About the Annual Course of Moscow Heat Island and the Impact on It of the Quarantine Measures to Prevent the COVID-19 Pandemic in 2020

Abstract

Seasonal differences in the Moscow urban heat-island intensity (UHII) have been studied in detail based on data obtained in 2018–2020 by the meteorological network of stations located in Moscow and Moscow region. It is shown that the annual cycle of this phenomenon is slightly pronounced. In most cases, the UHI is manifested stronger in summer and weaker in winter; however, in some months, the situation may be reverse. The question of the statistical significance of seasonal differences remains open. The closest statistical relationship was revealed between the UHI and lower clouds during the night hours, so that its highest intensity is observed in the least cloudy seasons (usually in summer). The UHII distribution functions are close to the normal law in summer and spring, and, in winter and fall, they are characterized by a noticeable positive asymmetry, because their values decrease and the mode approaches the lower physical limit. The period of strict quarantine restrictions during the COVID-19 pandemic in the spring and early summer of 2020 led to a rapid and statistically significant decrease in the Moscow UHII, probably due to both natural factors (increased cloudiness) and human activities (rapidly decreased anthropogenic heat fluxes and a weakened urban industrial haze creating an additional counterradiation).

Surface Urban Heat Island In Moscow During The COID-19 Pandemic Lockdown In 2020

“…2). This result is unexpected, since the UHI in the surface air layer of Moscow during the lockdown was much weaker than in the same period in two previous years (Lokoshchenko and Alekseeva 2022). In fact, in 2018 and 2019 the SUHI as well as the UHI was stronger than in 2020 during the lockdown (as one can see in Fig.…”

“…However, a reduction of anthropogenic heat sources during the lockdown is another factor, which, probably, also influenced on the SUHI intensity. Firstly, the contribution of reduced human activity to the weakening of the UHI in the surface air layer in Moscow at that time was shown in (Lokoshchenko and Alekseeva 2022). Evidently, both phenomena (UHI and SUHI) are related to each other.…”

“…To test its reliability, we can use the data about T on weather stations. During the COVID-19 strict lockdown the maximum space UHI intensity as a difference between Moscow centre (Balchug station) and rural zone outside the city (on average of 13 rural weather stations) averaged 1.46 ºC per day over 71 days (Lokoshchenko and Alekseeva 2022). Separate calculation of the same parameter only at noon (the closest reading of T to Aqua and Terra flights) during 71 days showed the value of 0.60 ºC.…”

“…However, it should also be noted that specific weather conditions (calm and frequent inversions in anticyclones) lead to an increase in air pollution even during quarantine (Ginzburg et al 2020). Among other things, the influence of the pandemic also led to the weakening of urban heat islands (UHI) in the surface air layer, e.g., in Moscow, according to Lokoshchenko and Alekseeva (2022). Possible reasons for this effect are the decrease of direct anthropogenic heat emissions and changes in the radiation balance in cities (weakening or disappearance of urban industrial haze, etc.…”