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CLOUD SEEDING OPERATIONS TO MODIFY WEATHER CONDITIONS OVER
CITIES: 2003-2006

Koloskov, B.P. (1)., Korneev V.P. (1)., Petrov V.V.(1), Beryulev G.P.(2), Danelyan B.G.(2), Chernikov A.A.(2) ,
Shchukin G.G.(3)
(1)
Agency of Atmospheric Technologies (Agency ATTEX, ROSHYDROMET)
Novovagankovsky per. 8, Moscow, 123242, RUSSIA
Tel: +7(095)255-2372; Fax: +7(095)255-2134; e-mail: attech@mail.ru
(2)
Central Aerological Observatory (CAO)
Pervomayskaya 3, Dolgoprudny, Moscow Region, 141700, RUSSIA
(3)
Research Center for Atmospheric Remote Sensing,
St. Petersburg, Russia

Abstract
Some results of activities on cloud seeding operations to modify weather conditions over Moscow
and St.Petersburg (Russia) conducted during 2003-2006 are presented. 18 operational works on
improvement of weather conditions were executed during this period. The main purpose of these works
was the dissipation of clouds and reduction or stopping of precipitations over the protected cities during
the large social, sporting or other special events.
Four basic concepts of cloud dissipation and precipitation redistribution were applied to improve the
weather conditions depending on a weather conditions, type of clouds and intensity of precipitation
processes: 1) dispersion of stratiform clouds; 2) destruction of convective clouds by a dynamic method;
3) premature rainfall initiation windward of the city with the purpose of the formation of a “rain shadow”
(i.e. reduced rain) and 4) intensive seeding of the rain-producing cloud layers with the purpose of
“overseeding”.
Up to 12 aircraft, such as Il-18, Аn-12, An-72, An-30, Аn-26, An-28, An-32 and M-101 “Gzhel”,
specially equipped with the meteorological equipment, data acquisition systems, “Land – Aircraft – Land”
data transmission system and means for cloud seeding have been prepared for fulfillment of the works.
Liquid nitrogen, granulated carbonic acid (“dry” ice), meteorological silver iodide cartridges and
packages with coarse-dispersion powder were used as reagents for seeding of clouds. Management of
works and the control of results were carried out with the help of the automated radar systems MRL-5 –
AKSOPRI in Moscow and MRL-5 – MERCOM in St.Petersburg.

1. Introduction et al. 1996, Korneev et al. 2003/. The main
purpose of these activities was the dissipation of
In weather modification research in Russia,
clouds and reduction or stopping of precipitations
special attention was given to the development of
over the protected cities.
methods and technical means for dissipating
clouds of some forms and preventing or 2. Main cloud seeding concepts
substantially reducing precipitation amount. The
Four basic concepts of cloud dissipation and
practical objectives were to change radiation
precipitation redistribution are generally used
balance and to increase the income of solar
depending on a weather conditions, type of clouds
radiation, to reduce municipal expenses for snow
and intensity of precipitation processes:
removal and clearing the roads and streets in large
1. Dissipation of cold stratiform clouds.
cities, to create favorable meteorological conditions
2. Prevention or reduction of the intensity of
for carrying out social programs, sporting
shower rains and thunderstorms by a dynamic
competitions or some other situations when the
technique.
necessity may arise to reduce the rainfall. The first
3. Premature rainfall initiation from cloud
experiment on practical application of these
systems windward side of the target area with the
opportunities was carried out during eliminating the
purpose of formation of a “rain shadow”, i.e.
consequences of Chernobyl disaster in 1986
reduction of precipitation over the given site.
/Beriulev et al. 1990/. Since 1995 the organizations
4. Reduction of rainfall intensity over the given
of ROSHYDROMET conducted more than 30
site by intensive seeding the rain-producing cloud
works on improvement of weather conditions in
layers moving toward it, aimed at weakening the
areas of the large cities – Moscow and
mechanism of precipitation generation through the
St.Petersburg (Russia), Tashkent (Uzbekistan),
“overseeding” of clouds, i.e. creating excessive
Astana (Kazakstan) /Bedritsky et al. 1996, Belyaev
concentrations of ice crystals.

All these methods are based on the unstable same as the distance of a half-hour or one-hour
state of atmospheric processes. Of the various wind transport of clouds.
types of instability, those with most potential for
local modification of precipitation and cloud- 3. Technical means
formation processes are the phase stage of cloud
water (existence of supercooled liquid water) and The described methods were realized using
the convective instability of the atmosphere. specially instrumented aircraft of different types. In
The feature that the first and the last two complementation to the Velocity of ascent types,
concepts have in common is the use of ice- used in 1995 – 2002 (Il-18, An-12, An-30, An-26
producing agents and An-72), three new types of aircraft – An-28,
The first concept was to dissipate stratiform An-32 and M-101T "Gzhel" were used in weather
clouds or to reduce precipitation falling from them modification activities in 2003 – 2006.
over the target site. Studies have shown that in An-32 aircraft (Fig. 1) differs from An-26
certain conditions seeding of stratiform clouds with aircraft, used in works to modify weather conditions
an ice-forming agent (“dry ice” or liquefied over cities, of the greater velocity of ascent and the
nitrogen) and aerosols (silver iodide) either leads greater carrying capacity, and also higher practical
to their dispersal or enhances precipitation from ceiling of flight (more than 9000 m).
them over a certain period, followed by a further
relative reduction of the intensity and amount of
precipitation (“rain shadow”). Thus, by causing a
relative increase in precipitation at an appropriate
distance windward from the target area it is
possible to ensure that the dispersal or “rain
shadow” zones are located over it.
The second concept was to suppress the
development of convective clouds using coarse
powders. The methods to destroy developing
convective clouds, using artificially generated
downdrafts, were theoretically justified and Figure 1. Aircraft Аn-32
thoroughly tested under laboratory and field
conditions /Petrov 1986, Belyaev et al. 1987/. It is For carrying out of cloud seeding operations
based on artificial initiation of downdrafts in the Аn-32 aircraft was equipped by: the device for
convective clouds by releasing powdered agents dropping the packages with coarse-dispersion
into their tops. As was shown in CAO experiments powders, means for cloud seeding using dry ice
/Belyaev et al. 1987/, this method has proved and liquid nitrogen generator GMCHL-A.
sufficiently effective – up to 90% for single-cell The aircraft of the middle class, Ан-28 (Fig. 2),
isolated air-mass clouds, and 60-65% for frontal as well as Ан-32, for the first time has been used in
clouds. works to modify weather conditions over cities in
The other two methods (third and fourth 2006.
concepts) use weather modification techniques
similar to that employed in the first method aimed
at the dissipation of clouds.
In both cases it is possible to estimate the
distance of advance seeding relative to the
protected territory so as to prevent undesirable
clouds and precipitation from reaching it.
The fourth concept of cloud modification aimed
at reducing precipitation over target area consist in
seeding rain-producing cloud systems on the
windward side of protected territory with above-
normal quantities of ice-forming agent.
Overseeding, i.e. producing ice crystals inside Figure 2. Aircraft Аn-28
clouds in concentrations many times those of
naturally generated ice, brings about a situation an The charge of fuel of An-28 aircraft is 350
abrupt increase of the number of simultaneously kg/hour. The weight of useful loading of the plane
growing precipitation particles is accompanied by a makes 1800 kg that has allowed simultaneously
marked slowdown in their growth and a reduction with four members of crew, to place onboard of the
of their falling speed. This, in turn, leads to plane a nitrogen generator and 20 packages with
noticeable temporary reduction of precipitation. In coarse-dispersion powders.
cloud overseeding operations, the distance of Aircraft M-101T "Gzhel" (Fig. 3) is intended for
seeding paths from the borders of the protected performance of works on cloud seeding. This
territory is chosen so as to be approximately the aircraft has the low charge of fuel (100 kg/hour).

with on-board kit of this system. In the control center
the Base kit of this system was installed (Fig. 6).

Figure 3. Aircraft M-101T "Gzhel"

The M-101T "Gzhel" aircraft is equipped with
easily removable onboard complex of the measuring
equipment and technical means for cloud seeding.
The means for seeding include the nitrogen
generator of ice particles (Fig. 4) and a system to
Figure 6. Data transmission system.
release 256 silver iodide pyrotechnic PV-26 flares
(Fig. 5). As an example, trajectories of airplanes
imposed on the radar-tracking image of the top
clouds are presented on Fig. 7.

Figure 4. The nitrogen generator of ice particles,
installed onboard of M-101T "Gzhel" aircraft

Figure 7. The trajectories of aircrafts imposed on the
radar-tracking image of the top cloads.
Management of works and the control of results
were carried out with the help of two wavelengths
MRL-5 meteorological radar, equipped with the
automated radar system AKSOPRI, installed in
Moscow (Krylatskoye) and the system MERCOM in
St. Petersburg.
4. Results of an improvement of weather
conditions
Figure 5. A system for shooting pyrotechnic PV-26 flares All the methods and technical aids described
above were employed successfully in the activities
associated with eliminating the consequences of
In 2004 information-measuring system, used for
Chernobyl disaster in 1986, and improving weather
weather modification activities, was complemented
condition in Moscow (in 1995-2002), Tashkent (in
by data transmission system “Land – Aircraft –Land”
1994-2002), and Astana (in 1998) /Korneev et al.,
/Petrov, et al., 2007/. This system allows to display
2003/. Some characteristics and results of an
the locations and flight paths of aircrafts on monitor
improvement of weather conditions in Moscow and
of the automated radar system, as well as send
St.Petersburg cities conducted during 2003-2006
aboard the aircrafts radar maps of distribution of
are presented in Table 1.
cloud and precipitation in region of works. Each
The seeding effect was monitored using the
aircraft participated in these activities was equipped
network of four automated radar systems MRL-5 –

AKSOPRI in Moscow area and radar system MRL-5 decrease of intensity and amount of precipitation
– MERCOM in St.Petersburg, and raingauge data. over the protected territories in comparison with rain
Analysis of these information showed that due to fallen upwind and in its nearest surroundings, thus
cloud seeding it was possible: 1) to attain the demonstrating the effectiveness of cloud seeding
destruction of stratiform and precipitating convective operations, conducted in Moscow and St.Petersburg
clouds, or 2) to obtain the considerable, 2-10 times during 2003-2006.

Table 1. Characteristics of cloud seeding operations on an improvement of weather conditions
over Moscow and St.Petersburg (Russia) conducted during 2003-2006.
Number Precipitation
of Number of flights,
Event Date duration of flights
aircrafts target area neighborhood
Day of the Victory (Moscow)
2003 9 May 10 aircraft 1 flight, 5 h 10 min no rain no rain
2004 9 May 10 aircraft 13 flights, 65 h 05 min to 1-2 mm to 4-5 mm
2005 7- 9 May 12 aircraft 35 flights, 214 h 08 min 7 – no rain 7 – to 0.2 mm
8 – to 0.2 mm 8 – to 2-3 mm
9 – no rain 9 – to 1-2 mm
2006 9 May 11 aircraft 14 flights, 80 h 39 min to 0.5-1 mm to 3-4 mm
Day of Russia (Moscow)
2003 12 June 10 aircraft 10 flights, 53 h 51 min no rain to 0.5-1 mm
2004 12 June 10 aircraft 1 flight, 8 h 30 min no rain no rain
2005 12 June 10 aircraft 14 flights, 80 h 56 min no rain to 0.3-0.5 mm
2006 12 June 7 aircraft 9 flights, 48 h 57 min to 0.3-0.5 mm to 2-3 mm
Day of Moscow city
2003 6-7 Sept 10 aircraft 11 flights, 64 h 33 min 6 – to 0.3 mm 6 – to 2-3 mm
7 – no rain 7 – no rain
2004 4-5 Sept 10 aircraft 5 flights, 31 h 38 min no rain no rain
2005 4 Sept 10 aircraft 6 flights, 49 h 06 min no rain no rain
2006 2 Sept 11 aircraft 6 flights, 26 h 07 min no rain to 0.2-0.3 mm
300th anniversary of 30-31 7 aircraft 18 flights, 91 h 57 min 30–to 0.5-1 mm 30 – to 2 mm
St.Petersburg, 2003 May 31– to 0.2 mm 31 – to 0.5 mm
The International tournament on
athletics “Moscow challenge”, 20 Sept 10 aircraft 4 flights, 21 h 42 min no rain to 0.5-1 mm
2003
The sixth Moscow festival of
beer, 2004 10 July 10 aircraft 1 flight, 5 h 00 min no rain no rain
Day of the Railwayman
(Moscow), 2006 6 Aug 8 aircraft 8 flights, 23 h 24 min no rain to 2 mm
“Scarlet sails” open air festival 23-24
(St.Petersburg), 2006 June 6 aircraft 6 flights, 45 h 14 min no rain to 5-10 mm
The Summit of “The big eight” 15 – no rain 15 – no rain
(St.Petersburg), 2006 15-17 11 aircraft 20 flights, 138 h 10 min 16 – to 4-5 mm 16– to 30-40 mm
July 17 – to 0.5 mm 17 – to 4-5 mm

Union Russian Conference, L., Hydrometeoizdat, 233-
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th
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