Rainfall isotopic composition variability in the central portion of the state of São Paulo based on intra-event analysis

Abstract

Stable isotopes of hydrogen (1H/2H) and oxygen (16O/17O/18O) are excellent tracers for the movement of the water molecule along the hydrological cycle. They are used as auxiliary tools for interpreting the origins of water, flows within river basins, climatic controls on precipitation, definition of groundwater origin and paleoclimatic reconstitution studies. In tropical areas the climatic factors that govern the variability on precipitation isotopic composition remain a controversial subject in the scientific community. Some authors suggest that the isotopic composition of precipitation is influenced by processes at the regional scale, others advocate the importance of local climate dynamics. The main results of previous studies carried out at the Rio Claro, based on monthly and daily monitoring schemes, showed that the variability on precipitation isotopic composition is mainly controlled by regional factors (atmospheric systems and continental moisture transport) coupled to vapor recirculation processes. Single events presenting very depleted or enriched composition could not be fully explained due to the lack of meteorological data and definition of local atmospheric processes, resulting in questions to be answered, mainly regarding the associations with different rainfall types showed in several precipitation isotopes studies. On this research with intra-event, these questions have been answered, with evaluated synoptic analysis (convective activity and moisture flux), rainfall type classification (convective and stratiform) by Micro Rain Radar and evaporative processes during isotopic variations in stratiform precipitation (lower rain rate > lower droplet > more evaporation). The final challenge of this research is to integrate the interpretations of intra-event collection and use them on larger scales. This integration is something that has not yet been done in tropical areas, due to the difficulty of maintaining long-term monitoring. The opportunity of the internship abroad, in a meteorology school and with the expertise of professor Dr. Ana María Durán-Quesada, especially in moisture transport and isotopic variability in tropical areas, helping the scholarship holder in his doctorate research and creating an enriched background in their professional, as a university professor in the future. (AU)