The months included in vernal equinox, summer equinox, autumn equinox, direct sunlight time, latitude and winter equinox.
Every year from the vernal equinox to the autumnal equinox is the summer half year in the northern hemisphere. During this period, the sun shines directly into the northern hemisphere, and the days at all latitudes in the northern hemisphere are longer than the nights. The higher the latitude, the longer the days and the shorter the nights. Among them, from the vernal equinox to the summer solstice, the days in the northern hemisphere are getting longer and longer, and the nights are getting shorter and shorter; From the summer solstice to the autumn equinox, the days in the northern hemisphere get shorter and the nights get longer. From summer to the sun, the included angle between the end line (circle) and meridian circle is the largest (23 26 ˊ), and the daytime is the longest and shortest in all parts of the northern hemisphere. Extreme daylight appears in the Arctic Circle and its north, but the opposite is true in the southern hemisphere. The autumn equinox of each year to the spring equinox of the following year is the winter half year in the northern hemisphere. During this period, the sun shines directly in the southern hemisphere, and the night in all latitudes in the northern hemisphere is longer than the day. The higher the latitude, the longer the night and the shorter the day. Among them, from the autumnal equinox to the winter solstice, the nights in the northern hemisphere become longer and the days become shorter; From winter solstice to vernal equinox, the nights in the northern hemisphere get shorter and the days get longer. In winter to the sun, the included angle between the stop line (circle) and meridian circle is the largest (23 26 ˊ), and the night is the longest and the day is the shortest in all parts of the northern hemisphere. Extreme night occurs in the Arctic Circle and its northern region, but it is the opposite in the southern hemisphere. In the spring and autumn, the sun shines directly at the equator, and the terminal line (circle) passes through the north and south poles and coincides with a meridian coil. The world is divided into equal parts day and night, each with 12 hours.
4. blackboard writing: the change of the length of day and night in the northern hemisphere:
The vernal equinox and the autumnal equinox are equally divided day and night all over the world.
The summer solstice is long and the night is short, the day is the longest and the night is the shortest (extremely day in the Arctic Circle).
Winter solstice has short days and long nights, the shortest days and the longest nights (polar nights in the Arctic Circle).
From the above table 1, it can be seen that in the half year from the vernal equinox (March 2 1) to the autumnal equinox in the northern hemisphere, the sunrise in high latitudes with the same longitude is earlier than that in low latitudes, and gradually advances, reaching the maximum value from summer solstice (June 2 1), and then taking the distance from Changsha to Hohhot as an example, it is/kloc. The farther north the sunrise is, the later it is. When it reaches the "winter solstice" (65438+February 2 1), the sunrise time in high latitudes is delayed to the maximum, and the "winter solstice" is gradually advanced. During the period from the "autumnal equinox" to the "vernal equinox" of the following year, the sunrise time in high latitudes is later than that in low latitudes. For Changsha and Hohhot, the sunrise is delayed by about 1-0.5 minutes every 50 kilometers to the north. Because the earth always turns from west to east, it is natural that the sunrise is early in the east and late in the west on the same latitude line. For example, Chengdu and Wuhan are on the 30 north latitude line, 960 kilometers apart and 50 kilometers to the west. The sunrise in the west is about 2 minutes and 8 seconds later than that in the east all year round. However, on the 44 north latitude line, the situation is slightly different. At this latitude, Changchun and Urumqi are 3000 kilometers apart, and every 50 kilometers to the west, the sunrise will be two and a half minutes late. This further proves that the earth is indeed a sphere.
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Latitude 66? 34′70? 80? 90?
Extreme weather in the Arctic
The number of Antarctic polar nights is 165 134 186.
Extreme night days in the Arctic
The polar days in Antarctica are 160 127 179.
The extreme days in the Arctic are more than those in the Antarctic, or the extreme nights in the Arctic are less than those in the Antarctic. As we know, the polar day in the Arctic is half a year in summer. At this time, the earth is on the far side of the orbit, and its revolution speed is slow, so there are more polar days. The polar night in the Arctic is half a year in winter. At this time, the earth is on the perihelion side of the orbit, and the revolution speed is faster, so there are fewer days of extreme night.