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Spring officially begins in the Northern Hemisphere on March 20th with the Vernal Equinox as the whole world experiences an equal day and night.
To facilitate detection, meteorologists and climatologists consider March 1 to be the first day of spring, but astronomically speaking, the Earth’s equator is aligned directly with the Sun on the Vernal Equinox. In 2022, this will happen on March 20 at 11:33 am Eastern time.
The beginning of spring depends on whether you are talking about the astronomical or the meteorological start. (FOX Again)
Astronomical seasons are based on the position of the Earth relative to the Sun, as the planet makes its annual revolution around this nearest star.
The Earth is tilted about 23.5 degrees from a vertical axis, and because of this inclination, most direct sunlight is directed during our astronomical winter to the southern hemisphere and the northern hemisphere during our astronomical summer.
The Earth’s orbit around the Sun gives our planet its four seasons. (NOAA)
The two solstices and two equinoxes are simply precise moments in time when the sun is in direct alignment with three different latitudes.
Their dates can vary by a day or two each year because it takes the earth 365 days and 6 hours (365.25 days) to make a full revolution around the sun, so we have a leap year every four years.
On the winter solstice in December, the sun’s rays are positioned most directly over the tropics of Capricorn (23.5 degrees south latitude). On the summer solstice in June, most direct sun rays are aligned with the Cancer Tropic (23.5 degrees north latitude).
At the spring equinox in March and the autumn equinox in September, the equator (0 degrees latitude) is directly aligned with the sun. Therefore, everywhere on earth experiences the same 12 hours day and night, as the sun rises in the east and sets in the west.
In summer the sun rises in the northeastern sky and sets in the northwestern sky, which provides for long days and short nights. The sun reaches its highest point in the northern hemisphere at noon (approximately 13:00 local time due to solar time) on the summer solstice. This ensures the direct solar radiation of the year, which results in more warming of the earth’s surface and hence warmer temperatures.
In winter, the sunrise is in the southeastern sky and the sunset is in the southwestern sky – a much shorter way across the sky of the northern hemisphere – so the days are short and the nights are long. The midday sun angle is the lowest and farthest south in the sky on winter solstice. That is, we have the least direct solar radiation of the year on the first day of winter, which results in colder temperatures because there is less warming of the earth’s surface.
Interestingly, the Earth’s orbit around the Sun is elliptical (not perfectly circular), so it is actually closest to the sun in January (perihelion) during the northern hemisphere winter farthest from the sun in July (aphelion) during the northern hemisphere summer.
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