What controls the water vapor isotopic composition near the surface of tropical oceans? Results from an analytical model constrained by large‐eddy simulations

Risi C, MULLER CJ, Blossey P. 2020. What controls the water vapor isotopic composition near the surface of tropical oceans? Results from an analytical model constrained by large‐eddy simulations. Journal of Advances in Modeling Earth Systems. 12(8), e2020MS002106.


Journal Article | Published | English
Author
Risi, Camille; MULLER, Caroline JIST Austria; Blossey, Peter
Abstract
The goal of this study is to understand the mechanisms controlling the isotopic composition of the water vapor near the surface of tropical oceans, at the scale of about a hundred kilometers and a month. In the tropics, it has long been observed that the isotopic compositions of rain and vapor near the surface are more depleted when the precipitation rate is high. This is called the “amount effect.” Previous studies, based on observations or models with parameterized convection, have highlighted the roles of deep convective and mesoscale downdrafts and rain evaporation. But the relative importance of these processes has never been quantified. We hypothesize that it can be quantified using an analytical model constrained by large‐eddy simulations. Results from large‐eddy simulations confirm that the classical amount effect can be simulated only if precipitation rate changes result from changes in the large‐scale circulation. We find that the main process depleting the water vapor compared to the equilibrium with the ocean is the fact that updrafts stem from areas where the water vapor is more enriched. The main process responsible for the amount effect is the fact that when the large‐scale ascent increases, isotopic vertical gradients are steeper, so that updrafts and downdrafts deplete the subcloud layer more efficiently.
Publishing Year
Date Published
2020-08-01
Journal Title
Journal of Advances in Modeling Earth Systems
Volume
12
Issue
8
Article Number
e2020MS002106
IST-REx-ID

Cite this

Risi C, MULLER CJ, Blossey P. What controls the water vapor isotopic composition near the surface of tropical oceans? Results from an analytical model constrained by large‐eddy simulations. Journal of Advances in Modeling Earth Systems. 2020;12(8). doi:10.1029/2020ms002106
Risi, C., MULLER, C. J., & Blossey, P. (2020). What controls the water vapor isotopic composition near the surface of tropical oceans? Results from an analytical model constrained by large‐eddy simulations. Journal of Advances in Modeling Earth Systems. American Geophysical Union. https://doi.org/10.1029/2020ms002106
Risi, Camille, Caroline J MULLER, and Peter Blossey. “What Controls the Water Vapor Isotopic Composition near the Surface of Tropical Oceans? Results from an Analytical Model Constrained by Large‐eddy Simulations.” Journal of Advances in Modeling Earth Systems. American Geophysical Union, 2020. https://doi.org/10.1029/2020ms002106.
C. Risi, C. J. MULLER, and P. Blossey, “What controls the water vapor isotopic composition near the surface of tropical oceans? Results from an analytical model constrained by large‐eddy simulations,” Journal of Advances in Modeling Earth Systems, vol. 12, no. 8. American Geophysical Union, 2020.
Risi C, MULLER CJ, Blossey P. 2020. What controls the water vapor isotopic composition near the surface of tropical oceans? Results from an analytical model constrained by large‐eddy simulations. Journal of Advances in Modeling Earth Systems. 12(8), e2020MS002106.
Risi, Camille, et al. “What Controls the Water Vapor Isotopic Composition near the Surface of Tropical Oceans? Results from an Analytical Model Constrained by Large‐eddy Simulations.” Journal of Advances in Modeling Earth Systems, vol. 12, no. 8, e2020MS002106, American Geophysical Union, 2020, doi:10.1029/2020ms002106.
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