An analysis of the changes in the carbon monoxide (CO) and particulate matter (PM10) mass concentrations in the atmosphere near highways and residential areas over Moscow during the spring lockdown in 2020 against of the mass concentrations in the previous years (2015-2019) is presented. In the lockdown period, a decrease in the CO mass concentrations was about 40% near highways and only 10% in residential areas. A decrease in the PM10 mass concentrations by about 10% was found during that period. The closeness of lockdown effects in Moscow and other megacities is shown by the comparison of trends in the traffic intensity and pollutant mass concentrations. The special importance of motor vehicles as a source of carbon monoxide emissions in the analyzed megacities is demonstrated.

The combination of the parameters of temperature, humidity, and wind conditions of surface air, solar radiation fluxes, human metabolism under various modes of physical exertion and clothing properties characterize the thermal comfort. Under conditions of global warming, the climate characteristics that affect the quality of life, health, and well-being of people, in particular, the length of thermal comfort periods, are changing. Bioclimatic indices that determine the thermal comfort conditions depend not only on temperature changes, but also on humidity and wind speed trends. When comparing the results of the calculations of the thermal comfort period length with the use of air temperature observations and major bioclimatic indices, the authors have revealed a significant difference in the effect of changes in average wind speed on the length of the thermal comfort period in different regions of European Russia.

In the 1980s, one of the fundamental topics of scientific debate was the discussion of the global consequences of nuclear war. At that time, the hypothesis of “nuclear winter” emerged, in which scientists attempted to analyse the theoretical possibility of a sharp cooling of the Earth after mass fires, and to find natural analogues of a potential climatic catastrophe. In the following decades, the “nuclear winter” hypothesis went through various stages of criticism and reassessment. In the early 2000s, studies of the problem became regional in nature, focusing mainly on the possible consequences of local nuclear conflicts. In this article, the authors analyse the stages of development of research on the “nuclear winter” hypothesis, focusing on the Russian and American approaches, and conclude that the body of work produced by American and Soviet scientists in 1983–1985 represents the first attempts by the scientific community to conceptualise the problem of responsible nuclear policy.

Predictive estimates of changes in the climatological boundary of the permafrost zone as a function of the average annual air temperature in the Bolshezemelskaya tundra under various global economy scenarios until the middle of the XXI century have been obtained. The permafrost climatological boundary shift in the northeasterly direction observed in the period from 1950 to 2010 was determined from the threshold average annual air temperature. According to the adjusted scenario forecasts obtained using the climate model, it will continue in the coming decades under any global economy scenario and is an inevitable consequence of the anthropogenic influence on the climate. The study results are important for assessing the prospects and development of a long-term observation network created to monitor the permafrost state and greenhouse gas fluxes in the Russian Federation.

Estimates of the anthropogenic heat flux (AHF) created by megacities of the Russian Federation during the heating season have been obtained. To calculate the AHF value, two-dimensional models are created taking into account the height of the number of stories and the type of buildings for sixteen cities with a population of at least one million people. The source data is from the OpenStreetMap (OSM) open web mapping platform and the Yandex Maps website. Two algorithms for calculating AHF are considered, using building codes, thermophysical properties of enclosing structures, and the difference between internal and external air temperatures. The first algorithm uses the basic value of the required heat transfer resistance of the building envelope and the second uses the calculated value of the specific characteristics of thermal energy consumption for heating and ventilation of a building. AHF is assessed from the territory of the city within the administrative boundaries and from the urbanized territory, which is determined by multistory buildings. AHF density spatial distribution maps are provided for the four largest megacities—Moscow, St. Petersburg, Novosibirsk, and Yekaterinburg.

The paper deals with studying the influence of air pressure fluctuations on the health of patients. Since August 2008, the Obukhov Institute of Atmospheric Physics of Russian Academy of Sciences and the Central Clinical Hospital of the Russian Academy of Sciences (CCH RAS) observed air pressure fluctuations with a simultaneous registration of patients who were urgently hospitalized to the CCH RAS and classified as weather-sensitive. Weather-sensitive patients included patients diagnosed with myocardial infarction, angina, hypertension, extrasystole, stroke, and cerebrovascular disease. The data on 6078 patients over a four-year period (January 1, 2009-November 31, 2012) were processed. The results have shown an increase in the cases of patients' hospitalization with an enhancement of the external effects of air pressure.

Estimates of the anthropogenic heat flux (AHF) generated by megacities of the Russian Federation during the heating period are obtained. To calculate the AHF value, two-dimensional models were created taking into account the height, number of floors and the type of buildings for sixteen cities with a population of at least one million people. The source data is obtained from the OpenStreetMap open web mapping platform and the Yandex Maps website. Two algorithms for calculating AHF using building codes, thermophysical properties of enclosing structures and the difference between internal and external air temperatures are considered. The first algorithm uses the basic value of the required heat transfer resistance of the enclosing structure, the second – the calculated value of the specific characteristic of the consumption of thermal energy for heating and ventilation of the building. The AHF is assessed from the territory of the city within the administrative boundaries and from the urbanized territory, which is defined by multi-store buildings. Maps of the spatial distribution of AHF density are provided for the four largest megacities: Moscow, St. Petersburg, Novosibirsk and Yekaterinburg.

This article analyzes the results of measuring the oxygen content in Moscow in 2017–2021 at three Budgetary Environmental Protection Institution Mosecomonitoring automatic stations for monitoring atmospheric pollution. Seasonal variations in oxygen content in the city are considered, the issues of compliance of the values with the scale of comfort level for human breathing developed by medical specialists are discussed, and measurement data are compared with the results of calculating the oxygen concentration in the air by the magnitude of meteorological parameters. According to the measurements, diurnal variations of the O2 content in the surface urban air, more pronounced in the warm season, are revealed for the first time. The minimum O2 content is observed in summer in the early morning hours. The main natural and anthropogenic processes that determine the variability of oxygen content in the surface air of a megalopolis at different time scales are discussed.

In light of observed and projected climate changes, it is necessary to develop science-based methods and criteria to assess the need for preventive adaptation to the consequences of climate change and associated risks. The nature, the population, and the economy always respond to changing conditions, including climate changes, and adapt to them. However, the speed and effectiveness of such reactive adaptation may be insufficient. For this reason, planning adaptation measures and implementing preventive adaptation have become critical for the sustainable development of the economy, improving the quality of life of people, and preserving ecosystems. This paper proposes an approach to identifying the quantitative indicators of climate impact that show the need for preventive adaptation when they exceed threshold values. This approach can also be used in the development and implementation of adaptation plans for the sectors of the economy and the subjects of the Russian Federation.

The variability of surface methane (СН4) concentration in Moscow at different time scales is analyzed using long-term regular measurements from the State Environmental Institution Mosecomonitoring (2005–2020). Possible mechanisms that form the methane-concentration field in the city’s atmosphere are discussed. The average concentration of methane in the urban surface layer during the cold half of the year is lower, the higher the average air temperature of the previous warm half-year. The lowest methane concentrations in Moscow in 2010 and 2011 are associated with the hot summer of 2010, which was accompanied by severe wildfires and partial dry-out of wetlands in central European Russia. The intra-annual variations in СН4 concentration exhibit minima in summer and maxima in winter. An additional maximum concentration in August–September is typical only of the night methane concentrations. In the diurnal cycle, there is a higher methane concentration in the air at night than during the day. The results demonstrate the complexity of multidirectional natural processes in the atmosphere and at the underlying surface that form a dynamically changing field of methane concentration in the surface air of a megacity.

The anthropogenic heat flux associated with energy consumption for heating buildings has a significant impact on the heat balance of urbanized areas and the intensity of the urban heat island. The energy consumption of the urban economy is highly dependent on meteorological conditions, as well as on their annual and daily trend and variations. This is especially true for the part of energy consumption that is spent on maintaining a comfortable indoor temperature. This article uses the OpenStreetMap open web mapping platform which allows one to make an inventory of anthropogenic heat fluxes by the difference between internal and external air temperatures and based on building codes and thermophysical properties of enclosing structures. A simple nonstationary energy balance model of the interaction of the urban boundary layer of the atmosphere with the urban canopy layer (UCL) containing anthropogenic heat sources is formulated.

Mathematical models of the atmosphere have been developed for a laser wavelength of 0.532 μm, including the optical characteristics of a crystalline environment for aggregate structures of ice particles. Calculations of the optical radiation transfer from subnanosecond laser pulses of ground stations to high-orbit and low-orbit spacecraft in the presence of clouds of upper and middle tiers are performed. It is shown that the principles of no-demand (one-way) laser ranging can be implemented in the presence of frontal cirrus, cirrostratus, and cirrocumulus clouds, as well as altostratus clouds in the sky with established limitations on optical thickness.

This is the introductory article for the special issue of Izvestia, Atmospheric and Oceanic Physics dedicated to the 2019 Lomonosov Gold Medal of the Russian Academy of Sciences awarded to Academician Georgy Golitsyn “for making an outstanding contribution to the study of atmospheric physics of the Earth and planets and the development of the theory of climate and its changes” and to foreign member of the Russian Academy of Sciences Professor Paul Joseph Crutzen “for making an outstanding contribution to the chemistry of the atmosphere and assessing the role and biogeochemical cycles in climate formation.” This issue includes an article highlighting the contributions Golitsyn and Crutzen made to the study of physics and chemistry of the atmosphere, climate, and biogeochemical cycles, as well as articles written for this special issue with the participation or recommendation of the laureates.

It is well known that large cities and urban agglomerations not only make a decisive contribution to the growth of greenhouse gases in the atmosphere, but also significantly shape their own climate by transforming the underlying surface of urban areas, as well as thermal, gas and aerosol pollution of the urban boundary layer of the atmosphere. The most powerful manifestation of the city’s influence on local and regional climate processes is the thermal pollution of the atmosphere created by anthropogenic heat fluxes forming primarily due to the energy consumption of the urban economy. This paper summarizes the results of the work of the authors on numerical modeling of the influence of anthropogenic heat fluxes (thermal pollution of the urban atmosphere) on the climatic characteristics of urban agglomerations using the COSMO-CLM mesoscale climate model. The work was carried out as part of the Analysis of an impact of the regional climate change on the residential and commercial energy consumption of Russian megacities project of the Russian Science Foundation.

The intensity of an urban heat island depends on the location, layout and development of the city, the number and density of its population, and the energy consumption of the urban economy. These dependencies can vary greatly from city to city. In recent years, more and more attention has been paid to the dependence of the city's climate characteristics on global and regional climate processes, their trends and variations. At present, there is no clear answer to the question of how climate changes affect the evolution of an urban specific city, since modern climate changes in different cases can both increase and decrease the intensity of the urban heat island. This work discusses the reasons some stabilization of the intensity of the Moscow heat island, observed in the second half of the XX century and early XXI century, and the relationship of this phenomenon with the weakening of continentality climate in the Moscow region.

The results of an analysis of changes in the atmospheric air quality in Moscow during the lockdown period and the decline in business activity caused by the COVID-19 coronavirus pandemic are presented. The observed changes in urban air pollution represent a unique experiment to assess the impact of various anthropogenic influences on the composition of atmospheric air. The influence of weather factors and transport activity on the level of pollution in the spring of 2020 is considered. The level of the main pollutants in the atmosphere decreased by 30–50% during the period of lockdown, and a different type of changes was revealed near highways and in residential areas. This article discusses the possibilities and difficulties of using a "unique experiment" on a sharp decrease in traffic intensity in large cities to determine the contribution of various branches of the urban economy (transport, energy, industry, waste processing) to the total air pollution in large cities.