1o' mailer of this Treat}', have jeopardized the supreme interests
17 of its country. It shall give notice of such withdrawal to all
18 olher Parties to the Treaty three months in advance.
V.) Article VI
20 "1. This Treaty shall be open to all States for signature.
21 Any State which docs not sign this Treaty before its entry
22 into force in accordance with paragraph 3 of this Article
23 may accede to it at any time.
24 "2. This Treaty shall be subject to ratification by sig-
25 natory States. Instruments of ratification and instruments of
1 accession shall be deposited with the Governments of the
3 which are hereby designated the Depositary Governments.
4 "3. This Treaty shall enter into force after its ratifica-
5 tion by the States, the Governments of which are designated
6 Depositaries of the Treaty.
7 "4. For States whose instruments of ratification or ac-
8 cession are deposited subsequent to the entry into force of
9 this Treaty, it shall enter into force on the date of the de-
10 posit of their instruments of ratification or accession.
11 "5. The Depositary Governments shall promptly inform
12 all signatory and acceding States of the date of each signa-
13 ture, the date of deposit of each instrument of ratification of
14 and accession to this Treaty, the date of its entry into force,
15 and the date of receipt of any requests for conferences or
16 other notices.
17 "6. This Treaty shall be registered by the Depositary
18 Governments pursuant to Article 102 of the Charter of the
19 United Nations."
Reported Cases on Weather Modification
Slutsky v. City of Neiv York, 197 Misc. 730, 97 N.Y.S. 2d 238 (Sup. Ct, 1950).
Southwest Weather Research, Inc. v. Rounsaville, 320 S.W. 2d 211 (Tex. Civ.
App., 1958), and Southicest Weather Research, Inc. v. Duncan, 319 S.W. 2d
940 (Tex. Civ. App. 1958), both affd. sub nom. Southwest Weather Research, Inc.
v. Jones, 160 Tex. 104, 327 S.W. 2d 417 (1959) .
Summerville v. North Platte Valley Weather Control DIM., 170 Neb. 46, 101
X.W. 2d 748 (1960).
Pennsylvania Natural Weather Assn. v. Blue Ridge Weather Modification
Assn., 44 Pa. D. & C. 2d 749 (1968) .
Glossary of Selected Terms in Weather Modification 1
ACRE- FOOT— The volume of water required to cover
one acre to a depth of one foot: 43,560 cubic feet,
AEROSOL— A colloidal system in which the dispersed
phase Is composed of either solid or liquid particles,
and in which the dispersion medium is some gas.
There is no clear-cut upper limit to the size of
particles comprising the dispersed phase in an aerosol,
but as in ail other colloidal systems, it is rather com-
monly set at 1 micron. Haze, most smokes, and some
fogs and clouds may thus be regarded as aerosols.
AIRCRAFT SEEDING— The use of aircraft to dispense
cloud seeding agent*.
ALTOCUMULUS— A principal type of cloud, 8,000 to
20,000 feet, consisting of a layer where the denser
parts have modified cumuliform characteristics of
roundness and sharpness of outline.
ALT08TRATU8 — A principal type of "middle" cloud
(altitude approx. 8,000 to 20,000 feet), appearing
as a fairly uniform grey layer that often covers the
ANVIL CLOUD— Popular name given to a cumulonim
bus cloud whose upper, ice-crystal portion is spread
out horizontally to give the appearance of an anvil.
In the International Cloud Classification, this is a
"cumulonimbus caplllatus" cloud with the supplemen
tary feature "incus."
ARTIFICIAL NUCLEATION — Any process whereby
the nucleation of cloud particles .s Initiated or accel-
erated by human intervention.
CAP CLOUD -An approximately stationary cloud, on
or hovering above an Isolated mountain peak. It is
formed by the cooling and condensation of humid air
forced up over the peak.
CELLULAR CONVECTION — An organized, convecUve.
fluid motion characterized by the presence of distinct
convection cells or convectlve units, usually with up-
ward motion (away from the heat source) in the cen-
tral portions of the cell, and sinking or downward flow
in the cell's outer regions.
CHAFF— Metallic, electrical dipoles, several centime-
ters long, commonly made of fine wire.
The original use of chaff, dropping large quantities
of It from aircraft in WWII, was to jam enemy radars
It is now used experimentally to alter the electrical
properties of thunderstorms.
CHAFF SEEDING -The dispensing of chaff into a cu-
mulonimbus cloud for the experimental purpose of
altering the cloud's electrical structure and hence
affecting the occurrence and character of lightning.
It is hypothesized that the chaff is the medium for
leakage currents (through corona point discharges)
which forestall the development of the charge centers
necessary for lightning tormatioa
CIRRUS — A principal cirriform cloud type, composed of
ice crystals aggregated into delicate wisps or patches
at high altitudes.
The term "cirrus" is often used as a generic term
for ail cirriform clouds.
CLOUD — A visible aggregate of minute water and/or
ice particles in the atmosphere above the earth's
surface. Cloud differs from fog only In that the latter
is, by definition, in contact with the earth's surface.
Clouds form in the free atmosphere as a result
of condensation of water vapor In rising currents of
air, or by the evaporation of the lowest stratum of
fog. For condensation to occ\ir at the point of satura-
tion or a low degree of supersatu ration, there must
be an abundance of condensation nuclei for water
clouds, or ice nuclei for ice-crystal clouds. The size of
cloud drops varies from one cloud type to another,
and within any given cloud there always exists a fin-
ite range of sizes. Generally speaking, cloud drops
range between one and one hundred microns in di-
ameter, and hence are very much smaller than rain
cloud physics dealing with extremely small-scale phe-
nomena, particularly the molecular-scale processes of
evaporation, condensation, and freezing of cloud par-
ticles, and the complex Interactions, Including elec-
trical effects, among cloud particles.
CLOUD MODEL — In general, any idealized represents
tkon of a cloud or cloud processes. Increasingly, this
term is used for mathematical representations of cloud
processes, particularly those formulated for numerical
solution on electronic computers
CLOUD MODIFICATION -Any process by which the
natural course of development of a cloud is altered by
CLOUD PHYSICS -The body of knowledge concerned
with physical properties of clouds in the atmosphere
and the processes occurring therein
CLOUD SEEDING — Any process of injecting a sub-
stance into a cloud for the purpose of influencing the
1 From Project Skywater ; 1973-74 Biennial Report. U.S. Department of the Interior.
Hur»-nu of Reclamation. Division of Atmospheric Water Resources Management. REC-ERC-
70-21. Denver, December 1976. pp. A-21 to A-25.
fers to the injection of a nucleating agent, but some-
times alludes to substances which do not directly
affect nudeation (such as carbon black).
CLOUD SEEDING AGENT- Any variety of substances
dispensed for the purposes of cloud seeding. In addi-
tion to the commonly used silver Iodide and dry ice,
a number of other materials have been experimented
with for various purposes, for example: calcium chlor-
ide, urea, metaldehyde, chlorosulfonlc acid, carbon
black, common salt, and water spray.
COALESCENCE — In cloud physics, the merging of two
water drops into a single larger drop.
COALESCENCE EFFICIENCY -The fraction of all col
lis ions between water drops of a specified size which
result in actual merging of the two drops into a single
CONDENSATION — The physical process by which a
vapor becomes a liquid or solid; the opposite of evap-
oration. In meteorological usage, this term is applied
only to the transformation from vapor to liquid; any
process in which a solid forms directly from Its vapor
is termed sublimation, as is the reverse process.
CONDENSATION LEVEL -That level in the atmos-
phere at which saturation and hence condensation,
will occur in a column of rising air. This occurs by
virtue of the adlabatic cooling of the air as it rises.
CONDENSATION NUCLEUS — A particle, either liquid
or solid, upon which condensation of water vapor be-
gins in the atmosphere. See nudeation.
CONTROL CLOUD— In doud seeding experiments on
Individual douds, a. doud chosen to remain unseeded,
but is otherwise monitored as if it had been, in order
to provide data for comparison with seeded douds.
CONVECTION— 1. In general, mass motions within a
fluid resulting in transport and mixing of the proper-
ties of that fluid.
2. As specialized in meteorology, atmospheric motions
that are predominantly vertical, resulting in vertical
transport and mixing of atmospheric properties.
CONVECTION CURRENT — (or convective current)
Any current of air involved in convection. In meteor-
ology, this Is usually applied to the upward moving
portion of a convection circulation, such as a thermal
or the updraft In cumulus douds.
CUMULI FORM - Llxe cumulus; generally descriptive of
all douds, the principal characteristic of which Is ver-
tical development In the form of rising mounds, domes,
CUMULONIMBUS— ( Commonly called thundercloud,
thunderhead, thunderstorm.) A principal doud type,
the ultimate stage of development of cumulus or con-
vective douds. They are very dense and very talL
commonly 5 to 10 miles In diameter and sometimes
reaching a height of 12 miles or more. The upper
portion Is at least partly composed of ice crystals,
and often takes the form of an anvil ("Incus") or
vast plume The base of the doud Is Invariably dark
and often accompanied by low, ragged douds.
CUMULUS — A principal doud type, actually a doud
"family" all of which are characterized by vertical
development; a convective doud.
DEFTV88ION — In meteorology, the exchange of fluid
parcels (and hence the transport of conservative prop
erties between regions In space. In the apparently
random motions of a scale too small to be treated by
the equations of motion.
In meteorology, the diffusion of momentum (vis-
cosity), vortlclty, water vapor, heat (conduction),
particulate matter, and gaseous components of the
atmospheric mixture, have been studied extensively.
The atmospheric motions diffusing these properties
may in many cases be of much larger scale than the
molecular, the exchanging parcels being called eddies,
and the diffusion equation extended by analogy to
DOPPLER EFFECT— (Also called Doppler shift) The
change In frequency with which energy reaches a
receiver when the receiver and the energy source are
in motion relative to each other.
DOPPLER RADAR— A radar which detects and inter
pre is the Doppler effect in terms of the radial velocity
of a target The signal received by a radar from a
moving target differs slightly In frequency from the
Doppler radar la widely used In doud studies
because it enables the deduction of the motions of
doud and precipitation partides.
DRY-ICE- Solid carbon dioxide (CO 2 ). It evaporates
directly from solid to gas at a temperature of -78. 5* C
DRY-ICE SEEDING — The dispensing of dry-ice pellets
Into supercooled douds for the purpose of transform
Ing the supercooled droplets Into ice crystals, which
then grow and fall out Dry ice creates a sufficiently
cold environment around the droplet* for them to
undergo spontaneous nudeation
ECHO— In radar, a general term for the appearance,
on a radar Indicator, of the radio energy returned
from a target More explicitly, It refers to the energy
reflected or scattered back from a target
FREEZING NUCLEUS — Any particle which, when pre
growth of an Ice crystal about itself (see nudeatlon).
GLACIATION— In cloud physics, the transformation of
cloud particles from water drops to ice crystals
GROUND GENERATOR— In weather modification, al
most invanabh referring to silver iodide smoke gen
erat/>rs that are operated on the ground (as opposed
to airborne equipment).
HAIL SUPPRESSION — Any method of reducing the
damaging effects of hailstorms by operating on the
hail producing cloud.
The currently prevailing hypothesis is that silver
iodide seeding provides more hailstone nuclei (and, at
the same time, reduces the amount of supercooled
water available to build up large hailstones) with the
net effect that the hail that reaches the ground Is
smaller and less damaging, and also has a higher
probability of melting before reaching the ground
HYGROSCOPIC NUCLEI — Condensation nuclei com
posed of salts which yield aqueous solution., of a very
low equilibrium vapor pressure compared with that of
pure water at the same temperature. Condensation
of hygroscopic nuclei may begin at a relative humidity
much lower than 100 percent (about 75 percent for
sodium chloride), while on so-called non- hygroscopic
nuclei, which merely furnish sufficiently large (by
molecular standards ) wettable surfaces, relative hu-
midities of nearly 100 percent are required. "Damp
haze" is formed of hygroscopic particles In the process
of slow growth in relatively dry air
HYGROSCOPIC SEEDING -Cloud seeding with hygro
scopic material which encourages condensation and
collect* water vapor
ICE CRYSTAL— Any one of a number of macroscopic
crystalline forms In which ice appears, Including hex
agonal columns, hexagonal platelet*, dendritic cry
stals, ice needles, and combinations of these forms
I IE CRYSTAL CLOUD- A cloud consisting entirely of
ice crystals (such as cirrus); to be distinguished in
this sense from water clouds and mixed clouds
ICE NUCLEUS - Any particle which serve* as a nucleus
in the formation of ice crystals In the atmosphere,
used without regard to the particular physical process
involved in the nucleation.
Due to an apparent scarcity of natural ice nuclei
(or. at least, freezing nuclei) in the atmosphere, cloud
-eeding with ice- nucleating agents become* a practi
cal endeavor Both sliver iodide and dry ice perform
the function of nucleating ice in an aggregate of su
percooled water droplet*
ICE- PHASE SEEDING -Cloud seeding with an agent
which serves as an artificial ice nucleus.
ISOHYET — A line drawn on a map connecting geo
graphical points having equal amounts of precipitation
during a given time period, or for a particular storm
LIQUID WATER CONTENT — ( Abbreviated LWC. (The
amount of liquid water (that is, not counting water
vapor) in a cloud, usually expressed as grams of
water per cubic meter of cloud volume.
MESO-SCALE— In meteorology: having characteristic
spatial dimensions somewhere between 1 and 100
miles, usually implying between 5 and 50 miles.
NUCLEATING AGENT — (or nucleant) In cloud phy-
sics, any substance that serves to accelerate the nu
cleation of cloud particles Nucleating agents may
themselves be nuclei (silver iodide, salt, sulfur di
oxide, dust ) or they may enhance the nucleation en-
vironment (dry, ice, propane spray ).
NUCLEATION — Any process by which the phase
change of a substance to a more condensed state
(condensation, sublimation, freezing) is initiated at
certain loci (see nucleus i within the less condensed
A number of types of nucleation are of interest
phase change from vapor to liquid is of decisive im-
portance in analyses of all cloud formation problems.
The physical nature of freezing nuclei which may be
responsible for the conversion of drops of supercooled
water into ice crystals is critically important in pre-
cipitation theory, us is also the clarification of the role
of spontaneous nucleation near -40*C The impor
tance of sublimation nuclei is promoting the growth of
ice crystals directly from the vapor phase is doubtful
NUCLEUS — In physical meteorology, u purticle of any
nature upon which, or the locus at which, molecules
of water or ice accumulate as a result of a phase
change to a more condensed state; an agent of nu
NUCLEUS COUNTER -Any of severul devices for de
termining the number of condensation nuclei or ice
nuclei in a sample of air.
NUMERICAL MODEL— In meteorology, a mathemati
cal formulation of atmospheric processes constructed
so that the dynamical and thcrmodynamical equations
of atmospheric motion can be solved by numerical
methods on electronic computers
OROGRAPHIC CLOUD- A cloud whose lorrn and c\
tent is determined by the disturbing effects ■>( imi
graph>. mountains, upon the passing flow of ,ur Me
cause these clouds are linked with the form of the
at all, although the winds at the same level may be
OROGRAPHIC LIFTING -The lifting of an air current
caused by its passage up and over mountains
OVERSEEDING — Cloud seeding in which an excess of
nucleating material is released. As the term is nor
mally used, the excess Is relative to that amount of
nucleating material which would, theoretically, maxi-
mize the precipitation received at the ground. In
seeding a supercooled cloud with dry ice or silver
iodide, addition of too much seeding material may
create so many ice crystals that none can grow to a
size large enough to fall out of the updraft sustaining
PLUME— The volume of air space containing any of the
substance emitted from a point source.
PRECIPITATION -Any or all of the forms of water
particles, whether liquid or solid, that fall from the
atmosphere and reach the ground
PRECIPITATION ECHO -A Type of radar echo re
turned by precipitation
PRECIPITATION EFFICIENCY — For a given cloud or
storm system, the ratio of the amount of precipitation
actually produced to the maximum amount theoreti-
cally possible by that system.
PRECIPITATION GAGE -General term for any device
that measures the amount of precipitation; princi-
pally, a rain gage or snow gage
PYROTECHNIC GENERATOR -A type of silver iodide
smoke generator in which th^silver iodide forms as
a part of the pyrotechnic fuel mbtture. A great flexi
bility of design is possible with these generators, and
they are capable of an extremely high output of
silver- iodide nuclei.
RADIOSONDE- A balloon borne instrument for the
simultaneous measurement and transmission of mete-
RAIN MAKING -Popular and general term for all
weather modification effort aimed at increasing pre-
RANDOM — Eluding precise prediction, completely Ir-
regular. In connection with probability and statistics,
the term random Implies collective or long-run regu-
larity; thus a long record of the behavior of a random
phenomenon presumably gives a fair indication of Its
general behavior in another long record, although the
individual observations have no discernible system of
RANDOMIZE — To make random. Specifically, in weath
er modification contexts, It refers to the design of
experiments and projects In such a way as to mini
mlze the sources of bias in the evaluation of results
by dictating that "seed" or "don't seed" decisions
(for example) be made on a purely random basis
If the total number of such decisions Is sufficient, ■,
large, this procedure ensures that a comparison of
"seed" versus "don't seed" results contains minimal
REAL-TIME — Nearly Instantaneous.
SALT SEEDING — Cloud seeding with salt particles, a
technique that has been applied to warm (non-super
cooled) clouds and fog on the principle that the hy
groscopic droplets of salt solution will grow at the
expense of other particles.
SEEDING RATE — The quantity of seeding agent (in
grams or kilograms) released either per unit of time
(if applied to ground-based generators) or per unit
of distance (traveled by an aircraft) used in cloud
SILVER IODIDE — (Chemical formula: Agl. ) The com
pound of silver and iodine whose crystalline structure
very closely approximates that of Ice-crystals.
SILVER-IODIDE GENERATOR- Any of several de
vices used to generate a smoke of silver-iodide cry
staJs Most burn an acetone solution of silver iodide;
the other Important (and newer) category is that
of pyrotechnic generators.
SILVER-IODIDE SEEDING — The world-wide "work-
horse" method of cloud seeding, where, by any of
several techniques, silver- Iodide crystals are intro
duced into the supercooled portions of clouds to induce
the nucleation of Ice crystals.
SNOW COURSE -An established line, usually from
several hundred feet to as much as a mile long,
traversing representative terrain in a mountainous
region of appreciable snow accumulation Along this
course instruments (such as snow stakes, radioactive
snow gages) are installed, and/or core samples of the
snow cover are periodically taken and averaged to
obtain a measure of Its water equivalent
STRATOCUMULUS-A principal, low-altitude, cloud
type, consisting of a layer of rounded or roll shaped
elements which may or may not be merged and which
usually are arranged in orderly flies or a wave pat
the solid phase directly to the vapor phase, or vice
versa, without puitng through an intermediate liquid
SUPERCOOLING — The reduction of temperature of any
liquid below the melting point of that substance's
eolld phase; that Is, cooling beyond its nominal freez-
ing point A liquid may be supercooled to varying
degrees, depending upon the relative lack of freezing
nuclei or solid boundary irregularities within its en-
vironment, and freedom from agitation.
SYNOPTIC— In general, pertaining to or affording an
In meteorology, this term has become somewhat
specialized in referring to the use of meteorological
data obtained simultaneously over a aide area for the
purpose of presenting a comprehensive and nearly
Instantaneous picture of the state of the atmosphere.
Thus, to a meteorologist, "synoptic." takes on the
additional connotation of simultaneity.
TARGET AREA — la a weather modification project,
the area within which the effects of the weather mod-
ification effort are expected to be found
TRACER— An easily detectable substance injected into
the atmosphere for the purpose of subsequent mea-
surement and reconstruction of Its history- (trajectory,
diffusion, etc )
TRAJECTORY— (Or path, t A curve in space tracing
the points successively occupied by a particle in mo-
tion. At any given Instant the velocity vector of the
particle Is tangent to the trajectory.
WARM CLOUD— In weather modification terminology,
a water doud that is not a supercooled cloud La,
that exists entirely at temperatures above 0*C.
WATER EQUIVALENT— The depth of water that would
result from the melting of the snowpack or of a snow
tore.) Water substance In vapor form: one of the
most Important of all constituents of the atmosphere.
WEATHER MODIFICATION — The Intentional or In-
advertent alteration of weather by human agency.
WEATHER RADAR -Generally, any radar which Is
suitable or can be used for the detection of precipi-
tation or clouds.