WMOD00519

• Project Name: Weather Modification Programme - Precipitation Enhancement Project
• Title: A Review of the Hydrological Aspects of Evaluation of Precipitation Enhancement
• Date: 5/1/1977
• Weather Modification - Doc Type: Report

-'-'"; .-""~-;--=-;---",;.~:;,-'.-;.;;;.,...o=-=~-'~_",__-,,,. _. ... _ . _. _ m __ _. <'. . '--.--~-~-_.___~__________..-",--._-:.

...-.... ,r-o.

OBJECTIVES OF PEP

The r~10 Executive Committee, at its twenty-eighth session in 1976, defined
the ~cientific objectives of the Precipitation Enhancement Project as follows:

(a) To provide Members Vii th reliable information about the probabilities of
successful artificial intervention in meteorological processes with the
object of increasing the amount of precipitation over an area of the or-
der of 10 000 km2. The size of the area for the proposed project (i.e,
the target and nearby control areas) should be somewhere around 50 000
km2, a scale large enough to provide adequate evaluation of scientific
feasibility and economic benefit, but small enough to permit the use of
adequate methods for seeding and observations;

(b) To demonstrate, at a satisfactory statistical significance level over a
relatively short experimental period (five years), that any increase ob-
served is not a chance event but is associated with the seeding. The
principal evaluation of this experiment will be in terms of precipi-
tation at the ground;

(c) To obtain sufficient understanding of the meteorology and cloud physics
in the area of the experiment to ensure that the statistical association
of seeding, and any increase in precipitation, will be generally accept-
able as a cause-and-effect relationship;

(d)

To make an examination outside the target area in
whether any benefits of seeding extend over areas
target area, or whether there has merely been a
redistribution of precipitation;

order to determine
greater than the
comparatively local

(e)

To make systematic measurements, varying from mesoscale
structure, in order to develop additional co-variatct. to
power of the statistical analysis;

to cloud micro-
strengthen the

(f) To obtain well-documented scientific evidence that may lead to tht~ opti-
mization of the effects of seeding. For this purpose, a series of sys-
tematic cloud physics measurements should be token on a routine basis.
This would allow the application of statistical stratification techniques
to relevant physical parameters, and could shed more light on the quanti-
tative aspects of seeding techniques;

(g) To be able to make some recommendations about the applicability of the
PEP procedures to other areas of the world;

(h) To assess the environmental impact of precipitation-enhancement activities,
both within and outside the experiment target area.