Due to the forecast of the difficult weather situation Moscow Authorities have decided to carry out work on meteoprotection of Moscow during the opening of the Festival «Spasskaya Tower» from 4pm to 12am hours of 01.09.2013. Upon request of the Government of Moscow Chief of the General Staff of the Defense Ministry instructed the Command of the Air Force to set up at the group of aircrafts An- 12 and An -26 ( 8 core and 2 spares) at «Chkalov» airport. Weather conditions in the Moscow region in the morning September 1, 2013 were determined by the vigorous occluded cyclone slowly moving within the day through the Moscow region from south to north. The atmosphere was stably stratified it was widely downpouring. In the city and suburbs there were a multi-layer laminated and layered rain clouds . Cloud base was located at an altitude of 100-150 m, the top of the clouds was higher than 6,000 m. Zero izotherme was at an altitude of 2800 m, tropopause was located at an altitude of 11 km . By 1pm the upper limit of the main precipitation layer dropped down to 3200 m, the rain turned into a protracted drizzle . In the lower and middle troposphere was weak erratic the northern and eastern winds (10-20 km / h ). The temperature at the ground did not exceed 14 ° C.
The start of aerial works on the effects on the area of cloudiness and precipitation impinging over Moscow was scheduled at 1pm. Depending on the actual weather situation all 8 aircrafts could be raised in the air with the interval of 10 min. However due to the difficalt meteo situation around «Chjalov» aerodrome (cloud base and horizontal visibility were less than the minimum allowed for takeoff ) only three aircrafts were raised in the air: Antonov An -12 (№ 68) — 1pm , An- 26 (№ 90373 ) — 1.24pm and the An -12 (№ 17) -2.57pm. At that moment the intensity of rainfall in the city was up to 2.3 mm / h and the top of the cloud reached a height of 5000-6000 m ( Fig. 1).
Aircrafts were producing effects on clouds at altitudes of 3,900 to 5,500 m in the north- eastern and north -western sectors at a distance of 5 to 100 km from Moscow. Once the supply of reagents has been exhausted aircraft landed : An- 26 (№ 90373 ) landed at 5.04pm, the An -12 (№ 68) — at 5.45pm . After refueling aircraft An -26 (№ 90373 ) went to the second flight at 6.56pm and instead of AN- 12 (№ 68) at 7.56pm was raised An- 12 (№ 12). The delays in aircraft departures were caused by the meteorological conditions at Chkalov aerodrome.
Rainfall in the city was observed up to 6.40pm ( Figure 2).
Works on the impact on 01.09.2013 were finished at 11.30pm .
( Fig. 1)
( Fig. 2)