Is the shadow of the summer solstice the longest or the shortest?

As early as thousands of years ago, our people have calculated the length of the shadow through the sundial. In addition, most of the solar terms recorded in ancient books are defined according to this law. So how does the height of the sun change in summer? This article is a simple analysis for everyone, hoping to help.

The length of the shadow of the summer solstice is determined by the height of the sun. Let's first find out where the direct sunlight from the bisector to the sun is. The summer solstice is "the day when the sun reaches the northernmost point" and the winter solstice is "the day when the sun reaches the southernmost point". Therefore, it can be concluded that at the equinox, the shadow length of an object is medium, the shortest in summer solstice and the longest in winter solstice.

The exact date is usually June 2 1 or 22/every year, when the sun reaches 90 degrees of the yellow meridian, almost directly to the Tropic of Cancer, and the sunshine time in the northern hemisphere is the longest. The arrival of this solar term means the official start of high temperature weather, and then the weather gets hotter and hotter, and there are often strong convective weather. The middle and lower reaches of the Yangtze River are in the rainy season. Here is a formula, namely [Y*D+C]-L formula: Y= two digits after the number of years, D=0.2422, L= leap year, 2 1 century C=2 1.37, and 20th century =22.20. For example, the date of summer solstice in 202 1 year = [21× 0.2422+21.37]-[21/4] = 26.45-5.25 ≈ 21. What are the climatic phenomena ① At this time, the ground is strongly heated and the air convection is strong, and thunderstorms are often easy to form in the afternoon to evening. This kind of hot thunderstorm comes and goes, and the rainfall range is small. People call it "summer rain separates the ridge", so people who travel should bring rain gear to prevent being trapped on the road. There are often cold and warm air masses in Jiangnan area, forming a trough of low pressure, which leads to rainy weather. This is not only high temperature, but also very humid, which is the legendary "sauna day". Attention should be paid to mosquito breeding and timely sterilization and pest control. ③ At this time, there are many typhoons in South China, so pay attention to strengthening flood control. Because a large part of tropical storms will be generated in the Pacific Ocean in June, although it will temporarily alleviate the heat, we should pay attention to the flood disaster.

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