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

It is sunny when the air pressure is high, and rainy when the air pressure is low. This is what the weatherman often says.

On the same horizontal plane, if the air pressure distribution is uneven, the air will flow from the high pressure area to the low pressure area. Therefore, if the air pressure in a certain area is high, the air in that area will flow out horizontally. The air above the high pressure area will drop. Because the air pressure increases with the decrease of altitude, when the air at high altitude falls, the pressure is increased, the volume is decreased, the temperature is increased, and the condensate in the air evaporates and dissipates. Therefore, the high-pressure central area is not conducive to the formation of clouds and rain, and it is often sunny. If the air pressure in a certain area is low, the air in the surrounding area will flow into the area horizontally, which will cause the air in the area to rise. The rising air will expand due to the pressure reduction, and the temperature will drop, and the water vapor in the air will condense, so the low-pressure central area is often rainy.

The atmospheric pressure is not completely equal everywhere. Atmospheric flow, eddy current, etc. Will cause different air pressures in different areas. Generally, when the air pressure in the vortex center is low, rainy weather will appear soon. The high voltage control area will be cleared.