What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations

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 va...

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Autores principales:	Camille Risi, Caroline Muller, Peter Blossey
Formato:	article
Lenguaje:	EN
Publicado:	American Geophysical Union (AGU) 2020
Materias:	water isotopes convection large‐eddy simulation Physical geography GB3-5030 Oceanography GC1-1581
Acceso en línea:	https://doaj.org/article/786bcb28cdeb49a1a63a1b0ac29a3fd8
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spelling	oai:doaj.org-article:786bcb28cdeb49a1a63a1b0ac29a3fd82021-11-15T14:20:27ZWhat Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations1942-246610.1029/2020MS002106https://doaj.org/article/786bcb28cdeb49a1a63a1b0ac29a3fd82020-08-01T00:00:00Zhttps://doi.org/10.1029/2020MS002106https://doaj.org/toc/1942-2466Abstract 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.Camille RisiCaroline MullerPeter BlosseyAmerican Geophysical Union (AGU)articlewater isotopesconvectionlarge‐eddy simulationPhysical geographyGB3-5030OceanographyGC1-1581ENJournal of Advances in Modeling Earth Systems, Vol 12, Iss 8, Pp n/a-n/a (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	water isotopes convection large‐eddy simulation Physical geography GB3-5030 Oceanography GC1-1581
spellingShingle	water isotopes convection large‐eddy simulation Physical geography GB3-5030 Oceanography GC1-1581 Camille Risi Caroline Muller 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
description	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.
format	article
author	Camille Risi Caroline Muller Peter Blossey
author_facet	Camille Risi Caroline Muller Peter Blossey
author_sort	Camille Risi
title	What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations
title_short	What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations
title_full	What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations
title_fullStr	What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations
title_full_unstemmed	What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations
title_sort	what controls the water vapor isotopic composition near the surface of tropical oceans? results from an analytical model constrained by large‐eddy simulations
publisher	American Geophysical Union (AGU)
publishDate	2020
url	https://doaj.org/article/786bcb28cdeb49a1a63a1b0ac29a3fd8
work_keys_str_mv	AT camillerisi whatcontrolsthewatervaporisotopiccompositionnearthesurfaceoftropicaloceansresultsfromananalyticalmodelconstrainedbylargeeddysimulations AT carolinemuller whatcontrolsthewatervaporisotopiccompositionnearthesurfaceoftropicaloceansresultsfromananalyticalmodelconstrainedbylargeeddysimulations AT peterblossey whatcontrolsthewatervaporisotopiccompositionnearthesurfaceoftropicaloceansresultsfromananalyticalmodelconstrainedbylargeeddysimulations
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What Controls the Water Vapor Isotopic Composition Near the Surface of Tropical Oceans? Results From an Analytical Model Constrained by Large‐Eddy Simulations

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