Solar radiation and the rotation of the earth keep the air masses in the atmosphere in motion. This causes constantly alternating high-and low-pressure areas to be distributed across the planet. A low-pressure area- also known as a cyclone, and not to be confused with the tropical system of the same name- develops when the surrounding air converges towards an area of low presssure at the surface and then rises in to the atmosphere. The formation of low- pressure areas – known as cyclogenesis-occurs when air moves away from an area of high pressure and the air above subsides.
