Rainfall variability modes in the State of São Paulo, Brazil: local, regional and remote connections

Abstract

Precipitation can impact almost all human activities, which makes it's distribution in time and space strategic scientific information. The evaluation of the precipitation becomes even more important in places of great complexity, as the State of São Paulo, because besides the great variability of this element due to it's transitional geographical position (the area is crossed by the Tropic of Capricorn, under influences of distinct atmospheric systems), the great socio-economic dynamism of this federal unit causes the water demand to be steadily high, so rainfall variability can carry quite hefty consequences. Despite the many contributions that have been adding to the understanding rainfall variability in the State of São Paulo, a permanent high water demand and changes in rainfall patterns in recent years highlight the need for new areas of research that incorporate new knowledge to understand the variability of atmospheric precipitation. In this context, this research seeks to understand the patterns and trends of this space-time variability in the State of São Paulo, evaluating it with parametric statistics along the use of GIS techniques to treat data of rainfall stations with long-term records. The analysis are taken at various scales, in order to understand where and when the variability is greater, if changes in rain distribution patterns are happening, and which remote mechanisms could interfere with rainfall in the state territory. Partial study results shows that in recent years there has been significant change in rainfall distribution patterns in the State of São Paulo. The changes observed in both parameters of the gamma distribution and in the number of extreme events, are solid evidence of these changes - a phenomenon that could not be seen only with the study of total rainfall. Comparing the rainfall patterns in São Paulo in two periods - 1993-2012 and 1973-1992 - it's noted an increase in irregularity of the rainfall distribution and hence the uncertainty related to rainfall patterns, with important implications for human activities such as management of water resources and agricultural planning. The fact that these changes are happening simultaneously over the whole state, ie not be spatially specific, it emphasizes that such changes could be linked to remote conditions in addition to those local and regional, especially in a context of global climate change. This fact demands the continuity of the analysis of the initial proposal, but also the incorporation of new reviews: at the spatial level, possible influences of teleconnections and at the temporal level, analysis of daily data in order to identify other patterns. The way these changes could impact the economy and the physical processes in the State of São Paulo should also be considered, which implies further research in order to answer new questions that arose with the advancement of research. Following recommendations, I intend, together with my advisor, to expand the study, continuing the initially planned teleconnection analysis, associating with approaches that assess the concentration of daily rainfall with special emphasis on the coastal sector, site of greatest interest in the thematic project 2012/51876-0. (AU)