High‐Frequency Isotope Compositions Reveal Different Cloud‐Top and Vertical Stratiform Rainfall Structures in the Inland Tropics of Brazil

Abstract

AbstractUnderstanding the key drivers controlling rainfall stable isotope variations in inland tropical regions remains a global challenge. We present novel high‐frequency isotope data (5–30 min intervals) to disentangle the evolution of six stratiform rainfall events (N = 112) during the passage of convective systems in inland Brazil (September 2019–June 2020). These systems produced stratiform rainfall of variable cloud features. Depleted stratiform events (δ18Oinitial ≤ −4.2‰ and δ18Omean ≤ −6.1‰) were characterized by cooler cloud‐top temperatures (≤−38°C), larger areas (≥48 km2), higher liquid‐ice ratios (≥3.1), and higher melting layer heights (≥3.8 km), compared to enriched stratiform events (δ18Oinitial ≥ −3.8‰ and δ18Omean ≥ −5.1‰). Cloud vertical structure variability was reflected in a wide range of δ18O temporal patterns and abrupt shifts in d‐excess. Our findings provide a new perspective to the ongoing debate about isotopic variability and the partitioning of rainfall types across the tropics.