Trend Assessment of Global, UVB, UVA Irradiation and Dry Bulb Temperature at the Lowest Terrestrial Site on Earth: Dead Sea, Israel

The Dead Sea basin is lowest terrestrial site on the globe. A meteorological station monitoring the global, UVB and UVA irradiation and the dry bulb temperature was established in 1995 in conjunction with a study of bio-climatological properties of the region with regard to photoclimatherapy treatment of dermatological diseases. The availability of such irradiation and dry bulb temperature databases has been utilized to perform a study to determine if any trends regarding either irradiation or dry bulb temperature exist at this unique site. There was no indication of any trends, based upon a p-value analysis, regarding the global, UVB and UVA irradiation. The global irradiation database included the time interval 1995-2020; whereas the corresponding time interval for the UVB and UVA irradiation databases was 1995-2018. The dry bulb temperature database consisted of the time interval 1995-2020 and, once again, no trends were observed throughout the year with the exception of the nocturnal time interval, between 18:00 to 06:00, during the month of October which exhibited a warming trend of 0.78°C/decade

Modelling and Prediction of Monthly Global Irradiation Using Different Prediction Models

Different prediction models (multiple linear regression, vector support machines, artificial neural networks and random forests) are applied to model the monthly global irradiation (MGI) from different input variables (latitude, longitude and altitude of meteorological station, month, average temperatures, among others) of different areas of Galicia (Spain). The models were trained, validated and queried using data from three stations, and each best model was checked in two independent stations. The results obtained confirmed that the best methodology is the ANN model which presents the lowest RMSE value in the validation and querying phases 1226 kJ/(m2∙day) and 1136 kJ/(m2∙day), respectively, and predict conveniently for independent stations, 2013 kJ/(m2∙day) and 2094 kJ/(m2∙day), respectively. Given the good results obtained, it is convenient to continue with the design of artificial neural networks applied to the analysis of monthly global irradiation.

Direct assessment of the sensitivity drift of SQM sensors installed outdoors

Long-term monitoring of the evolution of the artificial night sky brightness is a key tool for developing science-informed public policies and assessing the efficacy of light pollution mitigation measures. Detecting the underlying artificial brightness trend is a challenging task, since the typical night sky brightness signal shows a large variability with characteristic time scales ranging from seconds to years. In order to effectively isolate the weak signature of the effect of interest, determining the potential long term drifts of the radiance sensing systems is crucial. If these drifts can be adequately characterized, the raw measurements could be easily corrected for them and transformed to a consistent scale. In this short note we report on the progressive darkening of the signal recorded by SQM detectors belonging to several monitoring networks, permanently installed outdoors for periods ranging from several months to several years. The sensitivity drifts were estimated by means of parallel measurements made at the beginning and at the end of the evaluation periods using reference detectors of the same kind that were little or no exposed to weathering in the intervening time. Our preliminary results suggest that SQM detectors installed outdoors steadily increase their readings at an average rate of +0.034 magSQM/arcsec2 per MWh/m2 of exposure to solar horizontal global irradiation, that for our locations translates into approximately +0.05 to +0.06 magSQM/arcsec2 per year.

Solar Radiation on a Parabolic Concave Surface

Curved structures are used in buildings and may be integrated with photovoltaic modules. Self-shading occurs on non-flat (curved) surface collectors resulting in a non-uniform distribution of the direct beam and the diffuse incident solar radiation along the curvature the surface. The present study uses analytical expressions for calculating and analyzing the incident solar radiation on a general parabolic concave surface. Concave surfaces facing north, south and east/west are considered, and numerical values for the annual incident irradiations (in kWh) are demonstrated for two locations: 32° N (Tel Aviv, Israel) and 52.2° N (Lindenberg, Germany). The numerical results show that the difference in the incident global irradiation for the different surface orientations is not very wide. At 32° N, the irradiation difference between the south and north-oriented surface is about 15 percent, and between the south and east surface orientation it is about 9.6 percent. For latitude 52.2° N, the global irradiation difference between the south and north-oriented surface is about 16 percent, and between the south and east orientation it is about 3 percent.

Modelling Using Machine Learning Models and Prediction of Monthly Global Irradiation

Different machine learning models (multiple linear regression, vector support machines, artificial neural networks and random forests) are applied to predict the monthly global irradiation (MGI) from different input variables (latitude, longitude and altitude of meteorological station, month, average temperatures, among others) of different areas of Galicia (Spain). The models were trained, validated and queried using data from three stations, and each best machine model was checked in two independent stations. The results obtained confirmed that the best ML methodology is the ANN model which presents the lowest RMSE value in the validation and querying phases 122.6·10kJ/(m2∙day) and 113.6·10kJ/(m2∙day), respectively, and predict conveniently for independent stations, 201.3·10kJ/(m2∙day) and 209.4·10kJ/(m2∙day), respectively. Given the good results obtained, it is convenient to continue with the design of artificial neural networks applied to the analysis of monthly global irradiation.

Correction of Shading Effects on Different Components of Solar Radiation

There have been many published articles describingshading effect algorithms for solar irradiation mapping indifferent components, that enabling scientists to gain experiencewith new techniques at low cost. The maps for diffuse, direct and global Solar irradiation havebeen calculated in combination satellite image data (Input data insystem) for a shorter period of one day. structured together usingthe “Inverse distance to a power” interpolation method.The Global and Diffuse irradiation maps were calculated with analgorithm based for correcting shading effects related to theorography estimated in Horizontal Plane and evaluate it on anyinclined plane using the sky brightness and clearness index andthe relative optical attenuation factor of the atmosphericthickness. The Direct irradiation is mapped as the combinationbetween global and diffuse irradiation. The tests of this methodwere carried out on several large sites, and showed good results.Keyword: Direct and global irradiation, Diffuse circumsolar andisotropic, index of shading effect