The Blanket Effect is intended for others to learn about weather modification and its related subjects in an easy to understand way. Started in 2005, this blog is a work in progress as the technology advances

February 29, 2008

Iran Joins the Pack

(note: excerpted from PDF , corresponding map of Iran from


Beryulev G.P. Danelyan B.G., Koloskov, B.P.,
Semsar Yazdi A.A. and N. Pahlavanhosseiny
Central Aerological Observatory (CAO)
Pervomayskaya 3, Dolgoprudny, Moscow Region, 141700, RUSSIA
Agency of Atmospheric Technologies (Agency ATTEX, ROSHYDROMET)
Novovagankovsky per. 8, Moscow, 123242, RUSSIA
National Cloud Seeding Research Center (NACSER),
Yazd, IRAN, P.O.Box: 89195/611


The technology of cold cloud modification using ecologically innocuous materials, aimed at planned precipitation enhancement, is now becoming ever more popular as a means of solving the problems of freshwater deficiency.

In the Islamic Republic of Iran, as in many other countries, the cloud seeding is used to alleviate the water stresses.

To increase the storage water capacity of the Latian and Karaj dams located near Tehran, a Canadian weather-engineering company carried out the four-year cloud seeding project (1974-1978) sponsored by the Ministry of energy I.R. of Iran (Semsar Yaszdi, 2003).
(image left of Latian dam, from, image below right of Karaj dam, from

Thirty ground generators and one aircraft were used to inject silver iodide into clouds. As a result of seeding 13-15% enhancement of precipitation was reported (Semsar Yazdi, 2003; Noorian A.M., et al., 2003).

In 1988 the equipment of the mentioned project was transferred to [the] Yazd region and new cloud seeding project was carried out from 1989 to 1996 in Central part of Iran on the slopes of Shirkuh Mountains. These operations covered limited zones in 1990-91 and 1994-1996.
(image left: location of Yazd region, from

After establishing the National Cloud Seeding Research Center (NACSER) affiliated with the Ministry of Energy, the Central Aerological Observatory (CAO), Russia, jointly with Iranian specialists started in 1999 the long-term Operational Project on precipitation enhancement by cold cloud seeding over the Central Iran (the Yazd province and nearby areas) under an agreement with the government of Yazd Province.

Project activity in 1999-2001

The Central part of Iran is characterized by highly heterogeneous topography (height from 1000 to 4000 m above sea level) and high precipitation variability (from 50-60 mm per year in the center of the Yazd Province up to 300-400 mm in the west and south-west).
image right of
Shir Kuh mountain in central Iran, from

The season of precipitation in Yazd lasts 8 months (from October to May). Moreover, 90% of the annual amount fall out from December through May, and 67% during 4 months from January through April. During this period 2-5 days with precipitation are observed monthly. Thus, the wet season (December – April) is most appropriate for conducting works on precipitation enhancement.

The physical and statistical design of the Project in Iran is similar with the Syrian Project, fulfilled by the CAO jointly with Syrian specialists in 1991-1997.

The objective of the Iranian Project is to determine whether seeding of cold convective and stratiform clouds near their tops (temperature from -4oC to -21oC) with ejectable silver iodide flares and dispersing the liquid nitrogen would enhance precipitation over the Central plateau of Iran.
(image left explaining convective process, click for detail, from

The Operational Project on the precipitation enhancement by cold-cloud seeding over the Central Iran was started in 1999 by CAO (
Central Aerological Observatory) jointly with NACSER (National Cloud Seeding Research Center).

In 1999-2001 the Russian An-30, twin-engine, turboprop, seeding-research aircraft was employed in the Project.
(image right: example of An-30 plane, from

It was equipped with a measuring and data acquisition system for processing, recording and real-time on-board displaying basic navigational and flight parameters as well as the atmosphere and cloud characteristics, such as temperature, dew point, wind speed and direction, cloud liquid water content and icing intensity.

The aircraft was also equipped with: 1) cloud seeding means carrying 384 ejected silver iodide pyrotechnic flares, PV-26, and 2) liquid nitrogen generator of fine-dispersion ice particles.

A 3-cm weather radar system, ACSOPRI-E, was installed in 1999 in 80 km to southwest from Yazd, and the second radar system was deployed in the southeast of the Project territory at the end of 2000.

The radars operate in volume-scan modes to display and record the 3-D structure of clouds and precipitation every 10 minutes over an area of radius 200 km.

Statistical evaluation of the effectiveness of regular cold cloud seeding operations, carried out in the Central plateau of Iran during three winter seasons of 1999-2001, has showed that from 0,7 to 1,9 km3 of additional water was obtained, which is about 22-40% of the natural seasonal precipitation amount.

The results obtained during the first three seasons under this Project seem optimistic to enhance water resources in the Central plateau of Iran.

Project activity in 2004-2007

Taking into account the promising results of the first three seasons of the Project, in 2004 two domestic An-26 aircraft have been equipped with a basic research instrument package and technical means for cloud seeding.
(image right: example of An-26 aircraft, from

The field activity on seeding of clouds using two equipped aircraft, An-26, continued [into the] 2006-2007 season.

The area of the Project was extended to 500,000 km2 (radius 400 km around Yazd). 77 flights were carried out over the Project territory from 26 November 2006 to 1 April 2007.

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