It is required that the data of the pressure and temperature of the earth's atmosphere change with height, and it is best to provide charts.

Editor's Note: Some knowledge about atmospheric pressure changes is involved in junior high school physics curriculum, but there is a lack of specific explanation and explanation. This paper provides a reference.

The existence of 1 atmospheric pressure has been well known, and related knowledge has become an essential content in primary and junior high school textbooks. As early as 300 years ago, Italian scientist Torricelli first measured the atmospheric pressure. So far, the mercury barometer used in weather stations was invented by Torricelli.

According to Torricelli's experiment, the atmospheric pressure (P) can be measured by the height (H Hg) of the mercury column in the mercury barometer, and its conversion formula is

P=ρ Hg gh Hg

ρ Mercury is the density of mercury, and G is the acceleration of gravity.

Atmospheric pressure can also be expressed in another way.

Or p = p = p=ρRT.

Constant, t is the thermodynamic temperature of air, and the above formula is called the equation of state of air, which represents the relationship between pressure, density and thermodynamic temperature of air.

Air is a mixed gas. According to the law of partial pressure of mixed gas, atmospheric pressure can also be decomposed into the sum of partial pressures of dry air (nitrogen, oxygen, argon, etc.) (pDry). ) and the partial pressure of water vapor (e), that is, P = PDRY+E. Because the content of water vapor in the air is limited (its range is between 0-4%), P is dry. Water vapor pressure is one of the basic parameters of air humidity.

According to numerous measurements and a lot of data, the atmospheric pressure is different at different heights, different places and different times. However, these changes are not caused by the change of air humidity, but by the dynamic and thermal factors such as the earth's gravity, atmospheric circulation (the endless atmospheric movement around the earth is called atmospheric circulation), natural geographical conditions (latitude, land and sea distribution and topography, etc.). ) and the nature of the atmosphere itself (the atmosphere has compressibility, fluidity and continuity). In other words, the increase or decrease of water vapor content in the air has little effect on the pressure. When the air humidity increases, the air pressure may increase or decrease; When the humidity decreases, the air pressure will also increase or decrease. Let's briefly analyze the changes of atmospheric pressure for your reference.

2. Variation of1atmospheric pressure with altitude

Simply put, because the atmospheric pressure is numerically equal to the weight of the vertical atmospheric column per unit area, the higher you leave the ground, the thinner the atmosphere, the shorter the atmospheric column, and the smaller the atmospheric pressure. This has long been confirmed by Pascal and his friends in 1648. More precisely, it is due to the gravity of the earth and the compressibility of the atmosphere. With the increase of height, the air is thinner and thinner, the density is smaller and smaller, and the temperature is decreasing. According to the equation of state, the lower the air density and temperature, the smaller the atmospheric pressure. Generally speaking, with the increase of height, the atmospheric pressure decreases exponentially.

In practical work, the height difference (H) of unit air pressure is often used to indicate the speed at which air pressure decreases with the increase of height.

P is the air pressure in hectopascals, a = 1/273, and t is the temperature value in degrees Celsius. It can be seen that at the same temperature, the higher the air pressure, the smaller the height difference of unit air pressure, and the faster the air pressure decreases with the increase of height; Under the same air pressure, the higher the temperature, the greater the height difference of unit air pressure, and the slower the air pressure decreases with the increase of height. When the altitude is low and the required accuracy is not too high, the altitude difference of unit air pressure can be used to calculate the air pressure or altitude. Generally, the average value of air pressure and temperature at the upper and lower points is used for calculation. A more accurate formula for pressing height is

Where z2-z 1 is the height difference between the upper and lower points, tm is the average temperature between z 1 and z2, and P 1 and p2 are the pressure values at the heights of z 1 and z2 respectively. According to the above formula and the relationship between standard atmospheric temperature and altitude, the altimeter on the plane is reformed by using the empty box barometer (the barometric scale is changed to the altitude scale).

2.2 Changes of atmospheric pressure along the horizontal direction

Usually, the distribution of atmospheric pressure in the horizontal direction is uneven (so air is subjected to a net pressure from high pressure to low pressure-horizontal pressure gradient force, which causes the horizontal movement of air). Connect all points with the same air pressure in space to form a space isobaric surface. The shape of the isobaric surface is uneven, some are convex and some are concave. The air pressure in convex places is higher than that around, and the air pressure in concave places is lower than that around. Isobars (connecting lines of points with equal air pressure) are used to represent the characteristics of air pressure distribution on the sea level pressure zoning map. Various high and low pressure areas represented by isobars are called air pressure systems. Combined with the spatial shape of isobaric surface, the air pressure system can be divided into: high pressure (high pressure), low pressure (low pressure), high pressure ridge (ridge), low pressure groove (trough), saddle-shaped air pressure field (saddle) and so on (as shown in the figure).

In the low-pressure area, due to the ground friction and the geostrophic force generated by the earth's rotation, the air converges counterclockwise to the central area (so low pressure is also called cyclone), and an updraft is formed near the low-pressure center, which transports a large amount of water vapor and condensed nodules in the lower atmosphere near the ground to the upper air; Due to the expansion and cooling of rising air, water vapor condenses into clouds. Therefore, the low-pressure area is mostly rainy weather. In the high-pressure area, the air diverges clockwise from the central area in all directions (high pressure is also called anticyclone), which makes a downward airflow near the high-pressure center, so the high-pressure area is mostly sunny.

It can be seen from the multi-year average sea level pressure distribution that there is a low pressure area near the equator, which is called the equatorial low pressure area; From the equator to the north, the air pressure gradually increases, reaching the highest value near 30 north and south latitudes. This high pressure area is called subtropical high pressure area. From this, it continues to develop to high latitudes, and the air pressure gradually decreases, reaching the lowest near 60 north and south latitudes, which is called subtropical low pressure area. Further to the north and south poles, the air pressure gradually rises, and near the polar regions is a high pressure area, which is called polar high pressure. The zonal distribution of atmospheric pressure is caused by the zonal distribution of solar radiation along latitude and the rotation of the earth.

Because of the heterogeneity of the surface (latitude, land and sea distribution and topography, etc. ), the difference of thermal and dynamic effects in the horizontal direction is very complicated. Therefore, a detailed analysis of the monthly mean sea level pressure distribution shows that the pressure is not strictly zonal, but presents many closed high and low pressure systems, which are called atmospheric activity centers. Some of these atmospheric activity centers exist all the year round and are called permanent atmospheric activity centers; Some of them have obvious seasonal changes and are called semi-permanent atmospheric activity centers. Such as Mongolia high, India low, North Pacific subtropical high and Aleutian low. The changes of the relative positions and intensities of these four semi-permanent and permanent atmospheric activity centers are closely related to the weather changes in China.

2.3 Daily and annual changes of atmospheric pressure

The general law of daily variation of ground pressure is: there is a highest value and a second highest value in a day; The lowest value and the second lowest value. The highest value appears in 9 ~ l0, and the second highest value appears in 2 1 ~ 22. The lowest value and the second lowest value appear in 15 ~ 16 and 3 ~ 4 respectively. The appearance of two asymmetric diurnal waves shows the period of 12 hours. The appearance of the highest and lowest air pressure is related to the daily variation of air temperature: during the day, due to the heating effect of solar radiation, the air expands and rises, and after reaching a certain height, it diverges around, resulting in the decrease of air column quality and ground air pressure; At night, due to the radiation cooling effect of the ground and the atmosphere, the air column shrinks and the airflow around the air converges, which increases the mass of the air column and the ground pressure. The causes of the second high value and the second low value are complicated, which are generally considered to be related to the atmospheric tides effect caused by the sun.

The annual variation of air pressure is related to natural geographical conditions such as land and sea properties, geographical latitude and altitude. The highest value of air pressure in a year on the mainland appears in cold winter, and the lowest value appears in warm summer, with a large annual amplitude, which increases with the increase of latitude. The highest pressure in the ocean in a year appears in summer, and the lowest pressure in winter, with a small annual amplitude. The highest annual air pressure in mountainous areas appears in summer and the lowest in winter, and the annual amplitude is also small.

The aperiodic change of air pressure is related to the movement and evolution of air pressure system. In the middle and high latitudes, due to the frequent movement and change of high and low pressure systems, the aperiodic change of air pressure is more obvious than that in the low latitudes. The sudden change of air pressure with time is often a sign of sudden weather change. Generally speaking, the decrease of air pressure or the approach of low-pressure system indicates rainy weather, while the arrival of high-pressure system is mostly sunny. Therefore, it is extremely important to master the relationship between the change of air pressure with time and the change of weather in weather forecast.

The temperature drops by six degrees every kilometer. The relationship between temperature t and height H (km) is t = 18-6h/ 1000.