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Abstract Water isotopes are tracers of convective processes and are often used as proxies for past precipitation. These applications require a better understanding of the impact of convective processes on the isotopic composition of water vapor and precipitation. One way to advance this understanding is to analyze the isotopic mesoscale variations during organized convective systems such as tropical cyclones or squall lines. The goal of this study is to understand these isotopic mesoscale variations with particular attention to isotopic signals in near‐surface vapor and precipitation that may be present in observations and in paleoclimate proxies. With this aim, we run cloud resolving model simulations in radiative‐convective equilibrium in which rotation or wind shear is added, allowing us to simulate tropical cyclones or squall lines. The simulations capture the robust aspects of mesoscale isotopic variations in observed tropical cyclones and squall lines. We interpret these variations using a simple water budget model for the sub‐cloud layer of different parts of the domain. We find that rain evaporation and rain‐vapor diffusive exchanges are the main drivers of isotopic depletion within tropical cyclones and squall lines. Horizontal advection spreads isotopic anomalies, thus reshaping the mesoscale isotopic pattern. This study contributes to our understanding of mesoscale isotopic variability and provides physical arguments supporting the interpretation of paleoclimate isotopic archives in tropical regions in terms of past cyclonic activity.
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Comparing Convective Self‐Aggregation in Idealized Models to Observed Moist Static Energy Variability Near the Equator
Abstract Idealized convection‐permitting simulations of radiative‐convective equilibrium have become a popular tool for understanding the physical processes leading to horizontal variability of tropical water vapor and rainfall. However, the applicability of idealized simulations to nature is still unclear given that important processes are typically neglected, such as lateral water vapor advection by extratropical intrusions, or interactive ocean coupling. Here, we exploit spectral analysis to compactly summarize the multiscale processes supporting convective aggregation. By applying this framework to high‐resolution reanalysis data and satellite observations in addition to idealized simulations, we compare convective‐aggregation processes across horizontal scales and data sets. The results affirm the validity of the radiative‐convective equilibrium simulations as an analogy to the real world. Column moist static energy tendencies share similar signs and scale selectivity in convection‐permitting models and observations: Radiation increases variance at wavelengths above 1,000 km, while advection damps variance across wavelengths, and surface fluxes mostly reduce variance between 1,000 and 10,000 km.
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- PAR ID:
- 10453135
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 46
- Issue:
- 17-18
- ISSN:
- 0094-8276
- Page Range / eLocation ID:
- p. 10589-10598
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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