Illuminance Regime of Moscow under Smoke Haze Conditions

O. A. Shilovtseva

Considered are the conditions of the natural illuminance of Moscow during the period of smoke haze caused by forest and peat-bog fires in summer 1972, 2002, and 2010. Assessed is the impact of such extreme conditions on total, scattered, and direct illuminance. The main attention is paid to the illuminance attenuation due to the smoke haze in the case of few-cloud weather. It is demonstrated that if smoke aerosol is present, direct illuminance decreases by 70% on average and total illuminance, by 30% as compared with similar conditions on the days with typical aerosol. Small increase in scattered illuminance is observed (by 45–90%). The analysis of illuminance in the cases of the haze of various intensity demonstrated that in the case of very intensive smoke screening, direct illuminance decreased to zero, total illuminance, by 70%, and increase in scattered illuminance slowed down. On such days horizontal visibility was equal to 100–200 m like under the conditions of thick fog.