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A climatology of strong large-scale ocean evaporation events. Part II : Relevance for the deuterium excess signature of the evaporation flux

Aemisegger, Franziska and Sjolte, Jesper LU orcid (2018) In Journal of Climate 31(18). p.7313-7336
Abstract

This paper discusses the relevance of transient events of strong large-scale ocean evaporation (SLOE) for the deuteriumexcess of marine boundary layer vapor d using a theoretical framework that invokes the closure assumption. We argue that during SLOE events, d is essentially determined by the evaporation flux signature. Distinct high d during SLOE with global-mean values in the range of 12‰-23‰ depending on the nonequilibrium fractionation factor αk result from the large air-sea humidity gradients reflected in low relative humidity with respect to sea surface temperature (hs 5 53% ± 9%) that characterize these events. Extratropical cyclones are highlighted as an important driver for the variability of d. On the... (More)

This paper discusses the relevance of transient events of strong large-scale ocean evaporation (SLOE) for the deuteriumexcess of marine boundary layer vapor d using a theoretical framework that invokes the closure assumption. We argue that during SLOE events, d is essentially determined by the evaporation flux signature. Distinct high d during SLOE with global-mean values in the range of 12‰-23‰ depending on the nonequilibrium fractionation factor αk result from the large air-sea humidity gradients reflected in low relative humidity with respect to sea surface temperature (hs 5 53% ± 9%) that characterize these events. Extratropical cyclones are highlighted as an important driver for the variability of d. On the one hand, they are themselves associated with high hs and low d, especially in areas of cloud formation and precipitation in the warm sector. On the other hand, cyclones are the main driver inducing SLOE events with high d in regions of cold-air advection upstream of their path. The sensitivity of d to its direct climate controls (hs and SST) is analyzed during SLOE for different αk formulations and found to be coherent with d-hs and d-SST slopes determined from available observations. The d-hs relationship exhibits a robust negative correlation as opposed to the d-SST relationship, which shows regional and time-scale-dependent variations in strength and sign that are induced by indirect hs-SST cross-correlation effects. The dynamical features involved in SLOE generation appear to exert a key control on the moisture source properties relevant for d in the extratropics.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Air-sea interaction, Evaporation, Extratropical cyclones, Water vapor
in
Journal of Climate
volume
31
issue
18
pages
24 pages
publisher
American Meteorological Society
external identifiers
  • scopus:85052927027
ISSN
0894-8755
DOI
10.1175/JCLI-D-17-0592.1
language
English
LU publication?
yes
id
b1e81831-41a5-4dfe-b472-56e3f1f0ec3d
date added to LUP
2018-10-12 09:47:52
date last changed
2022-04-25 18:04:22
@article{b1e81831-41a5-4dfe-b472-56e3f1f0ec3d,
  abstract     = {{<p>This paper discusses the relevance of transient events of strong large-scale ocean evaporation (SLOE) for the deuteriumexcess of marine boundary layer vapor d using a theoretical framework that invokes the closure assumption. We argue that during SLOE events, d is essentially determined by the evaporation flux signature. Distinct high d during SLOE with global-mean values in the range of 12‰-23‰ depending on the nonequilibrium fractionation factor α<sub>k</sub> result from the large air-sea humidity gradients reflected in low relative humidity with respect to sea surface temperature (h<sub>s</sub> 5 53% ± 9%) that characterize these events. Extratropical cyclones are highlighted as an important driver for the variability of d. On the one hand, they are themselves associated with high h<sub>s</sub> and low d, especially in areas of cloud formation and precipitation in the warm sector. On the other hand, cyclones are the main driver inducing SLOE events with high d in regions of cold-air advection upstream of their path. The sensitivity of d to its direct climate controls (h<sub>s</sub> and SST) is analyzed during SLOE for different α<sub>k</sub> formulations and found to be coherent with d-h<sub>s</sub> and d-SST slopes determined from available observations. The d-h<sub>s</sub> relationship exhibits a robust negative correlation as opposed to the d-SST relationship, which shows regional and time-scale-dependent variations in strength and sign that are induced by indirect h<sub>s</sub>-SST cross-correlation effects. The dynamical features involved in SLOE generation appear to exert a key control on the moisture source properties relevant for d in the extratropics.</p>}},
  author       = {{Aemisegger, Franziska and Sjolte, Jesper}},
  issn         = {{0894-8755}},
  keywords     = {{Air-sea interaction; Evaporation; Extratropical cyclones; Water vapor}},
  language     = {{eng}},
  number       = {{18}},
  pages        = {{7313--7336}},
  publisher    = {{American Meteorological Society}},
  series       = {{Journal of Climate}},
  title        = {{A climatology of strong large-scale ocean evaporation events. Part II : Relevance for the deuterium excess signature of the evaporation flux}},
  url          = {{http://dx.doi.org/10.1175/JCLI-D-17-0592.1}},
  doi          = {{10.1175/JCLI-D-17-0592.1}},
  volume       = {{31}},
  year         = {{2018}},
}