|
Items in cart [0] |
Questions? Call 888-624-8373 |
PAPERBACK + PDF PAPERBACK PDF BOOK PDF CHAPTERS Free Resources |
||||||||||||||||
|
||||||||||||||||
|
|
|||||||||||||||
| Copyright © 2009. National Academy of Sciences. All rights reserved. Terms of Use and Privacy Statement |
Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 114
CGlossary
These definitions were generated and modified by the Committee and report
reviewers and from the American Meteorological Society glossary, o'er edition (20004; the
latter are denoted with an asterisk God.
*Accretion: In cloud physics, the growth of an ice l~'drometeor by collision with
supercooled cloud drops that freeze wholly or partially upon contact.
Aerosol: Suspension of solid or liquid particles in ails or gas (as smokes fog, of mist).
*Anthropogenic: Hu~na~-i~duced or resulting from human activities
Bin models: Cloud models in which the size distribution of particles is specified over
discrete intervals (bins).
Blocking (or block design experimentation): Separating experimental units that are
known before the experiment to be similar in some way (e.g., the same type of cloud in
two different locations, say the windward and leeward side of a mountain, where each
location is considered a block); randon~iza''on of experiments there is carried out ire each
block. Blocks restrict randomization by accounting for important outside variables (e.g.,
location) by incorporating those variables into tl~e experimental design.
Cloud condensation nuclei (CCN): Particles, either liquid or solid, upon which water
vapor condenses and forms cloud drops in the atmosphere.
Cloud liquid water: The amount of non-precipitating liquid water in a cloud, usually
measured in gm~3.
* Cloud seeding: The introduction of agents into a cloud to alter the phase and size
distribution of cloud particles for the purpose of modifying its development or increasing
its precipitation. The most frequently used agents are silver iodide, granulated solid
carbon dioxide (dry ice), and salt.
114
OCR for page 115
A PPEIN7DIX C
115
* Coalescence: In cloud physics, the merging of two water drops into a single larger
drop after collision.
* Cold (supercooled) cloud: A cloud composed of s~pe~^cooled wate'A drops.
* Condensation: The physical process by which a vapor becomes a liquid; the opposite
of evaporation.
Covariates: Measurement of two or more variables against each other over time to see
how they vary together.
Cross-over: A technique in which the same site is used alternately in a randomized
scheme both for experimentation and control to minimize location-specific bias.
Deposition: The physical process that occurs in subfreezing air when water vapor
changes directly to an ice without Seconding a liquid first; the opposite of sublimation.
Double-blind: A type of experiment in which neither the experimenters nor the
evaluators know which subjects were treated; this is done to remove all human bias in
evaluation. Specifically in weather modification, both the experimenters and the
evaluators are unaware of which clouds are being seeded until after the experiment is
completed and the results have been evaluated.
Dynamic seeding: Seeding to increase a cloud's potential for rainfall by causing it to
grow larger and last longer than it would have grown without seeding. Transformation of
water droplets to ice crystals is sought to release the latent heat of fusion to enhance
buoyancy and invigorate cloud growth.
Glaciogenic seeding: Process of enhancing ice content in clouds either by nucleating
new crystals or freezing cloud droplets.
Ground generators: In weather modification, usually refers to silver iodide smoke
generators that are operated from the grouted (as opposed to airborne equipment).
* Graupel: Heavily rinsed snow particles, often called snow pellets.
Homogeneous nucleation: Nucleation that occurs without the intervention of a pre-
existing foreign particle.
* Hydrometeor: Any product of condensation or depositions of atmospheric water
vapor, whether formed in the free atmosphere or at the Earth's surface; also, any water
particle blown by wind from the Earth's surface.
Hygroscopic: The ability of condensation nuclei to absorb water and thus to accelerate
the condensation of water vapor.
OCR for page 116
I16
A PPE.NDLY C
Hygroscopic seeding: Process of enhancing water droplet size distribution in clouds by
introducing hydroscopic nuclei with the objective of rain enhancement or hail
suppression.
Mixed-phase cloud: A cloud in which ice particles are intermingled with s'~pe~coole~
water drops.
* Negative cloud-to-ground lightning: A lightning Isle or stroke between a cloud and
the ground that lowers a negative charge to the ground.
* Nowcast: A short-term weather forecast, generally for the next few hours.
* Nucleation: The initiation of a phase change of a substance to a lower themodynamic
energy state (i.e., vapor to liquid condensation, vapor to solid depositions, or liquid to
solid freezing).
Nuclei: A particle of any nature upon which, or the location at which, molecules of
water or ice accumulate as a result of a phase change to a more condensed state; an agent
of 'nucleation.
Null hypothesis: The statement being tested in a test of significance which is designed
to assess the strength of evidence of a claim; the null hypothesis often is the reverse of
what the experimenter believes, put forth to be contradicted by the data.
Orographic cloud: A cloud whose form and extent is determined by the disturbing
effects of orography (i.e., mountains), which causes lifting and condensation in the
passing flow of air. Because these clouds are linked to the terrestrial relict, their location
changes very slowly, if at all.
Overseeding: Condition in a cloud where an excess of nuclei are available, thereby
creating a competition for the available cloud droplets or water vapor, possibly
preventing any of them from growing to the appropriate size necessary to reach the
ground.
* Positive cloud-to-ground lightning: A lightning flash off stroke between a cloud and
the ground that lowers a positive charge to the ground.
Pre-screening: The removal of some weather or closed conditions for consideration in
the design of an experiment before randomization on the balance is made. This is done to
focus the experiment on the conditions of interest.
Randomization: The use of chance to determine experimental units to minimize the
sources of bias on the results. Specifically in weather modification, the design of
experiments by dictating that, for example, "seed" or "don't seed" decisions be made
purely randomly.
OCR for page 117
A PPEA~DIX C
117
Replication: Repeating each experiment on a large enough number of subjects to allow
the systematic effects of the experiments to be seen; it reduces the role of chance
variation and makes the experiment more sensitive to differences among experiments.
Re-randomization: Also known as resampling or Monte-Carlo tests, it is the
construction of artificial datasets using a collection of real data on which experiments are
rerun with seed and no-seed allocations selected at random. The percentage of such re-
randomized seeding effects float exceed the actual real result is the probability of the real
result occurring by chance.
Riming: The rapid f eezing of supercooled water droplets as they impinge upon an
exposed object and accrete to it.
Snowpack: The amount of annual accumulation of snow at higher elevations.
Static seeding: A strategy for optimum nucleation; exploiting the preexisting situation
where less-than-optimal ice crystal concentrations exist, which leads to prolonged periods
of supercooled watet, with no attempt to modify the dynamics of the seeded clouds.
halt.] Influencing precipitation formation processes by changing the microphysics of the
cloud.
* Supercooled water: Liquid water at temperatures below the freezing point (0°C of
32°F).
Variance: A measure of the spread about the mean if the mean is a measure of the center
of a group of observations; it is defined as the average of the squared deviations of a
value from its mean. The variance also is the standard deviation squared.
Warm cloud: A cloud composed of liquid water drops at temperatures above the
freezing point (O°C or 32°F).
Representative terms from entire chapter:
size distribution
