ABSTRACT
Having accounted for the key processes in the atmosphere at all scales and touched upon how they blend together in the more familiar setting of towns, it remains to survey the global scene likewise. Several factors combine to explain the weather of the tropical world. Foremost is the weak Coriolis force up to 10° of latitude either side of the Equator. Beyond latitude 40°, temperature increasingly takes over as the dominant feature of weather patterns. With shorter zonal circuits around the Earth, the Coriolis force becomes stronger too. The zonal tracks of mid-latitude depressions across Europe are often blocked in winter when the snows arrive on the mountains and the interior cools to set up stable cold-core highs. There is growing evidence from actual records and historical information that similar cycling of the circum-polar vortex occurs over longer periods of time causing rhythmic climatic changes.
