Precipitation Enhancement Project: 25 years since
the Site Selection Phase 2
group of colleagues and friends gathered in Valladolid,
Spain, in May 2005 to remember the project in which they had
participated 25 years before and to reflect on the progress
of precipitation enhancement science since then. That
project was the WMO Precipitation Enhancement Project (PEP).
the early 1979s, a large number of "rain
enhancement" and "hail prevention" projects had been run by several
countries and there was a need for some definitive
indication of whether they were scientifically justified, or
not, as well as guidance on ways to improve the efficacy of
such projects. Recognition
of that need and the hope that a well-conducted
international project would gain wide acceptance led to the
Precipitation Enhancement Project. The project had its
origins in deliberations of the Panel on Weather
Modification in Toronto, Canada, in 1974, under the
chairmanship of Professor Roland List, and was formally
established in 1975 by the approval of World Meteorological
Congress. The aim of the project was to create a
scientifically planned and executed project of precipitation
enhancement that could serve Member countries as an example
for worldwide practice.
The magnitude of the project was ambitious: US$ 3
project was placed in the hands of the Intergovernmental
Board consisting of representatives of interested countries
(W. Godson, Canada; J. Zillman, Australia; B.J. Mason, UK;
Y. Israel, USSR; R. Wright and G. Benton, USA).
Board initiated the search for a suitable site for the
experiment by charging a group of prominent scientists that
included J. Warner (Australia), A. Gagin (Israel) and E.
Bolley and R. Cunningham (USA) to visit potential host
countries. This led to the selection of the site in the vicinity of
Valladolid, Spain, and to the Site Selection Phase 2 (SSP2)
that became three years of observations (1979-1981) of
clouds by aircraft, radar and satellites to determine the
potential for augmentation of precipitation by cloud
cloud seeding was to take place during this phase, just the
assessment of the potential for profitably doing so.
celebration in May 2005 coincided with the 25th
anniversary of the fiesta in the Castle of Fuensaldaa
that marked the end of the second (middle) year of the field
was also almost 30 years since the formulation of
the idea for PEP.
conclusion of the SSP2 studies was that the potential for
significant rain augmentation in the region, during the
winter months, was insufficient to warrant a full-scale
seeding effort. Although
the result of PEP was negative in that sense, it did,
however, serve the useful role of foreclosing an experiment
that would probably have failed and, much more importantly,
set an example for the logical and non-political planning of
weather modification efforts. This aspect of PEP was the
keynote of the 25th reunion.
project had a significant impact on scientific work
and international collaboration within the National
Meteorological Institute (INM) of Spain: an aspect of PEP
that was manifest in the talks given during the reunion by
various directors and group leaders from the INM.
Vali et al.