ИСТИНА

The dynamics of the urban ‘heat island’ of Moscow city in time is discussed. As it shown its intensity since 1880s till recent years increased twice, i.e. became more from 1.0-1.2 to 2.0 ºC. One more additional parameter – so-called ‘areal’ UHI intensity – is suggested. It represents a value averaged both in time and in space (a difference between mean air temperature in the city area and outside the city). The maximal ‘heat island’ intensity in Moscow may reach up to 14 ºC, usually at night or in the early morning in anticyclone conditions. Weekly course of the air temperature T in Moscow is closely connected with the urban ‘heat island’ phenomenon. In average of last 50 years a gradual increase of T during week-days and sharp decrease (cooling) on weekends has been detected in Moscow. The difference between T at the end of working week and on Sunday or Monday is equal to nearly +0.25 ºC in average of a year; +0.35 ºC in cold season (from November to March) and +0.45 ºC at night (at 03 a.m.) in cold season. This difference may be explained by industrial haze and plumes from smoke stacks which are gradually accumulated from Monday to Friday and reduces effective nocturnal radiation in the city, especially during winter nights.