Cloud Shadows in Satellite-based Solar Irradiance Estimation: Improved Correction using EUMETSAT's Cloud Top Height Data

The estimation of solar surface irradiance at high spatio-temporal resolution from geo-stationary satellite images is a well-established technique, for example by using the Heliosat method. The method has widely reduced the need for expensive ground measurements, especially in remote regions. However, the location of cloud shadows at the ground is difficult to determine and thus a significant source of errors when either the distance from the sub-satellite point or the cloud top height (CTH) increases. Although several methods have been proposed in the literature to reduce these errors, it is still an issue. We present a novel approach to correct the cloud shadow location based on the satellite-cloud-sun geometry using the CTH maps from the EUMETSAT data archive. It uses satellite viewing angles and solar position angles to determine the correct cloud shadow location for each cloudy pixel. The method is tested on cloud index (CI) maps for the months of July, August and September 2018 derived by applying the Heliosat method on the 0.6 um visible channel images from Meteosat-8 located at 41.5°E. Convective clouds with large CTHs are frequently observed over the Indian subcontinent in these three months due to the Indian summer monsoon. The global horizontal solar irradiance (GHI) obtained from the corrected CI image is validated at two BSRN stations. The normalized root mean square error (nRMSE) is reduced from 23.2% to 20.9% for the Gurgaon station and from 15.4% to 13.9% at Tiruvallur. In general, correcting the cloud shadow location on CI map improved the accuracy of the estimated GHI. Nonetheless, the method is sensitive to the accuracy of the CTH dataset and individual cases were found for which the correction reduced the accuracy

Impact of tropical convective conditions on solar irradiance forecasting based on cloud motion vectors

Intra-day forecasts of global horizontal solar irradiance (GHI) are widely produced by displacing existing clouds on a geo-stationary satellite image to their future locations with cloud motion vectors (CMVs) derived from preceding images. The CMV estimation methods assume rigid cloud bodies with advective motion, which performs reasonably well in mid-latitudes but can be strained for tropical and sub-tropical climatic zones during prolonged periods of seasonal convection. We study the impact of the South Asian monsoon time convection on the accuracy of CMV based forecasts by analysing 2 years of forecasts from three commonly used CMV methods—Block-match, Farnebäck (Optical flow) and TV-L1 (Optical flow). Forecasted cloud index (CI) maps of the entire image section are validated against analysis CI maps for the period 2018–2019 for forecast lead times from 0 to 5.5 h. Site-level GHI forecasts are validated against ground measured data from two Baseline Surface Radiation Network stations—Gurgaon (GUR) and Tiruvallur (TIR), located in hot semi-arid and tropical savanna climatic zones respectively. The inter-seasonal variation of forecast accuracy is prominent and a clear link is found between the increase in convection, represented by a decrease in outgoing longwave radiation (OLR), and the decrease in forecast accuracy. The GUR site shows the highest forecast error in the southwest monsoon period and exhibits a steep rise of forecast error with the increase in convection. The highest forecast error occurs in the northeast monsoon period of December in TIR. The impact of convection on the number of erroneous time blocks of predicted photovoltaic production is also studied. Our results provide insights into the contribution of convection to errors in CMV based forecasts and shows that OLR can be used as a feature in future forecasting methods to consider the impact of convection on forecast accuracy

Preliminary Report on the Consequences of LHC Civil Engineering for the SPS and LEP

The excavation of the shafts and caverns for the ATLAS and CMS experiments of the LHC will start whilst LEP and the SPS are running. This will be at a period when LEP should be at its peak performance and the SPS will be providing beams for LEP, fixed target physics and LHC test beams. Simulations show that movements of the machine tunnels can be expected during the excavation and it is essential that this does not affect the performance of the SPS and LEP. These movements are of sufficient amplitude to prevent machine operation if no precautions are taken. This preliminary report outlines the problems and suggests what actions should be taken to ensure efficient operation of the SPS and LEP during the critical period

Relationships between antioxidants, antioxidant enzyme activities and lipid peroxidation products during early development in Dentex dentex eggs and larvae

The overall aim is the characterization of the antioxidant systems in marine fish during early development in order to enhance growth and quality of early life stages by avoiding oxidation problems that may cause pathologies and disease. The present study determined the activities of the antioxidant system enzymes and levels of vitamin E, lipid peroxidation products and fatty acids during early development without exogenous feeding in the marine fish, Dentex dentex. Samples of fertilized eggs just prior to hatch, newly hatched larvae and unfed larvae up to day 9 after hatch were analysed on a daily basis. The larvae did not grow during the experiment and by day 9 the surviving larvae weighed only a third of the newly hatched larvae. Lipid was a major energy source during this period of starvation as evidenced by greatly decreased amounts of total lipid due to a preferential utilisation of neutral lipids. All groups of fatty acids (saturated, monounsaturated and polyunsaturated) were consumed throughout the starvation period. Vitamin E levels were relatively constant until significantly declining by days 8 and 9. Similarly, levels of lipid-soluble fluorescent products (LSFP) were relatively constant until day 6 and then significantly decreased from days 7 to 9. In contrast, the level of malondialdehyde (MDA) was very high in eggs but was 3-fold lower in newly hatched larvae and then decreased over the whole time-course and was also significantly lower on days 8 and 9. The activities of enzymes of the antioxidation system were expressed in both eggs and early larvae and varied during the developmental period with levels of catalase and glutathione peroxidase (GPX) being initially low in eggs whereas glutathione-S-transferase (GST) and superoxide dismutase (SOD) were higher in eggs than in larvae. Overall, the activities of catalase and GPX increased, whereas GST and total SOD activities decreased, during the early stages of development during a period where there was no exogenous dietary input into the larvae. Glutathione reductase activity was very low and showed an increasing trend initially until days 2-3 before declining and varying over the remaining period. In conclusion, we determined the prooxidant (polyunsaturated fatty acid) status, antioxidant status (vitamin E), peroxidation status (MDA and LSFP) and the activities of the antioxidant enzyme systems in a single integrated study in unfed marine fish larvae during early development

Use of the Generalized Gradient Approximation in Pseudopotential Calculations of Solids

We present a study of the equilibrium properties of $sp$-bonded solids within the pseudopotential approach, employing recently proposed generalized gradient approximation (GGA) exchange correlation functionals. We analyze the effects of the gradient corrections on the behavior of the pseudopotentials and discuss possible approaches for constructing pseudopotentials self-consistently in the context of gradient corrected functionals. The calculated equilibrium properties of solids using the GGA functionals are compared to the ones obtained through the local density approximation (LDA) and to experimental data. A significant improvement over the LDA results is achieved with the use of the GGA functionals for cohesive energies. For the lattice constant, the same accuracy as in LDA can be obtained when the nonlinear coupling between core and valence electrons introduced by the exchange correlation functionals is properly taken into account. However, GGA functionals give bulk moduli that are too small compared to experiment.Comment: 15 pages, latex, no figure

Help-seeking among Male Farmers: Connecting Masculinities and Mental Health

In many ways, male farmers can be considered to be a vulnerable group in relation to mental health, experiencing high rates of suicide, psychological distress and low use of health services. This study highlights important connections between rurality, farming and masculinities in the context of men's mental health. In-depth interviews with 32 male farmers from Quebec, Canada were completed focusing on stress and coping strategies. Findings include informal and formal strategies. Many participants had previous positive experience of formal help and would be willing to use such help again and to recommend it to others in need. Those without such experience are sceptical about services but recognise the courage it requires to seek help. Pride and lack of knowledge about services are the main barriers to help-seeking, but it can be legitimated in certain contexts, such as divorce or other psychosocial crisis, and by alignment with particular male ideals. Role models at national or local levels can also help farmers prioritise their own and their family's wellbeing over stigmas and rigid, traditional masculine ideals. Furthermore, gender-based strengths and recommendations for practice are also discussed

Thinking globally, working locally: employability and internationalization at home

As an approach to the internationalization of higher education, Internationalization at Home (IaH) looks beyond the mobility of a minority of students, emphasizing instead the delivery to all students of an internationally focused curriculum and the embedding of intercultural communication. This can be expanded to include extracurricular activities and building relationships with local cultural and ethnic community groups. The MA in international development at Nottingham Trent University, United Kingdom, has implemented this approach, looking beyond both mobility and curriculum to apply IaH directly to student employability, embracing intercultural competence as a key professional skill. This article explores the efficacy of this combination in the MA’s professional development pathway, which requires students to complete a placement, which demonstrates international and intercultural engagement, usually undertaken “at home,” and to critically reflect not just on their professional skills, but on their ability to engage in the ethical practice, which is a key element of IaH

Observing Clouds from above and below - a chance for Redispatch 2.0?

Balancing the power production and energy demand is a constant activity of electricity grid operators. Since October 2021, distribution system operators (DSO) in Germany have a completely new role in redispatch as they have now to collaborate more actively with transmission grid operators (TSO) in their daily operations. Important new tasks of the DSO in the Redispatch 2.0 are now the use of daily feed-in forecasts, ensuring the network effectiveness and calculating flexibility restrictions on grid node levels. For these tasks they need to know the photovoltaic power feed in the next minutes and hours. DLR’s high resolution hybrid irradiance forecast is currently based on the combination of a Meteosat satellite derived forecast (based on the Heliosat 3 method) and forecasts derived from the All Sky Imager (ASI) network Eye2Sky. DLR’s Eye2Sky is a cloud monitoring system covering roughly 110x100 km in north-west Germany. It is equipped with 38 all sky imagers, i.e. sky-facing fisheye cameras, ten solar irradiance measurement stations and two individual instruments for cloud height measurement (Ceilometer) distributed throughout the region. The system collects high-resolution information on solar irradiance , tracks the variability and provides forecasts for very short time scales. It has a spatial resolution 50 meters and the temporal resolution exceeds 1 minute. It can produce forecasts for up to one hour ahead depending on the prevailing cloud height and velocity. The data can inform about present and future weather (solar irradiance) conditions for the reliable operation of distribution grids, and economic operation of solar installations as well as for regional case studies. Outcomes of the Smart4RES project show that the hybrid forecast outperforms the RMSE of persistence and the individual input forecasts for all lead times (5min to 30min) for a first validation period of two months (July and August 2020). So, it is a promising candidate for assisting DSOs in their new tasks in Redispatch 2.0. Coupling cloud observations from above (satellite) and below (ground observations) combines the pros and cons of each observing system. We further analyze the cloud situation dependent accuracy of the forecast methods and assess the impact of the assumptions in satellite retrievals on their performances

Improving the satellite retrieval of surface solar irradiance during an eclipse

Solar eclipse causes high magnitude fluctuations in the Surface Solar Irradiance (SSI) for a short duration and consequently reduces the output of solar PV systems. Grid operators try to estimate the impending loss in PV power generation prior to the occurrence of an eclipse in order to schedule conventional generators for compensating the loss. The worldwide installed capacity of grid connected solar PV systems is expected to steeply rise in the coming decade as a result of the various policy initiatives aimed to tackle the climate change. In future electric supply networks with a high penetration of solar PV systems, such large ramps in generation could impact the stability of the network. Although a solar eclipse is a purely deterministic phenomenon, it’s impact on the satellite retrieval of Surface Solar Irradiance (SSI) is complicated due to the possibility of cloud presence in the regions affected by the eclipse. The extraterrestrial solar irradiance is reduced by the moon during an eclipse. On the one hand this causes clouds to appear darker and they get assigned lower reflectance values than they should have in reality. This leads to predicting higher values for the solar irradiance under these clouds than expected. On the other hand, the eclipse also reduces the clear sky irradiance reaching the earth surface. We developed a method to make corrections for both of these effects on the High Resolution Visible (HRV) channel images from Meteosat-11 The results are validated against ground measurements of irradiance provided by BSRN, IEA-PVPS, DTN and the National Weather Services networks. The validation is performed for sites with locations across Europe and for the last two eclipses