Solar radiation characteristics at Qena / Egypt

Measurements of the hourly global solar radiation (G) and its diffuse component (D) on a horizontal surface have been carried out in Qena / Upper Egypt in the period from June 1992 to May 1993. The corresponding diffuse fraction (DIG) is calculated. Diurnal variations of the results have been studied. Also the daily totals values and its monthly and seasonal averages as well as their frequency distributions were computed and examined. The seasonal and climatic effects on the fluctuation of the results are discussed. These effects were particularly large during spring and Winter months owing to the high fluctuation of the atmospheric conditions with aspect to amount of clouds, water content, and concentration of aerosol dust particles. The influence of clouds is also considered. It shows small effect on the results (4.5%), reflecting the low degree of cloudiness in the study region. The relation between the diffuse fraction and clearness index (G/Go) shows that most of the points lies in the region of the high availability of the incoming solar radiation. In general the study shows clearly the abundance of solar energy in Qena / Egypt, and the suitability of its climate for using it in different applications.

Development of micro- and nanoindentation methods for assessing the mechanical properties of coals and their propensity to destruction

The destruction of coals in the processes of mining, storage, transportation and processing is associated, among other, with their mechanical properties. As a rule, the mechanical properties of coals are evaluated by the resul ts of measurements of such characteristics as tensile and compressive strength, stiffness (elastic modulus) and Poisson’s ratio, etc. For this, experiments are carried out on specially prepared samples in tensile testing machines and mechanical presses. Such integral indicators characterize the mechanical behavior of coals at the macro scale and do not allow assessing the influence of structural features on the initiation of defects leading to destruction. In this regard, the characteristics of the mechanical properties of coals, obtained in areas comparable to the levels of microcracks initiation, are of interest. Micro- and nanoindentation techniques are quite simple to implement for obtaining the reliable information on various mechanical properties of materials at the appropriate scale levels. This paper is dedicated to an overview of the current state of research on the use of these methods to assess the mechanical properties of coals and their individual macerals, as well as their ability to crush with the formation of dust particles. The use of micro- and nanoindentation techniques made it possible to establish the differences in the mechanical properties of individual macerals of coals, as well as to characterize the heterogeneity of the distribution of various indicators characterizing mechanical properties within the individual macerals. Based on experimental data on nanoindentation and Raman spectroscopy, it was shown that the change in the mechanical properties (values of the modulus of elasticity and hardness) of vitrinite in the series of coal metamorphism is associated with an increase in the proportion of graphitized components in organic matter. Nanoindentation methods, combined with an analytical mathematical apparatus, made it possible to obtain data on the ability of coals to crush under mechanical effects with the formation of particles with sizes comparable to those of hazardous aerosol dust (class PM 2.5). The method of cyclic nanoindentation with an increasing maximum load was proposed as a method for determining the degree of coal tendency to fracture with the formation of dust. Its application made it possible to reveal the characteristics of irreversible changes occurring in the structure of coals during destruction. They are expressed in a change in their mechanical properties (stiffness and fracturing ability) with an increase in the applied load. The use of the cyclic nanoindentation method is a promising method for the qualitative and quantitative analysis of the degree of coal propensity to crushing with the formation of dust. This work was carried out with the financial support of the Russian Science Foundation (Grant No. 18-77-10052).

Bio-Aerosols Negatively Affect Prochlorococcus in Oligotrophic Aerosol-Rich Marine Regions

The marine cyanobacterium Prochlorococcus is a dominant photoautotroph in many oligotrophic Low-Nutrients-Low-Chlorophyll (LNLC) regions. While the chemical impact of aerosols upon interaction with surface seawater was documented in numerous studies, we show that Prochlorococcus cells are affected also by bio-aerosols (potentially biological agents in the dust/aerosols such as membrane-bound extracellular vesicles, small-size bacteria and/or viruses), resulting in lower surface seawater abundances in the oligotrophic Mediterranean Sea. We conducted experimental amendments of ‘live’ aerosol/dust particles and aerosol filtrates (<0.22-µm) to surface Southeastern Mediterranean seawater or to pure Prochlorococcus cultures (MED4). Results show a significant decline in cell biomass (<90%), while UV-sterilized aerosols elicited a much weaker and non-significant response (~10%). We suggest that the difference is due to a negative effect of bio-aerosols specific to Prochlorococcus. Accordingly, the dominance of Synechococcus over Prochlorococcus throughout the surface Mediterranean Sea (observed mainly in spring when atmospheric aerosol levels are relatively high) and the lack of spatial westward gradient in Prochlorococcus biomass as typically observed for chlorophyll-a or other cyanobacteria may be attributed, at least to some extent, to the impact of bio-aerosol deposition across the basin. Predictions for enhanced desertification and increased dust emissions may intensify the transport and potential impact of bio-aerosols in LNLC marine systems.

Electro-optical dust sensors calibration by aerosol image analysis

The paper describes the process of data obtaining for designing electro-optical sensors using a television aerosol particles image analyzer. Using simulation based on Mie theory, the process of calibration of simple electro-optical aerosol (dust) sensor is carried out. In the paper the main dependences for sensor calibration are shown. The proper calibration allows power saving by selection certain laser beam power level.

Sensitivity of the interannual variability of mineral aerosol simulations to meteorological forcing dataset

Interannual variability in desert dust is widely observed and simulated, yet the sensitivity of these desert dust simulations to a particular meteorological dataset, as well as a particular model construction, is not well known. Here we use version 4 of the Community Atmospheric Model (CAM4) with the Community Earth System Model (CESM) to simulate dust forced by three different reanalysis meteorological datasets for the period 1990–2005. We then contrast the results of these simulations with dust simulated using online winds dynamically generated from sea surface temperatures, as well as with simulations conducted using other modeling frameworks but the same meteorological forcings, in order to determine the sensitivity of climate model output to the specific reanalysis dataset used. For the seven cases considered in our study, the different model configurations are able to simulate the annual mean of the global dust cycle, seasonality and interannual variability approximately equally well (or poorly) at the limited observational sites available. Overall, aerosol dust-source strength has remained fairly constant during the time period from 1990 to 2005, although there is strong seasonal and some interannual variability simulated in the models and seen in the observations over this time period. Model interannual variability comparisons to observations, as well as comparisons between models, suggest that interannual variability in dust is still difficult to simulate accurately, with averaged correlation coefficients of 0.1 to 0.6. Because of the large variability, at least 1 year of observations at most sites are needed to correctly observe the mean, but in some regions, particularly the remote oceans of the Southern Hemisphere, where interannual variability may be larger than in the Northern Hemisphere, 2–3 years of data are likely to be needed.

Sensitivity of the Variability of Mineral Aerosol Simulations to Meteorological Forcing Datasets

Interannual variability in desert dust is widely observed and simulated, yet the sensitivity of these desert dust simulations to a particular meteorological dataset, as well as a particular model construction, is not well known. Here we use version 4 of the Community Atmospheric Model (CAM4) with the Community Earth System Model (CESM) to simulate dust forced by three different reanalysis meteorological datasets for the period 1990–2005. We then contrast the results of these simulations with dust simulated using online winds dynamically generated from sea surface temperatures, as well as with simulations conducted using other modeling frameworks but the same meteorological forcings, in order to determine the sensitivity of climate model output to the specific reanalysis dataset used. For the seven cases considered in our study, the different model configurations are able to simulate the annual mean of the global dust cycle, seasonality and interannual variability approximately equally well at the limited observational sites available. Overall, aerosol dust source strength has remained fairly constant during the time period from 1990 to 2005, although there is strong seasonal and some interannual variability simulated in the models and seen in the observations over this time period. The models predict similar seasonal variability and timing as one another, and obtain the best comparison to observations at the seasonal scale. Interannual variability comparisons to observations, as well as comparisons between models, suggest that interannual variability in dust is still difficult to simulate accurately, with averaged correlation coefficients of 0.1 to 0.6. Because of the large variability, at least one year of observations at most sites are needed to correctly observe the mean, but in some regions, particularly the remote oceans of the Southern Hemisphere, where interannual variability appears to be larger, 2–3 years of data are needed.