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Effects of a Cold Ocean Eddy on Local Atmospheric Boundary Layer Near the Kuroshio Extension: In Situ Observations and Model Experiments
Author(s) -
Jiang Yuxi,
Zhang Suping,
Xie Shangping,
Chen Yang,
Liu Haikun
Publication year - 2019
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2018jd029382
Subject(s) - geology , sea surface temperature , planetary boundary layer , climatology , mixed layer , atmospheric sciences , convection , eddy diffusion , environmental science , turbulence , meteorology , geography
Shipboard observations captured clear modulations of the marine atmospheric boundary layer (MABL) over a 300‐km‐diameter cold eddy in the Kuroshio Extension in April 2014. Regional atmospheric model experiments, with 30‐km and 10‐km horizontal resolutions for outer and inner domains, respectively, are conducted to aid the interpretations of the in situ observations. Enhanced turbulent heat fluxes promoted a well‐mixed MABL up to 1900‐m deep and a stratocumulus layer over the warm water west of the eddy. Over the cold sea surface of the eddy, the MABL was free of cloud and shrank to 1,200‐m deep. In the transition zone from the warm water in the west to the cold eddy, the MABL deepened and convective cumulus developed under a temperature inversion at 2,800 m. Model results indicate that, via the vertical mixing and pressure adjustment mechanisms, low sea surface temperatures of the cold eddy drives anomalous easterly winds in the transition zone, causing surface convergence to deepen the MABL and clouds. The model further shows that the atmospheric asymmetric responses in surface divergence and secondary circulation are due to the combined effects of the vertical mixing and pressure adjustment.