Winds and Fronts over Southeast Asia

T HE standard treatment of wind conditions near the equator postulates that trade winds blow toward the equator from the northeast and southeast in the Northern and Southern Hemispheres respectively. A seaman's term, the doldrums, is used to describe a belt of calms over the equator between the two trade-wind zones. In reality this conception derives almost entirely from theoretical consideration of the physical conditions on a revolving globe with a uniform surface. On the terrestrial globe certain difficulties obstruct the study of equatorial weather conditions. Only three parts of the equatorial zone are placed so that an adequate net of meteorological stations can be established; they are the Amazon Valley, Central Africa, and that complex of peninsulas and archipelagoes between Australia and Asia which may be described variously as Southeast Asia, Malaysia, or the East Indies. Not all these three equatorial regions, however, represent an approximation to theoretical equatorial conditions. The first two are really examples of the conditions over massive equatorial continents. Only the archipelagic area of Southeast Asia has its land masses broken up by sea surfaces of equal or greater area, and it therefore represents a closer approach to conditions that would operate over an equator on a globe with a uniform surface. Nevertheless, even the archipelago of Southeast Asia is flanked on the north by the largest of the continental land masses, Asia, and on the south by the smallest continent, Australia. Neither of these continents is equatorial, yet both exert strong influences on the equatorial wind system that develops between them. In Southeast Asia, the term that will be used in this paper to describe the whole archipelago as well as the adjoining peninsulas of Asia, the network of observing stations is open. Their observations have been correlated into nautical charts showing the mean transport of air in the Indian and West Pacific Oceans; and, although the data available-for the compilation of the charts are limited, they show the mean direction and degree of persistence of the wind in each part of a graticule of about 2? by latitude and by longitude. The charts thus compiled, drawn in the style of similar charts published by the British Admiralty for the North Atlantic on the basis of far more detailed material, are based on a regrettably short period of observation, generally less than ten years, and, in the open sea areas, on scanty and infrequent observations from ships. Despite these limitations, the ma

Ancient history · Climatology · Geography · Meteorology · Southeast asia · Geology · Geophysics and Gravity Measurements · History

• Ist in Ostasien der Sommermonsun der Hauptniederschlagsbringer

  Open Access•Hermann Lautensach•Erdkunde•1949

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