When does winter start? Why are there two dates for the start of winter?

Arabia Weather - For some, the four seasons begin according to the Earth’s position relative to the sun, while others rely on annual temperature cycles to determine the start of the seasons, and there is a difference between the start of the season astronomically and the start of the season in meteorology.

Every year, we receive winter in meteorology on December 1, while we receive it astronomically a few weeks later with the arrival of the winter solstice, which occurs on December 20, 21, and 22. But what is the correct date for the start and end of the seasons? ?

The answer depends on the purpose of the question. The four seasons are defined in two ways: the first astronomically, which depends on the position of the Earth as it revolves around the sun, and the second, which is calculated based on meteorology, which depends on annual temperature cycles. Both divide the year into four seasons, which are: Spring Summer, fall, and winter, however, have slightly different start and end dates for each season.

Astronomical seasons - the astronomical beginning and end of seasons

People have always looked to the sky to determine the seasons of the year. In ancient times, Rome was the first to officially determine these seasons by introducing the Julian calendar. At that time, seasons began on different days than in modern times due to differences with the Gregorian calendar that is primarily used today. Currently, the beginning of each of the four seasons is determined by the equinox or solstice.

When does moderation occur?

Equinoxes occur when day and night on Earth are approximately equal. This phenomenon occurs once every six months in the spring and fall when the Earth's orbit and axial tilt coincide so that the Sun is located directly above the equator. On the day of the equinox, approximately half of the planet is illuminated, while the other half is dark. As the new season progresses, the position of the sun continues to change, and depending on which hemisphere you live in, the days will gradually become darker or brighter until the time of the solstice arrives.

When does the coup happen?

While the Solstice represents the brightest and darkest days of the year. They are also controlled by the Earth's tilt and mark the beginning of summer and winter astronomically. When the northern hemisphere is tilted toward the sun, this day marks the beginning of summer, while the southern hemisphere is tilted away from the sun at the same time, which makes this day the beginning of the astronomical winter.

But this method of measuring seasons leads to some challenges. The length of the solar year is approximately 365.2422 Earth days, which makes it impossible to synchronize any calendar perfectly with the Earth's rotation around the Sun. As a result, the seasons begin on slightly different days and times each year, making it difficult to maintain climate statistics used in agriculture, trade, and elsewhere. For this reason, weather and climate analysts have moved to using meteorology to determine the beginning and end of the seasons.

The beginning and end of chapters in meteorology

Since at least the eighteenth century, scientists have sought to find better ways to determine the beginning and end of the four seasons and the weather phenomena that accompany them, and over time this led to the emergence of the concept of weather seasons or seasons in meteorology, which correspond more precisely to annual temperatures.

The seasons in meteorology are much simpler than the astronomical seasons, as the year is divided into four seasons, each lasting exactly three months, and these seasons depend on the annual temperature cycle. Winter occurs during the three coldest months of the year, while summer occurs during the hottest months, and spring and fall represent the remaining transitional months between summer and winter.

When do the four seasons begin in meteorology?

In the Northern Hemisphere, the seasons begin as follows: on the first of March, the spring season begins, on the first of June, the summer season begins, on the first of September, the fall season begins, and finally, on the first of December, the winter season begins. . In the Southern Hemisphere, the seasons are reversed. Summer begins in December and winter begins in June.

The meteorological regularity of the seasons provides the possibility of performing complex statistical calculations necessary to predict and compare seasons with each other. "Dealing with data for whole months rather than portions of months was more economical, more convenient and more logical," climate scientist Derek Arendt told The Washington Post in 2014. "We organize our lives around months more than astronomical seasons, so our information follows this approach."

So we can say that winter and any other season have two correct dates for its beginning and end, and both calendars are correct.

Source: nationalgeographic