A cloud seeding
operation in which an excess of nucleating material is released over that required to produce the desired effect.
As the term is normally used, the excess is relative to that amount of nucleating material expected to produce the maximum amount of precipitation
received at the ground. For example, in seeding
a supercooled water
cloud with dry ice
or silver iodide
in order to increase precipitation, the addition of too much seeding material will create too many ice crystals
insofar as they compete for the available water vapor
, and few of them will grow large enough to fall as precipitation. There are unresolved questions about what composes the optimal amount of seeding material to produce the desired effect. These questions include how to estimate the right amount of material and when and where to deliver it to the cloud
; it is difficult to assign quantitative values that will result in overseeding. See cloud seeding
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