The area where the air pressure changes the most in a year.

The air pressure has been changing. Under normal circumstances, the air pressure rises every morning and falls in the afternoon; The air pressure is the highest in winter and the lowest in summer. But sometimes, for example, under the influence of a cold wave, the air pressure will rise quickly, but as soon as the cold air passes, the air pressure will gradually drop.

Atmospheric pressure is related to altitude, temperature and season. The air pressure decreases with the increase of altitude, and the higher the altitude, the smaller the air pressure; It is also related to temperature and season. The air pressure in sunny days is higher than that in cloudy days, and that in winter is higher than that in summer.

What are the characteristics of the law of air pressure change?

Like other meteorological elements, atmospheric pressure changes with time. This change includes both periodic change (daily change and annual change) and non-periodic change. The latter reflects the movement and evolution of pneumatic system. When making weather forecast, we should not only consider the periodic daily and annual changes of air pressure, but also consider the non-periodic changes of air pressure. It is necessary to master the daily and annual variation of air pressure, which is obtained through the statistical average of a large number of long-term observation data.

Diurnal variation of air pressure

Generally speaking, in the daily variation of air pressure, there are two high-value periods and two low-value periods in a day. The highest and lowest values appear in the local area ((local time, the same below) 9? 10 hour and 15 ~ 16 hour; The second highest value and the second lowest value appear in 2 1 ~ 22 hours and 3? Four o'clock.

The appearance of the highest and lowest air pressure is related to the daily variation of temperature. In the daily variation of air pressure, there are several different vibration periods, the most significant of which are the 24-hour period affected by temperature and the 12-hour period related to atmospheric tides. In addition, there are short periods of 8 hours and 6 hours, and the vibration results of several different periods are combined to make the daily change of air pressure fluctuate twice every 24 hours.

Annual variation of air pressure

According to the air pressure data observed in various places for many years, the monthly average air pressure can be calculated and drawn into the annual variation curve of air pressure. The most common annual variation curves of air pressure can be summarized into the following three basic types:

Continental type: the highest pressure appears in winter and the lowest pressure appears in summer.

Ocean type: Contrary to continental type, the highest atmospheric pressure appears in summer and the lowest in winter, and the atmospheric pressure is less than continental type throughout the year.

The annual variation of these two air pressures is caused by the difference between the cold and warm temperatures of the land and the ocean. In winter, the mainland is colder than the ocean. On the colder surface, the atmospheric column shrinks, and there is air flowing over the ocean, which increases the mass of the atmospheric column per unit area on the land, but on the ocean surface, it is the opposite, so the atmospheric pressure on the mainland is high and the atmospheric pressure on the ocean surface is low in winter. In summer, the situation is just the opposite.

Alpine type: the highest air pressure in Lushan area appears in warm season and the lowest in winter. The annual variation of this air pressure seems to be similar to that of the ocean type, but they are formed for different reasons. In the warm season, due to the heating of the atmosphere and the expansion of the air column, the mass of the air column above the ground in Lushan area increases, so the air pressure increases. In the cold season, due to the cooling of the atmosphere and the contraction of the air column, the mass of the air column above the ground in Lushan area is reduced, so the air pressure is reduced.

The annual variation of air pressure increases with the increase of latitude, while the annual variation of offshore air pressure is small, and the deeper the inland, the greater the annual variation. The annual amplitude of land pressure in People's Republic of China (PRC) varies greatly from place to place, and the coastal areas south of Fujian are all around 16hPa. The eastern coast and southeast are around 2 1.2hPa, and the North China Plain, Central China, Central South China and Sichuan Basin are all above 24hPa. As far as the northeast and northwest are concerned, the annual amplitude in the hilly area of southwest is generally below 13.2hPa, while that in Lhasa is as low as 5.3hPa.

The annual variation of air pressure in the upper atmosphere is just opposite to that on the ground. The maximum air pressure appears in summer and the minimum air pressure appears in winter. This is because the whole troposphere heats up in summer and cools down in winter. It can be concluded that the air pressure in summer is lower than that in winter with the decrease of height.

What factors are related to the change of air pressure?

The air pressure varies with the height of the atmosphere, because the air itself has weight, and the earth has a gravitational effect on matter. The closer the center distance is, the greater the gravity is. Therefore, the closer to the site, the greater the atmospheric density, and the closer to the high altitude.

Air pressure also changes with the change of temperature. This is because gas expands with heat and contracts with cold. When the temperature is low, the gas contracts, the density increases and the pressure increases. On the contrary, when the air temperature is high, the gas expands and the density decreases, so the air pressure also decreases.

Under normal circumstances, the ground continuously radiates long waves to the atmosphere effectively, and the atmosphere is also constantly radiating back to the ground. On sunny days, the heat on the ground can be transported to the outside through the effective radiation and upward divergence of the convective gas layer. On cloudy days, clouds reduce the outward divergence of troposphere atmosphere. The heat preservation effect of clouds on the surface and troposphere is called "greenhouse effect". In this way, the atmospheric expansion in cloudy areas is more intense, which leads to the lateral outward diffusion of the atmosphere in cloudy areas and reduces the density of air. At the same time, the atmospheric humidity in cloudy areas is high, which also reduces the density of the atmosphere. Due to these two factors, the air pressure on cloudy days is lower than that on sunny days.

The change of air pressure has an impact on the human body and will bring three kinds of physical discomfort.

With the change of weather patterns such as storms, the change of air pressure will have a certain impact on the body, and some people are particularly sensitive to this. The American "Mother Nature Website" recently summarized three major impacts of air pressure change on human body.

1. Headache/migraine. Researchers at Japan Independent Medical University asked migraine sufferers to record the occurrence of headache in a year, and then compared these diaries with the changes of air pressure recorded by nearby weather stations, and found that low air pressure was directly related to the onset and duration of migraine. Researchers point out that low air pressure can lead to a pressure difference between the atmosphere and the sinuses, which can lead to headaches or migraines. When the sinuses are congested or blocked, the problem will be aggravated.

2. Joint pain. Researchers at Tufts New England Medical Center in England investigated 200 patients with knee osteoarthritis and found that there was a relationship between the changes of air pressure and ambient temperature and the degree of knee pain. This may be because the air pressure affects the viscosity of the liquid connecting the joint capsule, and may also trigger the painful reaction of the joint nerve endings. In either case, some people will feel joint pain when the storm comes.

3. Blood pressure changes. Blood flows through the body through the pressure generated by the heart, which is affected by the surrounding air pressure. Biometeorologists believe that when the air pressure drops, the blood pressure will also drop. For some people, this may mean that they feel dizzy or have blurred vision. Blood vessels will respond to sudden changes in environmental humidity, atmospheric pressure, cloud thickness or wind and cold, and weather-related blood pressure changes are more common in people over 65 years old.

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