What is the dog days in 2024?
Debut in 2024: July 2024 15-July 24, 2024;
Mid-range in 2024: July 25, 2024-August 202413;
Terminal voltage in 2024: August 2024 14-August 23, 2024.
Among them, the first day of 2023 10, the middle day is 20 days, and the last day 10 * * 40 days.
Why is the mid-range sometimes 10 days and sometimes 20 days?
Starting from the summer solstice, according to the date of trunk, the third Geng day is the first, the fourth Geng day is the middle, and the 1 th Geng day after beginning of autumn is the last. The interval of each Geng day is 10 day, the time from initial lodging to intermediate lodging is 10 day, and the final lodging is 10 day. Summer may be 10 days, or 20 days, because when there are four Geng days between the summer solstice and the beginning of autumn, it is 10 days, and when there are five Geng days, it is 20 days.
Why is it the hottest in dog days?
It is not only supported by climatic data and folk experience, but also has theoretical basis in astronomy and meteorology.
Every summer solstice, the sun shines directly on the Tropic of Cancer. At this time, the northern hemisphere gets the most sunlight and the solar altitude angle is the largest. Take Beijing as an example. At noon on the day of summer solstice, the height of the sun is 73.5 degrees, and the sun is close to the ground. At this time, the thickness of the atmosphere through which sunlight passes is the smallest, and the amount of light and heat absorbed, scattered and reflected by the atmosphere is also small, so more people reach the ground, which is beneficial to the temperature rise of the ground.
In addition, in summer, the day is longer than the night, the day is longer and the sunshine time is longer. The heat absorbed by the ground is far greater than the divergence, which makes the heat gathered on the ground increase day by day and the temperature continues to rise. Dog days are the third watch from summer to the future, and the accumulation of ground heat reaches its peak in dog days, which is the basic reason for the hottest in dog days.
From the meteorological point of view, there is much rain in summer and the air humidity is high, and the heat capacity of water is much larger than that of dry air. In addition, the low average wind speed and the low air pressure before the thunderstorm are also important reasons for the sultry weather in dog days.
Of course, in more days in July and August, the weather situation in many parts of China is controlled or influenced by the subtropical high. The downward flow of high pressure inside makes the weather clear and partly cloudy, which is conducive to the warming of sunlight and ground radiation, so it is still "dry and hot weather" in dog days.