When on part of the planet heats up due to insolation (incoming solar heat), the air overhead also grows warmer, and the air pressure falls with increased heat and lowered density. Neighboring air which is not as warm, and is therefore denser and under higher pressure, will move into the area of lower pressure, as the warmer, lower-pressure air moves upward. This does not necessarily involve storms, as the temperature and pressure differences are not extreme, but the differences are great enough to get the air moving.
Two processes which illustrate this take place, one on a daily basis, the other annually. The daily cycle is the sea breeze/land breeze. During daytime, with the sunshine, the land heats up and becomes warmer than the adjacent ocean. The warm earth warms the air, which rises. Cooler, higher-pressure air over the water flows onto the land to take the place of the rising warm air: this is a sea breeze. At night, the land has lost much of its heat but the ocean remains warmer, creating an upward current of warm air there, with the cooler, denser air from the land flowing out toward the water: this is a land breeze. (Wind is named for its origin, not its destination.)
Seasonal monsoon.
The monsoon of India is the same thing, played out over the
course of the year. In summertime, the inland regions including the Himalaya
warm up, leading to a large mass of warmer, lower pressure air, which brings
the cooler (though still warm) wind from the ocean. It blows reasonably steadily
for several months, bringing with it the rain and storms common to the season.
In wintertime, the cold mountainous region cools the air, creating a huge high
pressure dome. This cooler, high-pressure air flows, for several months, back
out toward the warmer, lower-pressure air of ocean.
Tomorrow: global circulation cells.
Be well!
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