Bloom is warm in spring, and it makes no difference in the north. Why is there no such thing as flowers everywhere in the south?

Because the climate difference between the north and the south is too great, when bloom in the south is warm in spring, it is still cold in the north.

North-South boundary, traditional North-South boundary, 1 month 0 degree isotherm, 800mm isoprecipitation line, paddy field and dry land distribution boundary, rice and wheat planting boundary, subtropical and warm temperate zone boundary, subtropical evergreen broad-leaved forest and temperate deciduous broad-leaved forest boundary, humid and semi-humid boundary, subtropical monsoon climate and temperate monsoon climate boundary.

In most areas north of Qinhuai, rivers and lakes will freeze in winter. When winter comes and the north wind whistles, most trees will lose their leaves, and the leaves that do not lose their leaves are mostly needle-shaped, which is called conifers.

Because the annual precipitation in the northern region is less, and the precipitation is mostly concentrated in summer, the river water volume is small and the water level changes greatly. The flood season is only formed in summer, the time is relatively short, and the river sediment concentration is relatively large. In the south of Qinhuai, on the other hand, there is no ice in winter, no deciduous trees and evergreen seasons. The river has large water volume, small water level change, long flood season and small river sediment concentration.

Extended data

natural boundary

In fact, the natural dividing line between north and south in China is the climate dividing line first. As far as the hot zone is concerned, it is the dividing line between the northern warm temperate zone and the southern subtropical zone; In the division of water, it is the dividing line between the arid and semi-humid climate in the north and the humid climate in the south; In the division of rainy season and dry season, it is the dividing line between spring drought and summer rain climate in the north and spring rain, plum rain and summer drought climate in the south.

However, this transition and change is completed through a fairly wide belt. We can't see any changes in climate, agriculture, natural landscape, etc. on both sides of the Huaihe River, which are more than ten or twenty kilometers apart. In fact, because the Huaihe River area is mainly a plain area, the cold and warm air flow between the north and the south is unimpeded, and it is really impossible to produce a clear north-south dividing line.

Take "orange crossing Huaihe River, turning north into bitter orange" as an example. Due to the strong cold air in the central and southern parts of eastern China in winter, it often brings fatal low temperature to citrus. Therefore, even on the banks of the Yangtze River south of Huaihe River, except for some favorable areas, citrus cultivation generally has no economic value.

The Qinling Mountains to the west of the north-south boundary block the cold air in the north in winter, so Lingnan is a typical subtropical zone (it can grow citrus and other subtropical index plants that can't grow on both sides of Huaihe River at the same latitude) when it is a typical warm temperate zone to the north of the ridge. However, the Qinling boundary is not a line.

Because the southern slope of Qinling Mountain is subtropical only at an altitude of 1000 meters, and the width between the contour lines of the two slopes of Qinling Mountain, that is, the width of the boundary zone, is about 90- 1 10 km. Moreover, in history, the north-south boundary zone moved north and south with climate change. If global warming continues, the subtropical northern boundary may even move northward to the middle and lower reaches of the Yellow River in the future.

Meridian and meridian pass through two poles and are perpendicular to the equator, which is called meridian coil or meridian, also called meridian. Since all the meridians intersect at the north and south poles and are perpendicular to the latitude, any meridian represents the north-south direction on the earth.

The earth is a sphere with countless meridians. Therefore, in order to facilitate the calculation, it is decided that the meridian passing through Greenwich Observatory in the eastern suburb of London, England, is the zero meridian, also known as the prime meridian. In order to make Britain, France and other countries on the African continent belong to the same hemisphere, the eastern and western hemispheres are divided by east longitude 160 and west longitude 20.

The longitude of a point on the earth is the angle between the meridian plane where the point is located and the prime meridian plane. This included angle is equivalent to the angle of the equatorial arc between the two planes in the center of the earth. The east of the prime meridian is called east longitude, which is represented by "e"; The Western Classics is called the Western Classics and is represented by "W". The circumference of the earth is 360, so the east and west meridians are 180 respectively.