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The declination of the Sun, δ ☉, is the angle between the rays of the Sun and the plane of the Earth's equator. The Earth's axial tilt (called the obliquity of the ecliptic by astronomers) is the angle between the Earth's axis and a line perpendicular to the Earth's orbit. The Earth's axial tilt changes slowly over thousands of years but its ...
For example, with an axial tilt is 23°, and at a latitude of 45°, then the summer's peak sun angle is 68° (giving sin(68°) = 93% insolation at the surface), while winter's least sun angle is 22° (giving sin(22°) = 37% insolation at the surface). Thus, the greater the axial tilt, the stronger the seasons' variations at a given latitude.
The rotational axis of Earth, for example, is the imaginary line that passes through both the North Pole and South Pole, whereas the Earth's orbital axis is the line perpendicular to the imaginary plane through which the Earth moves as it revolves around the Sun; the Earth's obliquity or axial tilt is the angle between these two lines.
] The Earth's axis of rotation tilts about 23.5 degrees, relative to the plane of Earth's orbit around the Sun. As the Earth orbits the Sun, this creates the 47° declination difference between the solstice sun paths, as well as the hemisphere-specific difference between summer and winter.
The solar zenith angle is the zenith angle of the sun, i.e., the angle between the sun’s rays and the vertical direction.It is the complement to the solar altitude or solar elevation, which is the altitude angle or elevation angle between the sun’s rays and a horizontal plane.
It is a plot of the position of the Sun at 12:00 noon at Royal Observatory, Greenwich, England (latitude 51.48°N, longitude 0.0015°W) during the year 2006. The horizontal axis is the azimuth angle in degrees (180° is facing south). The vertical axis is the altitude in degrees above the horizon.
Obliquity of the ecliptic is the term used by astronomers for the inclination of Earth's equator with respect to the ecliptic, or of Earth's rotation axis to a perpendicular to the ecliptic. It is about 23.4° and is currently decreasing 0.013 degrees (47 arcseconds) per hundred years because of planetary perturbations. [14]
There are several conventions for the solar azimuth; however, it is traditionally defined as the angle between a line due south and the shadow cast by a vertical rod on Earth. This convention states the angle is positive if the shadow is east of south and negative if it is west of south. [1] [2] For example, due east would be 90° and due west ...