National Geographic : 1984 Dec
Solar heal fuels the monsoon 0w08 8 cr MONSOON WINDS form one of the most massive weather systems in the world, part of the global heat transfer that keeps the planet habitable.Without the monsoons to balance temperatures, latitudes exposed to the sun's direct rays would shrivel with heat, and areas of centralAsia would succumb to deep, unimaginablecold. Although the most important monsoons oscillatebetween India,the FarEast, andAustralia,and their tropicaloceans, monsoon winds exist in Africa, Mexico, and perhaps even in the Arctic. In its basicform the monsoon is a A heat engine-anenormous cycle of airset in motion by temperature differences over land and sea. In summer land heats more rapidly because solarradiationdoes not penetrate below its surface. Water stays coolerbecause it mixes, but it stores heat in its upper layers for long periodsof time. Because the winds perform on a global scale, they are also directed by the tilt of the earthon its axis and by the Coriolisforce resultingfrom the earth'sspin. In a simplified model of a summer monsoon, below, airparcel X in diagram A is heated over the land while parcelY remains cooler over the sea. In diagram B,parcel X rises, expands, and sheds its moisture, allowing Y to flow inland to equalize air pressure.While crossing the sea, Y k ; ;" i;. :I"~' '-"