Why does the daily temperature change periodically?

The daily and annual changes of temperature are related to the daily and annual changes of solar radiation, which are periodic changes.

In a day, the temperature has a maximum and a minimum. After sunrise, with the enhancement of solar radiation, the temperature rises. Because it takes some time for the ground heat to transfer to the air, the maximum temperature appears at about two o'clock in the afternoon, and then the temperature gradually drops until the early morning and reaches the lowest temperature before sunrise. The difference between the highest temperature and the lowest temperature is called daily range. The daily range also varies greatly with latitude and season, which is mainly related to the height of the sun at noon. In low latitudes, the height of the sun at noon is large, and the daily variation of solar radiation is large, so the daily temperature range is also large, with an average of about 65438 02℃, while in high latitudes, it is only 3 ~ 4℃, and the height of the sun at noon in summer is larger than that in winter, so the daily temperature range in summer is also larger than that in winter. For example, in Changsha, the daily range in July is 9.0℃. In winter, 65438+ 10 is only 5.7℃. The surface properties have great influence on the daily variation of temperature. In tropical and marine areas, the daily variation of temperature is 65438 0 ~ 2℃, while in inland areas it often reaches above 65438 0.5℃ and in desert areas it often reaches 25 ~ 30℃. The daily variation of temperature is greater in the valley than in the peak, in the depression than in the mountain area, and in the dry area than in the wet area.

In a year, the annual change of temperature also has a maximum and a minimum, but the time of occurrence does not correspond to the time of the maximum and minimum of solar height (summer solstice and winter solstice), but lags behind 1 ~ 2 months. The land is less backward and the sea is more backward. The inland area is the hottest in July and the coldest in 1 month. In the ocean or coastal areas, the hottest month is August and the coldest month is February. The difference between the hottest month and the coldest month is called annual temperature difference. The annual temperature increases with the increase of latitude. The ocean is warm in winter and cool in summer, and the annual change range is smaller than that of the inland. The annual temperature is 30℃ along the coast of Tianjin and 35℃ in Hohhot.

Non-periodic variation of temperature

The aperiodic change of temperature refers to the irregular change from day to day, which is mainly caused by weather changes. Cold wave outbreak, cold air activity, front movement, cyclone activity, etc. Will cause non-periodic changes in temperature. "Dressing in disorder in February and August" is due to the large aperiodic change of temperature in the spring and autumn transition season.