The long-term dynamics of both urban heat island (UHI) and urban dry island (UDI) intensities over the city of Moscow, Russia, has been analyzed for the period from the end of the nineteenth century until recent years using data of the ground meteorological network. Besides traditional maximum heat/dry island intensity, an additional parameter—station-averaged intensity as a mean difference between the data of all urban and rural stations—has been used. The traditional maximum (mean annual) UHI intensity in Moscow was nearly 1.0°C at the end of the nineteenth century, 1.2°C one century ago, 1.5°–1.6°C both in the middle and at the end of the twentieth century, and 2.0°C in recent years. The station-averaged UHI intensity was equal to 0.7°–0.8°C in the second half of the twentieth century and increased up to 1.0°C in recent years. It is probable that stabilization of both parameters from the 1950s to the 1990s was connected with the extensive city growth at that time (mass resettlement of inhabitants from the overpopulated city center to the new urban periphery since the 1960s). The new increase of UHI intensities is the result of the new intensive city growth. The relative humidity in Moscow significantly decreased during the last 146 years (mostly because of warming), unlike water vapor pressure. The UDI is closely connected with the UHI; the absolute value (modulus) of its intensity is increasing in time from −4% at the end of the nineteenth century to −9% now. During the last two decades, the UDI as well as the UHI became much stronger than before.

The urban heat island (UHI) intensity in Moscow and the influence of various meteorological parameters are discussed using weather station data. The maximal and average in-space UHI intensities, i.e., a comparison of air temperature T either in the city centre or in the whole urban area together with rural zone have averaged 1.9 and 0.9 °C, respectively, in recent years. The UHI in Moscow has stabilized over the past decade and is not growing. Under conditions of a strong anticyclone, the maximal UHI intensity in space and time reaches 11–12 °C. Low cloudiness and amplitudes of diurnal air temperature, as well as surface temperature, demonstrate the closest relationship with the UHI intensity among other parameters with the correlation coefficient of up to −0.67 for low cloudiness and the maximal UHI intensity. The effect of wind speed, total cloudiness and relative humidity on the UHI is slightly weaker, but still significant. The relationships of all meteorological parameters with the maximal UHI intensity are closer than those with the average one. The multiple correlation coefficient between the maximal UHI intensity and both parameters (low cloudiness and average daily wind speed) is 0.76–0.82. The UHI intensity function of air temperature has a minimum in the range from −4 to 0 °C; its growth both at lower and higher T is due to the influence of anticyclonic weather. The UHI intensity function of wind speed decreases with wind strength. The threshold value at which this function asymptotically approaches its lower limit is 10 m/s in the 40–200 m air layer. The UHI intensity functions of both total and low cloudiness decrease with increasing cloudiness and the differences between them are significant if the cloud cover is more than 50%.

The experimental data about thermal stratification of a low layer of atmosphere, received by the sodar sounding and direct measurements simultaneously, are summarized and discussed. The conclusion was made that sodar records of small-scale turbulent structures can be efficiently explained in terms of a thermal stratification type. The statistics of the thermal stratification in the lowest 800-m air layer are presented by the data of long-term sodar observations during 10 years at Moscow University, which were analyzed separately per hour. According to these data, the climatology of inversions, thermal convection, and weak-stable stratification is described. The mixing layer height, estimated by margins of turbulent structures on sodar records, was analyzed and compared with the one derived by traditional Holzworth method using radiosonde measurements. Climatology of the mixing-layer height in Moscow by the sodar data, as well as its variations due to synoptic effects, is discussed. A new approach is the usage of integral parameters (e.g., the instability energy) instead of heights to determine the potential mixing more precisely. This method allows us to eliminate errors of the height determination, when the temperature profile and dry-adiabatic line are close to each other. Moreover, instability energy in any case represents more realistic estimations of mixing because inertial lifting was taken into account.

The results of the 2002–2012 continuous once-a-minute measurements of the composition of the surface air over Moscow, which were taken at the joint ecological station of the Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, and the Geographic Faculty of Moscow State University, are discussed. It is shown that the annual increase (on the order of 1%) in the content of surface ozone is stable and the decrease in the content of nitric oxide is statistically significant, while the content of nitric dioxide remains almost unchanged. Reliable regularities in both diurnal and annual variations in the contents of the five trace gases O₃, NO, NO₂, CO, and SO₂ have been studied in detail. Statistical relations of the content of sulfur dioxide with the amount of reserve fuel (black oil) used in city heating (this relation is the strongest one), wind velocity in an atmospheric layer up to a height of 200 m, and air temperature have been analyzed. The influence that wind velocity has on the surface contents of trace gases and carbon dioxide has been studied for the first time on the basis of long-term ‘MODOS’ sodar data. It is shown that, with an increase in wind velocity, the contents of nitric and carbon oxides generally decrease, the content of ozone increases, and the content of sulfur dioxide decreases starting from an intermediate value of 1–2 m/s due to the prevalence of high sources of this gas. An additional maximum found in the content of carbon dioxide at high wind velocities may be associated with the long-range transport of CO₂.

Thermal stratification of the lower 800-m air layer over Moscow, including distribution functions of inversion heights and duration, has been studied in detail based on ECHO-1 sodar data. The distribution of the bottom height of elevated inversions, unlike the thickness of surface inversions, is bimodal, which reflects the diversity of their origin. The lifetime of morning elevated inversions (remains of night surface inversions) is, on average, ~3 h, and, in some cases, over 6 h; their bottom heights usually do not exceed 350 m. Superlong elevated subsidence inversions are more often observed in Moscow from November to February and may be detected on sodar records continuously up to 120 h. The influence of retentive inversion layers on the surface content of trace gases in the atmosphere over Moscow has been studied based on the 2002–2016 data. The final destruction of morning elevated inversions results in a rapid acceleration of increase in the content of O₃ and a start of decrease in the content of NO₂ in the atmospheric surface layer. Both effects reflect the intensification of a vertical turbulent exchange. Such a rapid increase in the rate of growth of ozone after the inversion destruction is not associated with its photochemical generation and is apparently the result of dynamic processes (increased downward ozone fluxes from upper air layers). In contrast, under the conditions of long-lived elevated subsidence inversions in fall and winter, no statistically significant variations in the surface contents of five trace gases (O₃, NO, NO₂, CO, and SO₂) have been found.