Why is the air pressure lower on sunny days than on rainy days?

Because there is more water in the air in rainy days, and the molecular weight of water is smaller than the average molecular weight of air 29 18, the air density in cloudy days is relatively small, while the atmospheric pressure is related to the air density, which is high and low. Therefore, the reason for the low atmospheric pressure in rainy days is that both the atmosphere and the liquid are flowing, and they are both affected by gravity due to the gravity of the earth. Therefore, the atmosphere around the earth will also exert pressure on the objects immersed in it, which is called atmospheric pressure. The famous experiment in the hemisphere of Fort Madre in history proved the existence of atmospheric pressure. The value of atmospheric pressure can be measured by Torricelli experiment. The value of 1 standard atmospheric pressure is equal to the pressure generated by a mercury column 760mm high. That is, the change of atmospheric pressure (1.0 1× 10 5 Pascal. 3) The higher the ground, the thinner the air and the smaller the air density. Within 2000 meters above sea level, it can be approximately considered that the atmospheric pressure decreases by 12 meters for every increase in altitude. The air pressure in winter is higher than that in summer. Atmospheric pressure is related to the density of air, and the density of water vapor is less than that of air (mainly depending on nitrogen and oxygen). There is more water vapor in the air on cloudy days, and the air pressure becomes lower! Although air is a mixture containing many gases, it can be simply divided into two parts: water vapor and other dry air without water vapor. When the atmospheric change is regarded as a quasi-static process and there is no heat exchange, that is, the atmospheric pressure is formed by adding the pressures generated by these two parts, which is the sum of the weight of water vapor in the above-mentioned gas column and the weight of dry air.