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Overcast Mehamn
Overcast or overcast weather, as defined by the World Meteorological Organization, is the meteorological condition of clouds obscuring at least 95% of the sky. However, the total cloud cover must not be entirely due to obscuring phenomena near the surface, such as fog. Overcast, written as "OVC" in the METAR observation, is reported when the cloud cover is observed to equal eight oktas (eighths). An overcast sky may be explicitly identified as thin (mostly transparent), but otherwise considered opaque—which always constitutes a ceiling in aviation meteorology. Sometimes clouds can be of different colors such as black or white, but overcast usually refers to darker skies.''Oxford English Dictionary'', 3rd ed. (website), s.v. “overcast," 2a and 2b. http://www.oed.com/view/Entry/134377#eid32922408 (Accessed September 7, 2016). In some cases, it can be characterized by almost zero distinction of borders of clouds. Or the sky may be covered by a single type of cloud, such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seasonal Affective Disorder
Seasonal affective disorder (SAD) is a mood disorder subset in which people who typically have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year. It is commonly, but not always, associated with the reductions or increases in total daily sunlight hours that occur during the winter or summer. Common symptoms include sleeping too much, having little to no energy, and overeating. The condition in the summer can include heightened anxiety.Seasonal affective disorder (SAD): Symptoms MayoClinic.com (September 22, 2011). Retrieved on March 24, 2013. However, there are significant differences in the duration, severity, and symptoms of each individual's experience of SAD. For instance, in a fifth of patients, the disor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photon Diffusion
Photon diffusion is a situation where photons travel through a material without being absorbed, but rather undergoing repeated scattering events which change the direction of their path. The path of any given photon is then effectively a random walk. A large ensemble of such photons can be said to exhibit diffusion in the material, and can be described with a diffusion equation. Astrophysics In astrophysics, photon diffusion occurs inside a stellar atmosphere. To describe this phenomenon, one should develop the transfer equation in moments and use the Eddington approximation to radiative transfer (i.e. the diffusion approximation). In 3D the results are two equations for the photon energy flux: :\vec F = -\frac\vec \nabla U, :\vec \nabla \cdot \vec F = 0, where \sigma is the opacity. By substituting the first equation into the second, one obtains the diffusion equation for the photon energy density: :\nabla^2 U -\frac\vec \nabla U \cdot \vec \nabla \sigma=0. Medical science In me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hard And Soft Light
Hard means something that is difficult to do. It may also refer to: * Hardness, resistance of physical materials to deformation or fracture * Hard water, water with high mineral content Arts and entertainment * ''Hard'' (TV series), a French TV series * Hard (band), a Hungarian hard rock supergroup * Hard (music festival), in the U.S. Albums * ''Hard'' (EP), Goodbye Mr Mackenzie, 1993 * ''Hard'' (Brainpower album), 2008 * ''Hard'' (Gang of Four album), 1983 * ''Hard'' (Jagged Edge album), 2003 * ''Hard'' (Shinee album), 2023, and its title track * ''Hard'', a 2017 EP from the band The Neighbourhood Songs * "Hard" (Rihanna song), 2009 * "Hard" (Sophie song), 2014 * "Hard", a song by Royce da 5'9" from the 2016 album '' Layers'' * "Hard", a song by Why Don't We from the 2018 album '' 8 Letters'' * "Hard", a song by Poppy from the 2023 album ''Zig'' Places * Hard, Austria * Hard (Zürich), Switzerland Other uses * Hard (surname) * Hard architecture, impersonal win ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
June Gloom
June Gloom is a mainly Southern California term for a weather pattern that results in cloud cover, cloudy, overcast skies with cool temperatures during the late spring and early summer. While the marine layer is most common in the month of June, it can occur in surrounding months, giving rise to other colloquialisms, such as Graypril, May Gray, No-Sky July, and Summer Bummer and Junuary in the Puget Sound region. Low-altitude stratus clouds form over the cool water of the California Current, and spread overnight into the coastal regions of California. The overcast skies often are accompanied by fog and drizzle, though usually not rain. June Gloom usually clears up between mid-morning and early afternoon, depending on the strength of the marine layer and the distance of the location from the Pacific Ocean, and gives way to sunny skies. May and June together are usually the cloudiest months in coastal California. June Gloom is stronger in years associated with a La Niña, and wea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gloom
Gloom is a low level of light which is so dim that there are physiological and psychological effects. Human vision at this level becomes monochrome and has lessened clarity. Optical and psychological effects Light conditions may be considered gloomy when the level of light in an environment is too low for the proper function of cone cells, and colour vision is lost. In a study by Rothwell and Campbell, light levels described as "gloomy" fell between 28 and 3.6 cd/m2. Low light and lack of color of this sort may be associated with depression and lethargy. This association was made as far back as the 2nd century by the ancient Greek physician, Aretaeus of Cappadocia, who said, "Lethargics are to be laid in the light and exposed to the rays of the sun, for the disease is gloom." Also, some studies have found weaker electrical activity in the retinas of depressed people, which gave the individuals studied poor visual contrast, meaning that they saw the world in grayer hue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuser (optics)
In optics, a diffuser (also called a light diffuser or optical diffuser) is any material that diffuses or scatters light in some manner to transmit soft light. Diffused light can be easily obtained by reflecting light from a white surface, while more compact diffusers may use translucent material, including ground glass, teflon, opal glass, and greyed glass. Types Perfect reflecting diffuser A perfect (reflecting) diffuser (PRD) is a theoretical perfectly white surface with Lambertian reflectance (its brightness appears the same from any angle of view). It does not absorb light, giving back 100% of the light it receives. Reflective diffusers can be easily characterised by scatterometers.{{cite web, url=http://www.zebraoptical.com/roughnessviascatterometry.html, title=Page Title, website=www.zebraoptical.com Diffractive diffuser/homogenizer A diffractive diffuser is a kind of diffractive optical element (DOE) that exploits the principles of diffraction and refraction. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Light Scattering By Particles
Light scattering by particles is the process by which small particles (e.g. ice crystals, dust, atmospheric particulates, cosmic dust, and blood cells) light scattering, scatter light causing optical phenomena such as the Rayleigh scattering, blue color of the sky, and halo (optical phenomenon), halos. Maxwell's equations are the basis of theoretical and computational methods describing light scattering, but since exact solutions to Maxwell's equations are only known for selected particle geometries (such as spherical), light scattering by particles is a branch of computational electromagnetics dealing with electromagnetic radiation scattering and absorption by particles. In case of shape, geometries for which analytical solutions are known (such as spheres, cluster of spheres, infinite cylinder (geometry), cylinders), the solutions are typically calculated in terms of series (mathematics)#Infinite series, infinite series. In case of more complex geometries and for inhomogeneous p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forward Scatter
Forward scattering is the deflection of waves by small angles so that they continue to move in close to the same direction as before the scattering. It can occur with all types of waves, for instance light, ultraviolet radiation, X-rays as well as matter waves such as electrons, neutrons and even water waves. It can be due to diffraction, refraction, and low angle reflection. It almost always occurs when the wavelength of the radiation used is small relative to the features which lead to the scattering. Forward scatter is essentially the reverse of backscatter. Many different examples exist, and there are very large fields where forward scattering dominates, in particular for electron diffraction and electron microscopy, X-ray diffraction and neutron diffraction. In these the relevant waves are transmitted through the samples. One case where there is forward scattering in a reflection geometry is reflection high-energy electron diffraction. General description Whenever waves ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffuse Reflection
Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection. An ''ideal'' diffuse reflecting surface is said to exhibit Lambertian reflection, meaning that there is equal luminance when viewed from all directions lying in the half-space adjacent to the surface. A surface built from a non-absorbing powder such as plaster, or from fibers such as paper, or from a polycrystalline material such as white marble, reflects light diffusely with great efficiency. Many common materials exhibit a mixture of specular and diffuse reflection. The visibility of objects, excluding light-emitting ones, is primarily caused by diffuse reflection of light: it is diffusely-scattered light that forms the image of the object in an observer's eye over a wide range of angles of the observer with respect to the object. Mechanism Di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratus Cloud
Stratus clouds are low-level clouds characterized by horizontal layering with a uniform base, as opposed to convective or cumuliform clouds formed by rising thermals. The term ''stratus'' describes flat, hazy, featureless clouds at low altitudes varying in color from dark gray to nearly white. The word ''stratus'' comes from the Latin prefix ''Strato-'', meaning "layer" or "sheet". Stratus clouds may produce a light drizzle or a small amount of snow. These clouds are essentially above-ground fog formed either through the lifting of morning fog or through cold air moving at low altitudes. Some call these clouds "high fog" for their fog-like form. Formation Stratus clouds form when weak vertical currents lift a layer of air off the ground and it depressurizes, following the lapse rate. This causes the relative humidity to increase due to the adiabatic cooling. This occurs in environments where atmospheric ''stability'' is abundant. Description Stratus clouds look like ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Meteorological Organization
The World Meteorological Organization (WMO) is a List of specialized agencies of the United Nations, specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the International Meteorological Organization (IMO), a nongovernmental organization founded in 1873 as a forum for exchanging weather data and research. Proposals to reform the status and structure of the IMO culminated in the World Meteorological Convention of 1947, which formally established the World Meteorological Organization. The Convention entered into force on 23 March 1950, and the following year the WMO began operations as an intergovernmental organization within the UN system. The WMO is made up of 193 countries and territories, and facilitates the "free and unrestricted" exchange of data, information, and research between the respective meteorological and hydrological institutions of its m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
