WMOD00532

• Title: The Rain Stimulation Campaign in Panama Summer 1983
• Date: 6/1/1984
• Weather Modification - Doc Type: Report

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Number of "'rainy" days.
1 June - 31 Aug., 1972-82

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Figure 6. -1983 summer-season number of rainy days and
rainfall per rainy day compared with those of ell!Ven past
seasons (1972-1982) and with the regression of rainy-da:v
rainfall on number of rainy days.

General cloud physics. There has been an effort
lately to associate seeding responses, positive and
negative, with major cloud characteristics such as
temperatures of cloud bases and tops, size and strength
of updrafts, etc. The data base is the growing number of
cloud seeding operations worldwide, now 200 or more,
that have been documented well enough to permit
detailed review. This review tends to confirm an
important feature of the cloud model approach: convec-
tive clouds of moderate depth responded positively to
seeding while those already reaching nearly to the
tropopause responded negatively,

Conclusions concerning assessment. No confident
scientific evaluation of the brief Panama operation was
expected, and none appears possible on the basis of the
data gathered, Nevertheless, the effort at assessment
has not been entirely unrewarding.

The only assessment methods found applicable, one
objective based on specific raininess, and the other
subjective based on visual observation, both indicated
positive responses to the seeding. These indications
were fully consistent with diagnostic calculations of
response based on cloud models and general consider-
ations of cloud physics.

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