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Sunset colors are typically more brilliant than sunrise colors, because the evening air contains more particles than morning air. [2] [3] [5] [8] Sometimes just before sunrise or after sunset a green flash can be seen. [9]
Calculate the sunset time, which is the solar noon time plus the sunset hour angle in degree divided by 15; Use the sunset time as input to the solar geometry routine to get the solar azimuth angle at sunset. An interesting feature in the figure on the right is apparent hemispheric symmetry in regions where daily sunrise and sunset actually occur.
[9] [10] [12] [15] Ash from volcanic eruptions, trapped within the troposphere, tends to mute sunset and sunrise colors, while volcanic ejecta that is instead lofted into the stratosphere (as thin clouds of tiny sulfuric acid droplets), can yield beautiful post-sunset colors called afterglows and pre-sunrise glows.
The color temperature of daylight varies with the time of day. It tends to be around 2,000 K shortly after sunrise or before sunset, around 3,500 K during "golden hour", and around 5,500 K at midday. The color temperature can also change significantly with altitude, latitude, season, and weather conditions.
At sunrise or sunset, tangentially incident solar rays illuminate clouds with orange to red hues. The visible spectrum, approximately 380 to 740 nanometers (nm), [1] shows the atmospheric water absorption band and the solar Fraunhofer lines. The blue sky spectrum contains light at all visible wavelengths with a broad maximum around 450–485 nm ...
During twilight (the duration after sunset or before sunrise until or since, respectively, the full darkness of night), the situation is more complicated, and a further differentiation is required. Twilight (both dusk and dawn ) is divided into three 6° segments that mark the Sun's position below the horizon.
The small particles in the expanding exhaust plume or "cloud" diffract sunlight and produce the rose, blue, green and orange colors—much like a dispersive prism can be used to break light up into its constituent spectral colors (the colors of the rainbow) – thereby making the twilight phenomenon all the more spectacular. [1]
Strictly speaking, alpenglow refers to indirect sunlight reflected or diffracted by the atmosphere after sunset or before sunrise. This diffuse illumination creates soft shadows in addition to the reddish color. The term is also used informally to include direct illumination by the reddish light of the rising or setting sun, with sharply ...