new PAR model consists of a combination of the estimates of two previous models that had unequal performances in different climates. In fact, one of them showed better results with Mediterranean climate, whereas the other obtained better results under oceanic climate. Interestingly, the new PAR model showed similar performance when validated at seven stations in mainland Spain with Mediterranean or oceanic climate. Furthermore, all validation slopes ranged from 0.99 to 1.00; the intercepts were less than 3.70 μmol m−2 s−1; the R2 were greater than 0.988, while MBE was closer to zero percent than −0.39%; and RMSE were less than 6.21%. The estimates of the PAR model introduced in this work were then used to develop PAR maps over mainland Spain that represent daily PAR averages of each month and a full year at all locations in the study field.The authors would like to thank the funding from the Ministry of Economy, Industry, and Competitiveness (MINECO) (Project CGL2016-79284-P AEI/FEDER/UE). FF-C acknowledges its funding to MINECO for its grant (BES-2017-082043), and also to the Autonomous Community of Madrid, Spain, and co-financed by the FEDER “A way of making Europe” ALGATEC-CM (S2018/BAA-4532) and to the CYTED-IberoAmerican Program on Science and Technology for Development (Red RENUWAL P320RT0005 CYTED).Peer reviewe

Generation of typical meteorological sequences to simulate growth and production of biological systems

16 p.-5 fig.-6 tab.Numerical simulation applied to agriculture or wastewater treatment (WWT) is a complementary tool to understand, a priori, the impact of meteorological parameters on productivity under limiting environmental conditions or even to guide investments towards other more relevant circular economic objectives. This work proposes a new methodology to calculate Typical Meteorological Sequences (TMS) that could be used as input data to simulate the growth and productivity of photosynthetic organisms in different biological systems, such as a High-Rate Algae Pond (HRAP) for WWT or in agriculture for crops. The TMS was established by applying Finkelstein-Schafer statistics and represents the most likely meteorological sequence in the long term for each meteorological season. In our case study, 18 locations in the Madrid (Spain) region are estimated depending on climate conditions represented by solar irradiance and temperature. The parameters selected for generating TMS were photosynthetically active radiation, solar day length, maximum, minimum, mean, and temperature range. The selection of potential sequences according to the growth period of the organism is performed by resampling the available meteorological data, which, in this case study, increases the number of candidate sequences by 700%.This research was funded by the Autonomous Community of Madrid, Spain, and financed by FEDER ‘A way of making Europe’ ALGATEC-CM (S2018/BAA-4532) and by the Spanish Ministry of Science and Innovation (MCIN/AEI/10.13039/501100011033) and the European Union “Next Generation EU”/PRTR, TEDDY (TED2021-130366B-I00).Peer reviewe

Comparative analysis of photosynthetically active radiation models based on radiometric attributes in mainland Spain

25 p.-12 fig.-4 tab.The aims of this work are to present an analysis of quality solar radiation data and develop several hourly models of photosynthetically active radiation (PAR) using combinations of radiometric variables such as global horizontal irradiance (GHI), diffuse horizontal irradiance (DHI), and direct normal irradiance (DNI) from their dimensionless indices atmospheric clearness index (kt ), horizontal diffuse fraction (kd ), and normal direct fraction (kb ) together with solar elevation angle (α ). GHI, DHI, and DNI data with 1-minute frequencies in the period from 2016 to 2021 from CEDER-CIEMAT, in a northern plateau, and PSA-CIEMAT in the southeast of the Iberian Peninsula, were used to compare two locations with very different climates according to the Köppen—Geiger classification. A total of 15 multilinear models were fitted and validated (with independent training and validation data) using first the whole dataset and then by kt intervals. In most cases, models including the clearness index showed better performance, and among them, models that also use the solar elevation angle as a variable obtained remarkable results. Additionally, according to the statistical validation, these models presented good results when they were compared with models in the bibliography. Finally, the model validation statistics indicate a better performance of the interval models than the complete models.This research was funded by the Autonomous Community of Madrid, Spain, and was cofinanced by FEDER ‘A way of making Europe’ ALGATEC-CM (S2018/BAA-4532).Peer reviewe