Recent rainfall trends on the margins of the subtropical deserts: A comparison of selected northern hemisphere regions |
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| Authors: | Roger Byrne Orman Granger John Monteverdi |
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| Institution: | 1. Department of Geography, University of California, Berkeley, California 94720 USA;2. Museum of Paleontology, University of California, Berkeley, California 94720 USA;3. Department of Earth Science, San Francisco State University, San Francisco, California 94132 USA |
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| Abstract: | An analysis of recent (1898–1972) seasonal rainfall data from California (winter) and Mexico (summer) provides no evidence of an inverse relationship such as has been reported by Winstanley for climatically analogous areas of Eurasia and Africa. However, California and Old World winter rain trends have been remarkably similar during this time period. Also, summer rain in northwestern Mexico (Mazatlan) correlates highly with winter rainfall in southern California (San Diego) when allowance is made for a 7-year lag. Winstanley suggested that the expansion and contraction of the circumpolar vortex is a primary control of rainfall trends on the margins of the subtropical deserts. The alternative proposed here is that, at least on this time scale, variations in the longitudinal position of troughs and ridges in the upper air westerlies are more important. |
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