The relationship between air pressure and physics in grade three!

Clouds on cloudy days reduce the outward divergence of troposphere atmosphere, and the inverse radiation is weakened, so there are more water vapor (gas) in cloudy days than in sunny days, but it is also composed of water molecules, because the molecular weight of water is lower than the average molecular weight of air, and because the number of gas molecules in the same unit volume is equal or the difference is small at the same temperature, the atmospheric pressure of air is low due to high humidity. There is more water vapor in the air on cloudy days than on sunny days, and the molecular weight of water is lower than the average molecular weight of air, which reduces the density of the atmosphere, so the air pressure on cloudy days is lower than on sunny days.