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Abstract This study analyses the departure of the velocity-variances profiles from their quasi-steady state described by the mixed-layer similarity, using large-eddy simulations with different prescribed shapes and time scales of the surface kinematic heat flux decay. Within the descriptive frames where the time is tracked solely by the forcing time scale (either constant or time-dependent) describing the surface heat flux decay, we find that the normalized velocity-variances profiles from different runs do not collapse while they depart from mixed-layer similarity. As the mixed-layer similarity relies on the assumption that the free-convective boundary layer is in a quasi-equilibrium, we consider the ratios of the forcing time scales to the convective eddy-turnover time scale. We find that the normalized velocity-variances profiles collapse in the only case where the ratio ($$\widetilde{r}$$ $\tilde{r}$) of the time-dependent forcing time scale to the convective eddy-turnover time scale is used for tracking the time, supporting the independence of the departure from the characteristics of the surface heat flux decay. As a consequence of this result, the knowledge of$$\widetilde{r}$$ $\tilde{r}$is sufficient to predict the departure of the velocity variances from their quasi-steady state, irrespective of the shape of the surface heat flux decay. This study highlights the importance of considering both the time-dependent forcing time scale and the convective eddy-turnover time scale for evaluating the response of the free-convective boundary layer to the surface heat flux decay. 

On example of the city of Nadym, located in the Yamalo-Nenets Autonomous Area, the authors consider the socio-ecological problems of the development of green, blue and white open urban spaces. The research approach presented in the article is based on the study of a multifaceted complex of urban social and natural systems in their integrated unity, not just as public places, but as biomes — highly integrated urban ecosystems. A posteriori the researchers based on the materials of interviews conducted in 2020 with experts who in different years took part in the study or planned the development of the open urban spaces in Nadym, as well as on the analysis of available publications on this topic and publicly available data. The study found that factors such as the short summer, during which many residents leave the city, as well as the prevalence of freezing temperatures for almost eight months, in fact, transform the green and blue spaces of Nadym into white. This situation indicates the advisability of a more active appeal to the concept of a “winter city” in the development of the city urban environment. The application of the concept principles can be in demand in the process of creating more comfortable living conditions and spatial mobility of the Nadym residents, as well as for developing the recreational opportunities of the city open spaces and integrating them into the natural environment surrounding the city, which in general can be considered as one of the factors for the sustainable development of the city and the formation of post-industrial features in its socio-economic life.