WMOD00269 ‎(2)‎

• Contract/Permit #: 02FC810810
• Title: Weather Damage Modification Program for Cooperative Weather Research between States and the US Department of Interior, Bureau of Reclaimation
• Date: 11/19/2002
• Weather Modification - Doc Type: Report

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A.3.2.1

Modeling and field studies

Modeling and field experimentation efforts should be conducted to establish the details
of the relevant microphysical-dynamical process in clouds and their responses to
hygroscopic and glaciogenic seeding. Because the scientific evidence indicates that
precipitation increases can be produced by seeding on the scale of the treated clouds
and convective cells, the initial stages of a future research effort should focus both
observationally and with modeling on how these treated entities communicate to clouds
on larger scales, presumably through enhanced and better-organized downdraft
outflows.

A.3.2.2

Replication of results

The results from any seeding experiment in one region cannot automatically be
transferred to a new geographic area. Land-surface characteristics, background
aerosol characteristics, and differences in general synoptic situations, are important
parameters that will impact the feasibility and impact the seeding programs. ... The
results from the hygroscopic seeding experiments on individual convective clouds call
for a replication in the United States to provide the physical as well as statistical
evidence needed to establish the proof-of-concept. This could best be obtained by
conducting a randomized experiment that will include a strong physical component.

A.3.2.3

Cost-benefit

The important next step is to demonstrate that cost-beneficial increases in rain could be
achieved on an area-wide basis at the surface. Another important aspect in this regard
is hydrological studies that will need to be addressed to assess the full economical and
societal impact of any rain augmentation program.

A.3.3 Task C - Thunderstorm Hail Mitigation Studies

In recent years, crop-hail losses in the United States have typically been around $2.3
Billion annually. In the High Plains, the loss from hail is 5 to 6 % of the crop value.
Susceptibility to damage depends upon the crop type, the stage of development, the
size of the hail, and also the magnitude of any wind accompanying the hailfall. Property
damage from hail in recent years has been on the same order as crop-hail damage,
usually topping the $2 billion mark, sometimes more.

T~e great variability of hail impairs the capability of any hail suppression experiment
over a small target area (typically of the order 1,000-2,000 km2) to produce a definitive
statistical result. However, operational hail suppression projects continue in several
places in the United States (North Dakota, Kansas, Oklahoma) and in many other parts
of the world. Results of operational hail suppression programs in the United States
have been based upon analyses of crop-hail insurance data. The North Dakota Cloud
Modification Project reports reductions in crop-hail damage on the order of 45%, while
the Western Kansas Weather Modification Program reports reductions in crop-hail
losses of 27%. The AMS Policy Statement (1998) on planned and inadvertent weather
modification states that such use of these data is questionable, and that statistical
evaluations using hail characteristics (Le., kinetic energy, hailstone size, and area of

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