Note on the temperature ramp structure in the marine surface layer

Abstract The influence of swell on turbulence and scalar profiles in a marine surface layer and underlying physics is examined in this study through diagnosis of large-eddy simulations (LES) that explicitly resolve the surface layer and underlying swell. In general, under stable conditions, the mean wind and scalar profiles can be significantly modified by swell. The influence of swell on wind shear, turbulence structure, scalar profiles, and evaporation duct (ED) characteristics becomes less pronounced in a more convective boundary layer, where the buoyancy production of turbulence is significant. Dynamically, swell has little direct impact on scalar profiles. Instead it modifies the vertical wind shear by exerting pressure drag on the wave boundary layer. The resulting redistribution of vertical wind shear leads to changes in turbulence production and therefore turbulence mixing of scalars. Over swell, the eddy diffusivities from LES systematically deviate from the Monin–Obukhov similarity theory (MOST) prediction, implying that MOST becomes invalid over a swell-dominated sea. The deviations from MOST are more pronounced in a neutral or stable boundary layer under relatively low winds and less so in a convective boundary layer.

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A numerical study of the marine surface layer in a sea breeze regime

Ocean Management ◽

10.1016/0302-184x(81)90032-9 ◽

1981 ◽

Vol 6 (2-3) ◽

pp. 111-116 ◽

Cited By ~ 2

Author(s):

G.A. Dalu ◽

R. Purini

Keyword(s):

Surface Layer ◽

Numerical Study ◽

Sea Breeze ◽

Marine Surface Layer ◽

Marine Surface

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Centimeter-scale-resolution airborne temperature measurements in clouds and in marine surface layer during EUREC4A

10.5194/egusphere-egu21-14645 ◽

2021 ◽

Author(s):

Stanisław Król ◽

Szymon Malinowski ◽

Wojciech Kumala ◽

Jakub Nowak ◽

Robert Grosz ◽

...

Keyword(s):

Surface Layer ◽

Sampling Rate ◽

Temperature Measurements ◽

Small Scale ◽

Temperature Structure ◽

Scale Temperature ◽

Marine Surface Layer ◽

Marine Surface ◽

Temperature Records

Characterization of small-scale temperature structure of convective clouds and their environment is crucial to understand turbulent entrainment, mixing and its effect on cloud dynamics and microphysics. A newly constructed ultra-fast thermometer UFT2, developed from the former UFT-M, allowing for temperature measurements in clouds with the resolution better than few centimeters, was deployed on the British Antarctic Survey Twin-Otter research aircraft in the course of the EUREC4A research campaign. The goal was to perform first ever fine-scale temperature characterization of subtropical marine warm cumulus clouds.The prototype instrument worked relatively well and allow to collect data from 7 of 17 research flights, including hundreds of cloud penetrations and segments of flights in the marine surface layer. Data, collected with 20 kHz sampling rate, after filtering and averaging allowed to achieve physical resolution of ~3cm at ~60m/s true air speed of the aircraft.Performance of the UFT-2 sensor and its calibration will be discussed. The discussion will be illustrated with examples of multi-scale temperature records collected in cloud interiors, cloud edges, cloud shells at various altitudes as well as in the marine surface layer ~30 m above the sea level.

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