Bilan hydrique global : " En hémisphère Nord, pleut-il davantage durant le second semestre ? Et inversement en hémisphère Sud ? "

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In north hemisphere, the amount of precipitable water in atmosphere is greater at summer solstice than at winter solstice. This explains a part of seasonnal variation in precipitation. During the first calendar half year, rainfall amount is reduced because the atmospheric humidity increases. On the contrary, during the second calendar halfyear, rainfall amount is increased by atmospheric drying. This schematic sight, inversed in south hemisphere, is roughly supported by the 1931-1960 Normal monthly precipitation study, with however exceptions and shades. This ascertainment questions the reader about water balance and induces new research prospects.