Abstract
PUBLICTION No.5, 1919, of tne Royal Observatory ot Batavia, entitled “Atmospheric Varia1tions of Short and Long Duration in the Malay Archipelago and Neighbouring Regions, and the Possibility to Forecast Ihem,” by Dr. c. braaic, embodies the results ot a long investigation into the sequence ot rainfall in the equatorial regions east of the Indian Ocean. Three kinds of variation are studied: (1) with periods of one or more years up to and including the sun-spot period, (2) secular variations, and (3) with periods less than a month, comparable with Abbot's short-period solar fluctuations. The variations, the period of which is intermediate between (1) and (3) above, are treated as disturbances of (1). Dr. Braak lays much stress on a three-year period, of the persistence of which he gives plausible, though not quite convincing, examples. He classifies three groups of years, of high barometer, low barometer, and transition (from high to low), but naturally finds a proportion of years not strictly true to any of these types. It is scarcely surprising that he finds in general a correlation between barometric pressure and rainfall. For the east monsoon he finds strong positive correlation between high pressure and drought, and weaker between low pressure and excess of rain. For the west monsoon he finds, with some local exceptions, excess of rain with high barometer, and deficit with low barometer. His problem is thus reduced to the intensity of the correlation and the chances of a correct forecast of the barometer variation. His next step takes into account temperature changes which may be expected to modify pressure conditions, but his result is disappointing. He obtains rules, but their application is so far a failure that they appear to break down most thoroughly in years of drought—that is, when, if correct, they would be most valuable.
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B, W. Long-range Forecasting in Java. Nature 105, 729–730 (1920). https://doi.org/10.1038/105729a0
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DOI: https://doi.org/10.1038/105729a0