气压是一个困难的概念。看不见的东西怎么会有质量和重量？空气具有质量，因为它由具有质量的气体混合物组成。加上构成干燥空气（氧气，氮气，二氧化碳，氢气等）的所有这些气体的重量，你就可以得到干燥空气的重量。低压系统中心的压力低于周围区域的空气压力。风吹向低压区域，导致大气中的空气上升。上升的空气中的水蒸气凝结成云，在许多情况下，形成降水。由于科里奥利效应是地球自转的结果，低压系统中的风在北半球逆时针循环，在南半球顺时针循环。低压系统会产生不稳定的天气和风暴，如旋风，飓风和台风。作为一般经验法则，低压的压力约为1000毫巴（29.54英寸汞柱）。截至2016年，1979年10月12日太平洋上台风尖的眼中，地球上记录的最低压力为870 mb（25.69 inHg）。干燥空气的分子量或摩尔质量为28.97克/摩尔。 。虽然这不是很多，但典型的气团由大量的空气分子组成。因此，当所有分子的质量加在一起时，您可以开始看到空气如何具有相当大的重量。气压计用于以大气压或milibars为单位测量大气压。最古老的气压计是水银气压计。当气压计在气压计的玻璃管中上升或下降时，该仪器测量汞。由于大气压力基本上是储层上方大气中的空气重量，因此气压计中的汞水平将继续变化，直到玻璃管中的汞重量恰好等于储层上方的空气重量。一旦两者停止移动并保持平衡，则通过“读取”垂直柱中汞高度处的值来记录压力。那么分子和气压之间的关系是什么？如果一个区域上方的空气分子数增加，则有更多分子在该区域施加压力并且其总大气压力增加。这就是我们所说的高压。同样，如果区域上方的空气分子较少，则大气压力会降低。这被称为低压。如果汞的重量小于大气压，则玻璃管中的汞含量将升高（高压）。在高压区域，空气向地表下沉的速度比流向周围区域的速度快。由于表面上方的空气分子数量增加，因此有更多的分子在该表面上施加力。随着储层上方空气重量的增加，汞含量上升到更高的水平。整个地球的气压不均匀。它的范围从980到1050毫巴，随海拔高度而变化。海拔越高，气压越低。这是因为空气分子的数量在较高海拔处降低，从而降低了空气密度和空气压力。空气密度最大的海平面气压最高。如果汞的重量大于大气压，则汞含量将下降（低压）。在低压区域，空气从地球表面上升得比从周围区域流入的空气更快。由于该区域上方的空气分子数量减少，因此在该表面上施加力的分子较少。随着储层上方空气重量的减少，汞含量降至较低水平。其他类型的气压计包括无液气压计和数字气压计。 Aneroid气压计不含汞或任何其他液体，但它们具有密封且气密的金属腔。腔室响应压力变化而膨胀或收缩，并且表盘上的指针用于指示压力读数。现代气压计是数字式的，能够准确，快速地测量大气压力。这些电子仪器在显示屏上显示当前的大气压读数。
英国考文垂大学气象学Essay代写：气压基础知识
Air pressure is a difficult concept. How can something invisible have mass and weight? Air has mass because it is made up of a mixture of gases that have mass. Add up the weight of all these gases that compose dry air (oxygen, nitrogen, carbon dioxide, hydrogen, and others) and you get the weight of dry air. The pressure at the center of a low pressure system is lower than air in the surrounding area. Winds blow toward the area of low pressure causing air in the atmosphere to rise. Water vapor in the rising air condenses forming clouds and, in many cases, precipitation. Due to the Coriolis Effect, a result of the Earth’s rotation, winds in a low pressure system circulate counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Low pressure systems can produce unstable weather and storms such as cyclones, hurricanes, and typhoons. As a general rule of thumb, lows have a pressure of around 1000 millibars (29.54 inches of mercury). As of 2016, the lowest pressure ever recorded on Earth was 870 mb (25.69 inHg) in the eye of Typhoon Tip over the Pacific Ocean on October 12, 1979. The molecular weight, or molar mass, of dry air is 28.97 grams per mole. While that isn’t very much, a typical air mass is made up of an incredibly large number of air molecules. As such, you can begin to see how air can have considerable weight when the masses of all the molecules are added together. A barometer is used to measure atmospheric pressure in units called atmospheres or milibars. The oldest type of barometer is the mercury barometer. This instrument measures mercury as it rises or lowers in the glass tube of the barometer. Since atmospheric pressure is basically the weight of air in the atmosphere above the reservoir, the level of mercury in the barometer will continue to change until the weight of mercury in the glass tube is exactly equal to the weight of air above the reservoir. Once the two have stopped moving and are balanced, the pressure is recorded by “reading” the value at the mercury’s height in the vertical column. So what’s the connection between molecules and air pressure? If the number of air molecules above an area increases, there are more molecules to exert pressure on that area and its total atmospheric pressure increases. This is what we call high pressure. Likewise, if there are less air molecules above an area, the atmospheric pressure decreases. This is known as low pressure. If the weight of mercury is less than the atmospheric pressure, the mercury level in the glass tube will rise (high pressure). In areas of high pressure, air is sinking toward the surface of the earth more quickly than it can flow out to surrounding areas. Since the number of air molecules above the surface increases, there are more molecules to exert a force on that surface. With an increased weight of air above the reservoir, the mercury level rises to a higher level. Air pressure isn’t uniform across the Earth. It ranges from 980 to 1050 millibars and changes with altitude. The higher the altitude, the lower the air pressure. This is because the number of air molecules decreases at higher altitudes, thus decreasing air density and air pressure. Air pressure is highest at sea level, where air density is greatest. If the weight of mercury is greater than the atmospheric pressure, the mercury level will fall (low pressure). In areas of low pressure, air is rising away from the surface of the Earth more quickly than it can be replaced by air flowing in from surrounding areas. Since the number of air molecules above the area decreases, there are less molecules to exert a force on that surface. With a reduced weight of air above the reservoir, the mercury level drops to a lower level. Other types of barometers include aneroid and digital barometers. Aneroid barometers do not contain mercury or any other liquid, but they have a sealed and air-tight metallic chamber. The chamber expands or contracts in response to pressure changes and a pointer on a dial is used to indicate pressure readings. Modern barometers are digital and are able to measure atmospheric pressure accurately and quickly. These electronic instruments display current atmospheric pressure readings across a display screen.