Meteorologia do Nordeste brasileiro

Resumo

The present article continues the research studies on the "dry seasons”, which were initiated with the publication of "Equatorial Climatology " In this study, we first analyze the overall picture of the annual migration of the doldrums precipitations, which we deduce occur from January in the northeast region. In order to explain the notable anomalies which constitute the years of dryness or of inundation, it seems better in view of the problem's complexity, to begin by studying the "dally variations" of the weather, the causes of which are described in detail.

            In the first chapter by means of 300 synoptic maps, careful examination is made of disturbances in two recent years, 1932 and 1935, of scarce and excessive rainfall respectively. It is shown that clear days coincide with small frontal advances in southern Brazil, the alísio of the southeast then advancing upon the northeast where a simultaneous increase of pressure and temperature takes place.

            On the other hand. the humid epochs ate determined by the front with a southeast-northeast trajectory. These push the center of action toward the ocean and permit the continental thunderstorms to reach Ceará Likewise, the formation of great cyclones in Argentina attracting all circulation towards the south, pulls the showers of the doldrums as far south as the São Francisco river.

            In the second chapter, after studying the normal upper circulation, various modifications are described. The extreme importance of the raised anticyclone of summer is demonstrated. The latter, besides forming a characteristic discontinuity, draws the lower tropopause of the central depression to the east. In the third part, the influence o f this last fact is emphasized.

            In the third and last part, besides a description of air masses, based on 1944 soundings, the mechanism of weather changes meets its logical explanation in an original manner. The mechanism is Judged to be the modifications in the height of the tropopause Thus is delineated the cause of equatorial phenomena always moving from "above to below"

            It is not the author's intent or indeed his specialty to consider in this article the problem of practical prediction of these Northeastern dry seasons, although such prediction is perfectly possible in the present state of science