Alistair Fraser

Alistair Fraser

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46
Publications
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763
Citations

Publications

Publications (46)
Article
Based on his interactive visualization Web site, the author explores the Web as a tool to build better metaphors for students and emphasizes the pedagogical power of the medium, which, he asserts, remains largely untapped. Discussion includes the use of temporal, special, and parametric process models to increase the pedagogical value of teaching w...
Article
This page addresses some common misperceptions in the field of meteorology that are often perpetuated by educators. The examples are about the shape of raindrops, the reason clouds form when air cools, the cause of the greenhouse effect, and whether the water rotation direction in a sink (or toilet) as it drains depends on Coriolis forces and which...
Article
Some dew-covered plants are strongly retroreflective. The bright glow seen when the antisolar point falls on grass is known as the heiligenschein. Its widely accepted explanation requires that the grass be covered with hair. The discovery of the sylvanshine, a closely related phenomenon best seen at night, revealed that strong retroreflection can o...
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Full-text available
Subsuns, Bottlinger's rings, and elliptical halos are simulated by the use of a Monte Carlo model; reflection of sunlight from almost horizontal ice crystals is assumed. Subsuns are circular or elliptical spots seen at the specular reflection point when one flies over cirrus or cirrostratus clouds. Bottlinger's rings are rare, almost elliptical rin...
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Full-text available
Green thunderstorms are observed occasionally, yet with one exception they have received no scientific attention, experimental or theoretical. Fraser suggested that thunderstorms themselves are not green but that a thick thunderstorm provides a dark backdrop for green airlight near sundown. Greenness is a consequence of reddened sunlight illuminati...
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Full-text available
The visual phenomenon called virga, a sudden change in the brightness of a precipitation shaft below a cloud, is commonly attributed to evaporation of raindrops. It is said to be rain that does not reach the ground. The optical thickness of an evaporating rain shaft, however, decreases gradually from cloud base to ground. Thus, it is more likely th...
Article
Newton asserted without proof that a zero-order rainbow exists, one associated with two refractions and no reflection. Subsequent authors also postulated such a rainbow but argued that it is not seen because its angular position (26 deg) is too close to the Sun. But it is not seen because it does not exist. Newton's erroneous 26-deg rainbow appears...
Article
The Maple Leaf Flag has proven to be an outstanding symbol. Following Confederation, Canada waited nearly a century to establish its national flag, a lacuna which did not result from indifference. It stemmed from the ambiguities of both national identity and flag protocol — ambiguities which became manifest in the informal flags used and proposed....
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Full-text available
A statistical pattern recognition technique called IREW is described. IREW has several strengths, such as fast execution, small storage requirements, and increments learning, that may make the technique useful for many meteorological pattern recognition problems. A weakness of IREW is that it may not recognize complex patterns as well as more sophi...
Article
Easy and reliable estimates of plant canopy structure are needed for many applications but direct measurements are laborious and often destructive. A technique for indirectly sensing canopy structure from simple, manageable measurements of sunlight transmitted through the canopy is examined. The integral relationship between sunlight transmission a...
Article
At altitudes greater than a few kilometers the horizon is indistinct because of contrast reduction, even on extraordinarily clear days. An airplane passenger flying over an ocean cannot point to the apparent boundary between earth and sky and confidently proclaim its distance. To determine the distance to the horizon to within 10% requires knowing...
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Scitation is the online home of leading journals and conference proceedings from AIP Publishing and AIP Member Societies
Article
Although the spectra of drop radii in rain showers are broad, the supernumerary bows are caused by only those drops with radii of about 0.25 mm. The angle of minimum deviation, the rainbow angle, is a function of drop size, being large for big drops, owing to drop distortion, and large for small drops, owing to interference. Between these extremes,...
Article
An analytic sun pillar model is developed which indicates that large hexagonal ice columns can cause sun pillars. The model shows that the Stuchtey method for explaining sun pillars is not incorrect, only incomplete. The model uses an expression for the intensity of the sun pillar that considers both the optical mapping of light for a single crysta...
Article
It is shown that, contrary to classical theory, the circular halos need not be caused by randomly oriented crystals. Furthermore, if Brownian motion is the disorienting mechanism then the circular halos cannot be caused by the randomly oriented crystals, which are too small to produce a reasonably sharp diffraction pattern. However, the circular ha...
Article
Optical data containing the relative positions of an observer, a target, and an image of the target are inverted with a set of nonlinear polynomial equations to obtain a temperature profile near the earth's surface. The temperature that is predicted at a specific height with the inversion of optical data is verified with a temperature that was meas...
Article
The first-known, explicit, analytic optical inversion for a refractive-index profile with curvature is given. It enables a quasi-parabolic profile of height vs temperature to be calculated from observations of the inferior mirage of natural objects. Given sufficient fetch, an inferior mirage will occur anytime the heat flux is away from a horizonta...
Article
Analytic solutions to the refraction and extinction integrals are presented for the case of a horizontally or spherically stratified medium. These solutions are not only useful for the calculation of the images that would be seen through a lens with a continuously varying index of refraction, such as the atmosphere, they also provide a solution to...
Article
Citation Alistair B. Fraser, "Theological Optics," Appl. Opt. 14, A92-A93 (1975) http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-14-4-A92
Article
There has long been speculation about why the green flash can be seen on one day, while on another apparently similar day it cannot. Although the green flash can be produced by a number of different refractive structures in the atmosphere, only one is of consequence when the viewing is done over the irregular terrain of most land surfaces. A combin...
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Full-text available
A model for airflow over mountainous terrain is presented. The equations for steady, two-dimensional, laminar inviscid flow, including pseudo-adiabatic latent heat release, are derived. Approximate solutions to the linearized equations are obtained for stably stratified conditions, and a terrain consisting of broad ridges (width25 km), through an i...
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Full-text available
Expressions are derived for the horizontal and vertical components of the wind, the temperature, and the mass of water vapor condensed when air flows over a long mountainous ridge. The growth of solid precipitation particles in the orographic clouds by deposition from the vapor phase, riming and aggregation are considered. The trajectories of these...
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This site provides an explanation for cloud formation and seeks to correct myths or misconceptions about how clouds form. Water vapor, condensation, and evaporation are discussed in the context of dew-point temperature and saturation. Educators and anyone explaining cloud formation will find hints on how to present the correct information and avoid...
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The answers on this page were written in response to questions from readers of the Bad Meteorology pages. Although the questions presented here are often ones asked by a specific person, each is chosen to characterize a group of similar questions which have been asked about the topic. Topics include: the vapor-holding capacity of air, reasoning and...
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This site contains a series of pages, each with a fact relating to the subject of meteorology, hydrology, or atmospheric science. Each bit of information has to do with the composition, structure or dynamics of the atmosphere including temperature, pressure, and humidity. Educational levels: General public, High school, Middle school
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This site is designed to belie the statement that the greenhouse effect is caused when gases in the atmosphere behave as a blanket and trap radiation which is then reradiated to the Earth. Students will learn that the atmosphere does not act like a blanket, trap radiation, reradiate heat, trap heat, or behave like a greenhouse. In addition, the ana...
Article
This website is designed to sensitize teachers and students to examples of bad science taught in schools and universities, and offered in popular articles and textbooks. Sections include Bad Astronomy, Bad Chemistry, and Bad Meteorology. As an example of bad science, the Pathetic Fallacy, which is the mistake of attributing human qualities to event...
Article
This information is designed to belie the artistic representation of a raindrop as presented by popular culture as a teardrop. Actually, real raindrops bear scant resemblance to this popular fantasy. Students will discover that small raindrops (a radius of less than 1 mm) are spherical; larger ones assume a shape more like that of a hamburger bun....
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This site is intended to clear up several misconceptions about the Coriolis forces or Coriolis Effect. The author explains what is affected and what is not and also explains the reasons why. Several incorrect examples from popular media sources are cited and explained. Educational levels: High school, Middle school, Undergraduate lower division
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This set of Frequently Asked Questions (FAQ) is written in response to questions from readers of the Bad Meteorology pages. Although the questions presented here are often ones asked by a specific person, each is chosen to characterize a group of similar questions which have been asked about the topic. The questions and answers printed here all cen...
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This resource warns against using pathetic fallacy and animism in the teaching of science. The author defines these terms and goes on to cite various examples of their use by college professors and other scientists. He suggests that any time a teacher uses words suggestive of human aspirations or emotions to explain the behavior of the inanimate na...
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This information is designed to belie the misconception that the capacity of air to hold water vapor is temperature dependent and that air can become saturated with water vapor. The temperature of a cloud droplet or ice crystal will be nearly the same as that of the air, so people imagine that somehow the air was to blame. But, if the other gases o...
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This Frequently asked questions (FAQ) is written in response to questions posed over the years by readers of the Bad Meteorology pages. Although the questions presented here are often ones asked by a specific person, each is chosen to characterize a group of similar questions which have been asked about the topic. The author cites four types of evi...
Article
These answers were written in response to questions from readers of the Bad Meteorology pages. Although the questions presented here are often ones asked by a specific person, each is chosen to characterize a group of similar questions which have been asked about the topic. They involve temperature conversion and energy emission. Educational levels...

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