To reveal variations in the iso topic composition of O and H in the atmospheric precipitation in Moscow and the processes influencing the isotope composition, all events of precipitation in 2017-2019 were sampled at the Meteorological Observatory of the Moscow State University: 158 samples in 2017, 119 samples in 2018 and 143 samples in 2019. The study is a prolongation of continuous measurements of the isotope composition of precipitation, started by authors in 2014. The study of the isotope composition of precipitation at the MSU Meteorological Observatory was supported by the IAEA and became a part of the Global Network of Isotopes in Precipitation (GNIP) database. It has been found that the intra-annual variability of the isotop e composition of precipitation has a pronounced seasonality. The most isotopically heavy precipitation falls from May to August, and the most isotop ically light precipitation at December-February, mainly due to seasonal air temperature variations. The ratio of the average monthly δ18O values in precipitation and air temperature for the study period varied from 0.34 to 0.39‰/°C, which is consistent with the previously obtained data for precipitation in Moscow. The δ2H-δ18O ratio in precipitation was clos e to that of the Global Meteoric Water Line, pointing to the equilibrium conditions during precipitation formation. It was established that in the summer months isotopic composition is significantly influenced by undercloud evaporation. The deuterium excess va lues in precipitation are not markedly seasonal; however, lower dexc values (below the 3-year average of 11‰) are typical for the summer months (July-August). It is most likely due to undercloud evaporation in conditions of low relative humidity and high air temperatures. Higher dexc values (above 11‰) prevailed from October to April.

— Automated Sun-tracking systems are important elements of solar power devices, which make it possible to increase the amount of solar energy converted to consumer formats during the daylight period, especially true for devices with solar energy concentration. In this study, we investigated the parameters of functioning of the Sun-tracking system built into the photovoltaic thermal installation with parabolic cylindrical concentrators of solar radiation, as well as the main characteristics of the complex as a whole. With attention to the installation structure and tracking system schematics, the studies were carried out on natural solar radiation, with simultaneous measurement of the photovoltaic characteristics and the solar radiation flux density using a pyranometer. The installation parameters were estimated in relation to the angular motion of the Sun across the celestial hemisphere. Due to numerous heterogeneous factors affecting the result, the experimental data were largely statistical in nature. For this reason, the parameters were evaluated using methods of regression analysis. In a number of experimental dependences, the correlation coefficient of the short-circuit current and the solar radiation flux density reached 98%. The studies allowed us to estimate the accuracy of Sun tracking at 1.5–2 angular degrees. In this case, the short-circuit current in the photovoltaic part of the installation varied by ±4% within an hour. In the course of field studies, the fraction of scattered solar radiation was estimated at ~20% of the total intensity. The concentration coefficient of 5.0–5.1 times was calculated from the dependence of the short-circuit current on the solar radiation intensity.

The study was carried out on the basis of all the individual samples (101 cases) of precipitation for 2014, sampled at the Meteorological Observatory of Moscow State University. The concentrations of the main anions and cations, the total mineralization and δ18O values were determined. 12 cases of relatively high mineralization of precipitation were recorded. Average weighted mineralization values ranged from 12.0 to 67.7 mg/L, specific values of mineralization varied from 3.2 to 229.0 mg/L. Chlorine prevails among anions, calcium prevails among cations. The used isotope data analysis and backward trajectories of air masses showed the hydro-chemical composition of precipitation in Moscow not to be linked to the origin of air masses. This indicates to the predominantly urban origin of pollutants in precipitation. In general, in 2014 precipitation were significantly more mineralized than in previous years of observations, due to the climatic conditions of a particular year - small amount of precipitation and number of days with precipitation. This has led to the accumulation of pollutants in the atmosphere and the poor washout of pollutants.

The chemical composition of atmospheric precipitation for the Meteorological Observatory of Moscow University is analyzed basing on the monitoring of every event of wet atmospheric fallout for 1982 to 2017 period. The whole number of observations can be grouped into three periods, which are characterized by different acidity of precipitation, changes in mineralization and the predominance of certain ions. The 1980-1998 period is characterized by the most polluted atmospheric precipitation with high acidity; the 1999-2004 period - by almost complete absence of acid deposition and decrease in mineralization of precipitation. The latest period (2005-2017) is characterized by increasing frequency of acid fallouts, while the mineralization shows no changes despite a significant increase of chlorides in precipitation in recent years. The possible reasons for these trends are discussed. The average long-term pH value was 4,90±0,03 and the mineralization value was 17,1±1,0 mg/l.

The series of δ18O values is presented for all precipitation events in Moscow in 2014. Precipitation samples were taken at the observation site of the Meteorological Observatory of Lomonosov Moscow State University (MSU MO), and the isotopic analysis was carried out in the isotopic laboratory of the Department of Geography of MSU. The concentration of stable 18O in precipitation over Moscow in 2014 varied from -0.09 to -26.29‰. The maximum amplitudes of δ18O were registered in March-April and October. The pronounced interrelation was revealed between the oxygen isotopic composition of precipitation and surface air temperature (the correlation coefficient is 0.85). The computation of back trajectories of air masses and the analysis of weather charts demonstrated that the most isotopically light precipitation is typical of relatively cold air masses slowly moving over the continent during the last five days before precipitation. In this case, the ongoing condensation leads to the progressive isotopic depletion of precipitation (more and more isotope-depleted precipitation is registered). On the contrary, fast air transport from the middle and even from high latitudes of the Atlantic Ocean leads to the relatively constant of δ18O values of precipitation.

Based on atmospheric precipitation monitoring data for Moscow, we have revealed a number of episodes when the content of hydrocarbonates repeatedly surpasses the equilibrium level. These facts are associated with the complex structure of precipitation, which is caused by differences in the chemical composition of condensation nuclei. As a result, the underlying surface involves two groups of drops with acidities of different nature. The acidity of the first (“metal”) group is determined by the carbonate equilibrium with atmospheric CO2 and dissolved carbonates of alkaline and alkaline earth metals. The acidity of the second (“ammonium”) group is characterized by the balance between ammonia absorbed from the air and atmospheric acids. Because of this, the precipitation acidity measured during the monitoring is regulated not only in the air but also in the condensate collector. The mixing of the metal and ammonium groups of precipitation is accompanied by only a partial conversion of hydrocarbonates into dissolved CO2. Its termination is hindered when CO2 actually ceases to enter the atmosphere due to mass-exchange deceleration. As a result, the content of hydrocarbonates in the collector exceeds the equilibrium level. Some estimates indicate that the acidity of the ammonia component of precipitation can be much higher than the acidity according to monitoring data. This should be taken into account in estimating the health and environmental impacts. The true level of acid rain hazard can be estimated only by measuring the acidity of individual drops, whereas the results obtained with modern tools of monitoring can underestimate this hazard.

This paper reports a study of the April 2010 Eyjafjallajökull eruption on the atmosphere composition in Moscow. Concentrations of some gases, including sulfur dioxide, were measured at a station operated by Moscow University and the Institute of Atmospheric Physics. The impact of this eruption was felt, not only in the composition of the gaseous medium, but also in that of atmospheric precipitation as sampled and analyzed at the Meteorological Observatory of Moscow University. The NOAA hysplit model was used to carry out forward and backward trajectory analyses. It is shown that the descent of air masses during an anticyclone is a necessary condition for reliable recording of volcanic admixtures by ground-based stations.

Monitoring data and analysis of the variation in acidity and mineral composition of atmospheric precipitation in Moscow in 2012 are presented. We have found that the chloride anions in the precipitation are largely caused by chlorides of deicing salts. Here, the chloride anions, along with metal chlorides (components of deicing salts), are partly caused by dissolved hydrogen chloride. The appearance of hydrogen chloride in the atmosphere of Moscow has been shown to result from heterophase chemical reactions involving deicing salts. We have obtained preliminary estimates for the scales of the effect of these salts on the mineral composition and acidity of precipitations in Moscow.

Analyzed are the results of meteorological and environmental measurements performed over the 60-year period (1954–2013) at the Meteorological Observatory of Lomonosov Moscow State University. The significant positive temperature trend (0.04°C/year for 1954–2013) was obtained; it increased up to 0.07°C/year in 1976–2012. Considered are the features of seasonal variations of different atmospheric characteristics. Discussed are the type and causes of low-frequency changes in meteorological parameters, radiation balance components, radiation in different spectral ranges, and chemical composition of precipitation. Demonstrated are possible mechanisms of the more significant increase observed in air temperature in Moscow as compared with that in Central Federal District and their connection with the greenhouse effect in the urban atmosphere.

Анализируются результаты измерений метеорологических и экологических величин за 60 лет (1954-2013 гг.), выполненных в Метеорологической обсерватории МГУ им. М. В. Ломоносова. Получен значимый положительный тренд температуры (0,04°С/год за период 1954-2013 гг.), который в 1976-2012 гг. увеличился до 0,07°С/год. Рассматриваются особенности сезонного хода разных характеристик атмосферы. Обсуждаются характер и причины низкочастотных колебаний метеорологических величин, составляющих радиационного баланса, радиации в разных спектральных диапазонах, а также химического состава атмосферных осадков. Показаны возможные механизмы наблюдаемого более значительного увеличения температуры воздуха в Москве по сравнению с Центральным федеральным округом и их связь с парниковым эффектом в городской атмосфере.

Spatial variability of acidity and chemical composition of precipitation within theMoscowcity and theMoscowregion is analyzed basing on the results of the experiment carried out during summer 2013. The results were compared with the reference data from the MSU Meteorological Observatory where practically each precipitation event during more than 30 years was sampled and analyzed (ion composition and acidity). The synoptic processes were described and the technique of reverse trajectories of particles was applied. It was demonstrated that a little bit higher pH values are typical for the eastern part of theMoscowregion. Acid rains could occur both in the centre of the city and in the clean remote areas. The general composition of ions in theMoscowregion is characterized by predominance of Ca cations in combination with various anions, i.e. hydrogen carbonates, chlorides and sulfates. Unlike this, for already about 10 years the chlorides are predominant anions in precipitation sampled at the MSU Meteorological Observatory. The ratio of main ions is spatially more stable than the mineralization and the pH values. Generally rather diverse pattern of distribution of mineralization and pH values, particularly within the megapolis area is most probably an indicator of prevailing influence of local sources on the precipitation pollution.