A climatology of strong large-scale ocean evaporation events. Part I : Identification, global distribution, and associated climate conditions

This paper presents an object-based, global climatology (1979-2014) of strong large-scale ocean evaporation (SLOE) and its associated climatic properties. SLOE is diagnosed using an ''atmospheric moisture uptake efficiency'' criterion related to the ratio of surface evaporation a...

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Bibliographic Details
Published in:Journal of Climate
Main Authors: Aemisegger, Franziska, Papritz, Lukas
Format: Article in Journal/Newspaper
Language:English
Published: American Meteorological Society 2018
Subjects:
Climate Research
Air-sea interaction
Evaporation
Extratropical cyclones
Hydrologic cycle
Water vapor
Indian
North Atlantic
North Atlantic oscillation
Sea ice
Online Access:https://lup.lub.lu.se/record/e6857559-bb61-428d-a2d5-33b9e7041a0c
https://doi.org/10.1175/JCLI-D-17-0591.1
Description
Summary:This paper presents an object-based, global climatology (1979-2014) of strong large-scale ocean evaporation (SLOE) and its associated climatic properties. SLOE is diagnosed using an ''atmospheric moisture uptake efficiency'' criterion related to the ratio of surface evaporation and integrated water vapor content in the near-surface atmosphere. The chosen Eulerian identification procedure focuses on events that strongly contribute to the available near-surface atmospheric humidity. SLOE is particularly frequent along the warm ocean western boundary currents, downstream of large continental areas, and at the sea ice edge in polar regions with frequent cold-air outbreaks. Furthermore, wind-driven SLOE occurs in regions with topographically enforced winds. On a global annual average, SLOE occurs only 6% of the time but explains 22% of total ocean evaporation. An analysis of the past history and fate of air parcels involved in cold season SLOE in the North Atlantic and south Indian Oceans shows that cold-air advection is the main mechanism that induces these events. Extratropical cyclones thereby play an important role in setting the necessary equatorward synoptic flow. Consequently, the interannual variability of SLOE associated with the North Atlantic Oscillation and the southern annular mode reveals a very high sensitivity of SLOE with respect to the location of the storm tracks. This study highlights the strong link between transient synoptic events and the spatiotemporal variability in ocean evaporation patterns, which cannot be deduced from thermodynamic steadystate and climate mean state considerations alone.

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