cloud seed·ing (kloud s?d?ng) noun
The technique of stimulating rainfall, especially by distributing dry ice crystals or silver iodide smoke through clouds.

Excerpted from The American Heritage Dictionary of the English Language, Third Edition Copyright © 1992 by Houghton Mifflin Company. Electronic version licensed from Lernout & Hauspie Speech Products N.V., further reproduction and distribution restricted in accordance with the Copyright Law of the United States. All rights reserved.

According to the article referred to, الاستمطار is the general term for stimulating rain, and بذر السحب the term for "cloud seeding".

I agree with the others' suggestions. But maybe this is the term needed. it goes with the Quranic verse "وجعلنا الرياح لواقح"

بذر السحب

Cloud seeding is the process of inducing condensation of water vapor in the air to form rain bearing clouds. This can be done by dropping ice or certain chemicals from airplanes. I used the word استجماع to allude to the underlying concept of artificial condensation. You might also say اصطناع السحب to simply refer to the artificial formation of clouds, although this may imply that they are formed from nothing, which is not the case. Cloud seeding can be conidered analagous to crystalization, where you place a small crystal in a solution to obtain a large crystal, i.e. you have to have something to begin with.

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Note added at 1 day 8 hrs 14 mins (2004-04-22 03:35:40 GMT)
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The following quote from a colleague describes part of a lecture by Sheikh Trarik Al-Soweidan that is consistent with Mueen Issa\'s explanation above:

\"He spoke at length at different aspects of إعجاز one of which was this particular point adding that while it is known that الرياح تعتبر لواقع للنباتات, it is now very clear from the ayah 22 of surat Al-Hijr 15 :
بسم الله الرحمن الرحيم: وأرسلنا الرياح لواقح فأنزلنا من السماء ماء فأسقيناكموه \" can refer to the winds as لواقح للغيوم أو السحب وأنها هي التي تتسبب في إنزال المطر بإذن الله.

The Sheikh explains that Allah (SWT) here speaks about the
winds and the rain where the fa in فأنزلنا indicates the
immediate action فورية. \"