High-Frequency Isotopic Analysis Unveils the Complexity of Convective Rainfall Dynamics in the Central Amazon

The Amazon region is recognized as one of the world's most significant active convective areas, generating precipitation systems that regulate the climate and weather across the region. Climate projections indicate increased convection over South America, expected to intensify extreme events and amplify their impacts on society. Stable water isotopes are a valuable tool for investigating the formation and evolution of extreme rainfall events in tropical regions. This study presents high-frequency (5-30 minutes) isotope data for rainfall (n=115) and vapor (Picarro Inc., USA L2140i analyzer) from 19 convective events at the ATTO tower site (25/Jan-08/Feb 2024), coupled with various meteorological data (Rain Micro Radar, ATTO tower, Reanalysis, GOES-16). Rainfall and vapor exhibited distinct isotopic signatures with similar temporal trends, with vapor being more depleted in 𝛿¹⁸O (-13.78 to -8.92‰) than rainfall (-6.28 to +1.03‰).  Rainfall events were short-lived (< 1 hour) and associated with lower cloud top temperature (-33ºC to +9°C). The averaged 𝛿¹⁸O variability within (intra-) and between events (intra: -6.28 to -4.03‰, between: -5.13‰ and +1.03‰), suggests a complex interplay of factors influencing precipitation formation. These factors likely include moisture transport, limited vertical development, and the incorporation of forest evapotranspiration. This study provides valuable insights into the intricate relationship between the Amazon rainforest and rainfall formation. The generated knowledge and data can contribute to improving atmospheric models and understanding the potential impacts of climate change on the Amazon's hydroclimatic system.