Characteristics of Shanghai in Spring, Summer, Autumn and Winter

Students like to take part in some seasonal activities: spring outing in the suburbs, swimming in rivers and lakes in summer, hiking and mountain climbing in autumn, watching red leaves in winter, skating, skiing and making a snowman. Leng Xia is hot in winter, warm in spring and cool in autumn. People in most parts of our country have personal feelings about the changes of these four seasons. However, when is spring, when is summer, when is autumn and when is winter? I'm afraid many people can't say this clearly.

I talked about this knowledge in geography class: because the earth revolves around the sun obliquely, the sun is very high in some areas of the earth all year round; In some areas, the sun always rotates on the horizon in a year; There are also some areas, sometimes directly exposed to the sun, sometimes obliquely exposed to the sun, that is to say, these areas receive different sunlight and heat in different seasons. According to the different acceptance of solar light and heat in different regions, the earth is divided into tropical zone, north-south temperate zone and south-north cold zone; In temperate zones, there are also four seasons of climate change. Although in astronomy, there are solar terms such as spring equinox, summer solstice, autumn equinox and winter solstice all over the world, in fact, not all regions can divide a year into four seasons. Cold areas are very cold all year round, and there is no heat; Tropical areas are hot all year round, with no spring and autumn and no winter; Only temperate regions can be divided into four seasons: spring, summer, autumn and winter. When the direct point of the sun is in the northern hemisphere, the temperate zone in the northern hemisphere enters summer and the temperate zone in the southern hemisphere begins winter; When the direct point of the sun is in the southern hemisphere, the temperate zone in the southern hemisphere is summer, while the temperate zone in the northern hemisphere is only cold winter; When the sun shines directly near the equator, it is spring and autumn in the temperate regions of the northern and southern hemispheres. Most of China is located in the north temperate zone and the north subtropical zone, with intense heat in winter and distinct seasons.

So, how are the four seasons of a year divided?

There are many ways to divide the four seasons:

In ancient China, beginning of spring, Changxia, beginning of autumn and beginning of winter were four seasons.

On the calendar published in China, next to the date of a year, there is also a lunar calendar, also called the summer calendar, which is what we usually call the "lunar calendar". According to China folk customs, the lunar month is divided into four seasons: January to March is spring, April to June is summer, July to September is autumn, and October to December is winter. Children are looking forward to "Year", which refers to the first day of the first lunar month; This day is not only the first day of the year, but also the beginning of spring in the division of lunar seasons, so it is called the Spring Festival.

Astronomically, the spring equinox, summer solstice, autumn equinox and winter solstice are four seasons.

Meteorologically, March to May is usually spring, June to August is summer, September to165438+1October is autumn, and June to February is winter.

If you think about it carefully, you will find that there is a problem in the above four seasons division methods: no matter where you are, you will enter the same season on the same day, which is very different from the actual climate conditions in various regions. For example, according to the above standards, March should be spring. At this time, the swallow grass in Jiangnan is long, pink and green, and the spring is really strong; Heilongjiang province is still freezing cold and snowy; Moreover, it is already a hot summer day in Hainan Island, so you can wear light clothes.

Seasonal changes are closely related to people's lives and industrial and agricultural production. Can we formulate a standard for dividing the four seasons in line with the changes of natural scenery?

In order to reflect the phenological phenomenon of seasonal changes in a region as truly as possible, the meteorological department divides four seasons with the five-day average temperature (referred to as average temperature) as the index: the average temperature is set below 10℃, and the colder period is called winter; The season when the average temperature is stable above 22℃ and people can wear light clothes is called summer. The average temperature is between 10℃ and 22℃, and the warm seasons are spring and autumn. This division method accords with the actual climate situation in China, especially the changes of natural scenery in eastern China. For example, in late March or the end of March, when the average temperature in Beijing rises to around 10℃, it enters spring. At this time, the peach blossoms and willow buds are green, and it is indeed full of spring; 1 1 year1late October, in Jiangsu and Zhejiang provinces, the leaves of plane trees fell, and the scenery was bleak. The average temperature was just around 10℃, and winter began. Comparing the existence and length of four seasons in different regions of China with this index, we can clearly see the differences of seasonal changes in different regions of China.

-from Lin? China Children's Publishing House "Spring, Summer, Autumn and Winter in China"