How does air pressure affect weather?

Regions with high pressure on the ground tend to have sunny days, while areas with low pressure on the ground tend to have rainy days. The high pressure and low pressure mentioned here are relative and do not refer to the absolute value of atmospheric pressure. If the air pressure in a certain area is higher than the air pressure in the surrounding areas, it is called a high pressure area; if the air pressure in a certain area is lower than the air pressure in the surrounding areas, it is called a low pressure area.

On the same horizontal plane, if the air pressure distribution is uneven, air will flow from high pressure areas to low pressure areas. Therefore, the air pressure in a certain area is high, and the air in that area flows horizontally to surrounding areas.

The air above the high pressure area will drop. Since atmospheric pressure increases with decreasing height, when the air at high altitudes descends, the pressure it experiences increases, its volume decreases, its temperature increases, and the condensation in the air evaporates and dissipates.

Influencing factors:

The magnitude of air pressure is related to altitude, atmospheric temperature, atmospheric density, etc. It generally decreases exponentially with increasing altitude, and air pressure has diurnal and annual changes.

The air pressure is higher in winter than in summer. During the day, the air pressure has a maximum value and a minimum value, which appear at 9 to 10 o'clock and 15 to 16 o'clock respectively. There is also a second highest value and a second low value, which appears at 21 to 22 o'clock and 3 to 4 o'clock respectively. . The daily variation in air pressure is small, generally 0.1 to 0.4 kPa, and decreases with increasing latitude.

The commonly used instruments for measuring air pressure in meteorological observations include mercury barometers, empty box barometers, and barometers. The pressure at the height of a vertical mercury column of 760 mm when the temperature is 0°C. The standard atmospheric pressure was first measured by Italian scientist Torricelli.