How does the temperature change in a year?

The temperature of the atmosphere is called air temperature. From the long-term average, the sum of heat gain and heat loss in the ground and atmosphere systems is balanced, so the average temperature of the ground and atmosphere remains unchanged. However, at different times and in different regions, solar radiation, underlying surface properties and atmospheric conditions change, so the temperature varies with time.

Compared with solar radiation, the diurnal variation of temperature lags behind the accumulation of heat in the atmosphere. Therefore, in a day, the highest temperature generally appears at about 2 pm, which is about 2 hours later than the time when the sun's altitude angle is the largest and the solar radiation is the strongest at noon (Figure 8-4). Because the ground continuously releases long-wave radiation heat energy at night without solar radiation heat energy supplement, the heat energy stored on the ground reaches the minimum value and the temperature reaches the minimum value before sunrise.

The difference between the highest temperature and the lowest temperature in a day is called daily range. The diurnal range varies with geographical latitude, seasonal variation, surface characteristics and weather conditions. Generally speaking, the low latitude is greater than the high latitude (the average daily range of low latitude is 12℃, the middle latitude is 8℃-9℃, and the high latitude is 2℃-4℃), the summer is greater than the winter (especially in the middle latitude, but the maximum value does not appear from summer to sun, but in early summer), and the land is greater than the ocean (generally, the daily range of sea temperature is only 65433). The plateau is larger than the plain at the same latitude; The valleys and basins are larger than the upper part of the mountain (this is because the valleys and basins are not easy to dissipate heat during the day, and the cold air slides down the hillside and gathers at the bottom at night, so there is a big difference and it is particularly prone to frost).

Annual variation of temperature The time of the highest and lowest temperature in a year is later than the time of the strongest and weakest solar radiation 1-2 months respectively. The highest temperature on the mainland appears in July (August on the ocean), and the lowest temperature appears in 1 month (February on the ocean). The difference between the highest and lowest monthly average temperature in a year is called the temperature annual range. The size of tree rings also varies with latitude, ground characteristics and topography. The annual variation of temperature at different latitudes is as follows: near the equator, the temperature is the highest after the vernal equinox and autumnal equinox, the lowest in summer solstice and winter solstice, and the lowest in annual range, with high temperature all year round; With the increase of latitude, the winter and summer seasons change obviously, and the annual variation of temperature is getting bigger and bigger. For example, the annual temperature in Xisha Islands is 6℃, that in Nanjing is 26℃ and that in Hailar is 46.7℃. The ocean has a large heat capacity, so the temperature in annual range is small, and the farther inland annual range is, the greater it is; The valley or basin is larger than the upper part of the mountain; The plateau is larger than the surrounding free atmosphere, but the annual change of temperature on the low latitude plateau is particularly small, forming a spring-like scenery all year round. The lowest annual temperature in the world is Quito, the capital of Ecuador on the equator, only 0.5℃; The largest are Vilho Yansk and Oymyakon in the northeast of Siberia, with the temperature of 102℃.

The daily and annual changes of temperature are periodic changes of temperature, but the irregular movement of the atmosphere often changes this change. For example, cold air activities lead to a sharp drop in temperature, and the arrival of warm air leads to a rise in temperature again.