Request data on changes in pressure and temperature with altitude in the Earth's atmosphere, preferably graphs
Editor's note: Some knowledge about atmospheric pressure changes is involved in junior high school physics courses, but there is a lack of specific explanations and instructions. This article provides a reference.
1 The existence of atmospheric pressure has become familiar to people, and relevant knowledge has become an indispensable content in primary school and junior high school textbooks. Italian scientist Torricelli first measured the value of atmospheric pressure more than 300 years ago. Torricelli invented the mercury barometer used in weather stations today.
According to Torricelli's experiment, atmospheric pressure (P) can be measured by the height of the mercury column (h mercury) in the mercury barometer, and the conversion formula is
p=ρ Mercuryghmercury
ρmercury is the density of mercury, and g is the acceleration due to gravity.
Atmospheric pressure can also be expressed in another way
or p=ρRT
Constant, T is the thermodynamic temperature of the air, and the above formula is called air The equation of state shows the relationship between the pressure, density and thermodynamic temperature of air.
Air is a mixed gas. According to the partial pressure law of mixed gases, atmospheric pressure can also be decomposed into the sum of the partial pressure of dry air (nitrogen, oxygen, argon, etc.) (pdry) and the partial pressure of water vapor (e), that is, p=pdry+e. Since the water vapor content in the air is limited (its variation range is between 0 and 4%), p dry > e. Water vapor pressure is one of the basic humidity parameters of air.
2 Based on countless measurements and a large amount of data, it is known that atmospheric pressure changes with different altitudes, different locations and different times. However, these changes are not caused by changes in air humidity, but by the earth's gravity, atmospheric circulation (the never-ending atmospheric movement around the earth is called atmospheric circulation), natural geographical conditions (latitude, land and sea distribution, topography, etc.) and It is caused by dynamic and thermal factors such as the properties of the atmosphere itself (the atmosphere has compressibility, fluidity and continuity). In other words, an increase or decrease in the amount of water vapor in the air changes the air pressure very little. When the air humidity increases, the air pressure may increase or decrease; when the humidity decreases, the air pressure may also increase or decrease. The following is a brief analysis of changes in atmospheric pressure for reference.
2.1 The change of atmospheric pressure with height
Simply put, since the atmospheric pressure is numerically equal to the weight of the vertical atmospheric column per unit area, therefore, the higher you are from the ground , the thinner the thickness of the atmosphere, the shorter the atmospheric column, and the smaller the atmospheric pressure. This had already been confirmed by Pascal and his friends in 1648. To be more precise, it is due to the effect of the earth's gravity and the compressibility of the atmosphere. As the altitude increases, the air becomes thinner and thinner, its density becomes smaller and smaller, and the temperature continues to decrease. According to the equation of state, the smaller the air density and the lower the temperature, the smaller the atmospheric pressure. In general, atmospheric pressure decreases exponentially with increasing altitude.
In actual work, the unit air pressure height difference (h) is often used to express how quickly the air pressure decreases as the altitude increases
p is the air pressure, and the unit is hectopascal, a =1/273, t represents the temperature value in degrees Celsius. It can be seen from this that when the air temperature is the same, the higher the air pressure, the smaller the altitude difference per unit air pressure, and the air pressure decreases faster with the increase of altitude; under the same air pressure, the higher the air temperature, the smaller the altitude difference per unit air pressure. The larger the difference, the slower the air pressure decreases with increasing altitude. When the altitude is low and the accuracy required is not too high, the air pressure or altitude can be calculated using the unit air pressure altitude difference. The calculation generally uses the average of the air pressure and temperature at the upper and lower points. The more accurate pressure height formula is
where z2-z1 is the height difference between the upper and lower points, tm is the average temperature between z1 and z2, pl and p2 are the heights of z1 and z2 respectively. air pressure value. The altimeter on the aircraft is modified based on the above formula and the relationship between the standard atmospheric temperature and altitude, using an empty box barometer (the air pressure scale is changed to an altitude scale).
2.2 Changes in atmospheric pressure along the horizontal direction
Usually the distribution of atmospheric pressure in the horizontal direction is uneven (so the air is subject to a net pressure from high pressure to low pressure) ——Horizontal air pressure gradient force, thus causing horizontal movement of air). By connecting the points with the same air pressure in space, a space isobaric surface is formed. The shape of the isobaric surface is undulating, convex in some places and concave in others. The air pressure in convex places is higher than the surroundings, and the air pressure in concave places is lower than the surroundings. On the sea level air pressure map, isobars (lines connecting points with equal air pressure) are used to represent air pressure distribution characteristics. The various high and low pressure areas represented by isobars are called air pressure systems. Combined with the spatial shape of the isobaric surface, the air pressure system can be divided into: high pressure (high pressure), low pressure (low pressure), high pressure ridge (ridge), low pressure trough (trough), saddle-shaped pressure field (saddle), etc. (as shown in the figure) .
In the low-pressure area, due to the friction of the earth's surface and the geostrophic deflection force generated by the rotation of the earth, the air converges in the counterclockwise direction toward the central area (so the low pressure is also called a cyclone), causing the air near the low-pressure center to Updrafts appear, transporting a large amount of water vapor and condensation nuclei near the ground and in the lower atmosphere to high altitudes; due to the expansion and cooling of the rising air, water vapor condenses to form clouds.
Therefore, low pressure areas are mostly cloudy and rainy. In the high-pressure area, the air diverges from the central area to the surroundings in a clockwise direction (high pressure is also called an anticyclone), causing downdrafts to appear near the high-pressure center. Therefore, the high-pressure area is mostly sunny.
It can be seen from the multi-year average sea level air pressure distribution: there is a low pressure area near the equator, called the equatorial low pressure belt; from the equator to the south and north respectively, the air pressure gradually increases to the north and south latitudes. Near 30°, the air pressure reaches its highest value. This high-pressure area is called the subtropical high-pressure zone. From here, continuing to high latitudes, the air pressure gradually decreases. Near 60° in the northern and southern hemispheres, the air pressure drops to its lowest value, which is called the subpolar low-pressure zone. Continuing to the south and north poles, the air pressure gradually increases, and there is a high-pressure area near the poles, called polar high pressure. This zonal distribution of air pressure is caused by factors such as the zonal distribution of solar radiation along latitude and the rotation of the Earth.
Due to the heterogeneity of the surface (latitude, sea and land distribution, topography, etc.), the differences in thermal and dynamic effects in the horizontal direction are very complicated. Therefore, a detailed analysis of the monthly mean sea level pressure distribution map can be seen It turns out that the air pressure is not strictly distributed in a zonal band, but presents many closed high and low pressure systems, which are the so-called atmospheric activity centers. Some of these atmospheric activity centers exist all year round and are called permanent atmospheric activity centers; some have significant seasonal changes and are called semi-permanent atmospheric activity centers. For example, the Mongolian high pressure, the Indian low pressure, the North Pacific subtropical high pressure and the Aleutian low pressure, etc., the changes in the relative position and intensity of these four semi-permanent and permanent atmospheric activity centers are closely related to my country's weather changes.
2.3 Diurnal and annual changes in atmospheric pressure
The general rule of diurnal changes in surface air pressure is: there is a maximum value and a second maximum value in a day; a minimum value and a The second lowest value. The highest value appears at 9 to 10 o'clock, the second highest value appears at 21 to 22 o'clock; the lowest value and the second lowest value appear at 15 to 16 o'clock and 3 to 4 o'clock respectively. The emergence of two asymmetric diurnal waves, showing a cycle every 12 hours. The occurrence of the highest and lowest values of air pressure is related to the diurnal changes in temperature: during the day, due to the heating effect of solar radiation, the air expands and rises, and then radiates around after reaching a certain height, resulting in a reduction in the mass of the air column and a decrease in ground pressure; at night, due to Due to the radiative cooling effect of the ground and the atmosphere, the air column shrinks, and the surrounding airflow converges, causing the mass of the air column to increase and the ground pressure to rise. The reasons for the occurrence of the second highest value and the second lowest value are complicated, and are generally believed to be related to the atmospheric tidal effects caused by the sun.
The annual changes in air pressure are related to the nature of the sea and land, geographical latitude, altitude and other natural geographical conditions. The highest value of air pressure in a year on the continent occurs in cold winter, and the lowest value occurs in warm summer. The annual amplitude is large, and the annual amplitude increases with increasing latitude. The annual maximum pressure value over the ocean occurs in summer, and the minimum value occurs in winter, with a small annual amplitude. The highest value of air pressure throughout the year in alpine areas occurs in summer, and the lowest value occurs in winter, and the annual amplitude is also small.
Aperiodic changes in air pressure are related to the movement and evolution of the air pressure system. In mid-to-high latitudes, due to the frequent movement and changes of high and low pressure systems, the non-periodic changes in air pressure are more obvious than in low latitudes. Drastic changes in air pressure over time are often a harbinger of drastic changes in weather. Generally speaking, a decrease in air pressure or the approach of a low-pressure system heralds the arrival of rainy weather; while the arrival of a high-pressure system usually indicates sunny weather. Therefore, it is extremely important in weather forecasting to understand the relationship between changes in air pressure over time and weather changes.
For every kilometer of elevation, the temperature drops by six degrees.
The relationship between temperature t and height h (km) is t = 18 - 6h/1000