Earth's atmosphere is divided in several layers, one of them will concern us particularly for the weather things: the Troposphere. It ranges in altitude up to fifteen kilometers at the equator to its maximum, and it is the main action's playground for weather. The troposphere's boundary is called tropopause.
1)The wind
Air is a very poor conductor of heat, Uneven atmosphere's warming on earth will create warm air and cold air currents. These currents will move and act on the weather differently. Warm currents, less dense so lighter, will tend to “rise” Unlike cold currents, more dense so heavier. limits between those currents will create things that we call fronts. Wind is the result of an exchange between these air masses.
2)The main systems
In our middle temperate latitudes the weather is organized around two main systems: high pressure systems(anticyclone) and low pressure systems. Anticyclones correspond to dense air masses, dry and cold, relatively stationary, and LPS warm air masses and rather humid, relatively moving. Whatever hemisphere, air always goes from high pressures(so high pressure systems)to low pressures(Low pressure systems).
3)Basic laws
.Buys-ballot rule: In the northern hemisphere when we are in face with the wind, we have low pressures on his right. In the southern hemisphere it's the opposite. To summarize in the northern hemisphere the wind rotates anticlockwise around LPS, and clockwise around HPS(it is the opposite for the southern hemisphere).
.Coriolis Force: It's due to the earth rotational motions. It deviates to the right movements of large masses(winds and ocean currents)in the northern hemisphere and on the left in the southern hemisphere.