Abstract:

This study used the National Center for Atmospheric Research Large Eddy Simulation (NCAR-LES) model for the Ocean Surface Boundary Layer (OSBL). This model has been widely used to investigate boundary layer turbulence driven by various external surface forcing, as well as vertical mixing of particulate tracers such as gas bubbles, plastic debris and cohesive sediments. Recently, the model was also configured to study turbulence in the presence of a horizontal density gradient and to quantify horizontal dispersion and transport in the OSBL. The model can be requested from Dr. Peter Sullivan (pps@ucar.edu). There is no configuration or forcing files. All model setting is set in the code. In this study, the model is configured on an infinitely wide and stationary frontal zone. By systematically varying the wind/wave and frontal zone setup, as well as the domain size, this study aims at investigating the influence of a horizontal frontal zone on the wind- and wave-driven ocean surface boundary layers. The frontal zone is represented by a uniform lateral temperature gradient in the x-direction. The horizontal temperature gradient is sent to be 0.0153 K/km. A steady and uniform wind 10m above the ocean surface of 5 m/s is applied. The wind direction is systematically varied. The wind-front angle is the counterclockwise angle the wind makes with the upgradient direction. When the wind-front angle is 0-degree, the wind blows in the direction that the background temperature increases. When the wind-front angle is 90-degree, the wind blows in the down-front direction, with colder water on the left-hand side. Simulations are configured on two different domains: a large domain with horizontal extents of 1500m and a small one of 375m in both horizontal directions. For our chosen initial condition, if without wind stress, the large domain is sufficient for both unforced submesoscale eddies (SMEs) and OSBL turbulence to develop, while the small domain only allows OSBL turbulence to evolve. Contrasting solutions on the two domains under an otherwise identical setup allows the study of how SMEs affect the structure and turbulence of the OSBL in a frontal zone. This dataset supports the publication: Yuan, Jianguo and Jun-Hong Liang. (2021). Wind- and Wave-driven Ocean Surface Boundary Layer in a Frontal Zone: Roles of Submesoscale Eddies and Ekman-Stokes Transport. Journal of Physical Oceanography. doi:10.1175/jpo-d-20-0270.1.

Suggested Citation:

Yuan, Jianguo and Jun-Hong Liang. 2021. Dataset for: Wind- and Wave-Driven Ocean Surface Boundary Layer in a Frontal Zone: Roles of Submesoscale Eddies and Ekman–Stokes Transport. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N5B2FFP3

Publications:

Yuan, J., & Liang, J.-H. (2021). Wind- and Wave-driven Ocean Surface Boundary Layer in a Frontal Zone: Roles of Submesoscale Eddies and Ekman-Stokes Transport. Journal of Physical Oceanography. doi:10.1175/jpo-d-20-0270.1

Purpose:

The purpose is to study the wind- and wave-driven ocean surface boundary layer in the presence of a horizontal density gradient. The focus is on the effect of submesoscale eddies and advective heat flux on the stratification, mean current, and turbulence of the upper ocean. Those upper-ocean characteristics control the dispersion and transport of spilled oil.

Data Parameters and Units:

The dataset contains four NetCDF files, where two are snapshot files (“ins_ek.nc” and "“ins_wv.nc”) and the other two are the statistic files ("his_ek.nc" and "his_wv.nc"). The two snapshot files contain the instantaneous temperature and vertical velocity data at a depth of 10 m below the sea surface. The file “ins_ek.nc” contains the results in simulations without wave effects, while “ins_wv.nc” contains the results in simulations with wave effects. The snapshots were taken when the turbulent flow is fully spun up, 6 days after the simulation without wave effects started and 12 days after the simulations with wave effects started. Different snapshots in the files are for different wind-front angles. The parameters included are: T0 [Temperature Anomaly in the simulation where the wind-front angle is 0 degree (K)]; T45 [Temperature Anomaly in the simulation where the wind-front angle is 45 degree (K)]; T90 [Temperature Anomaly in the simulation where the wind-front angle is 90 degree (K)]; T135 [Temperature Anomaly in the simulation where the wind-front angle is 135 degree (K)]; T180 [Temperature Anomaly in the simulation where the wind-front angle is 180 degree (K)]; T225 [Temperature Anomaly in the simulation where the wind-front angle is 225 degree (K)]; T270 [Temperature Anomaly in the simulation where the wind-front angle is 270 degree (K)]; T315 [Temperature Anomaly in the simulation where the wind-front angle is 315 degree (K)]; TNF [Temperature Anomaly in the simulation outside a frontal zone (K)]; W0 [Vertical velocity in the simulation where the wind-front angle is 0 degree (m/s)]; W45 [Vertical velocity in the simulation where the wind-front angle is 45 degree (m/s)]; W90 [Vertical velocity in the simulation where the wind-front angle is 90 degree (m/s)]; W135 [Vertical velocity in the simulation where the wind-front angle is 135 degree (m/s)]; W180 [Vertical velocity in the simulation where the wind-front angle is 180 degree (m/s)]; W225 [Vertical velocity in the simulation where the wind-front angle is 225 degree (m/s)]; W270 [Vertical velocity in the simulation where the wind-front angle is 270 degree (m/s)]; W315 [Vertical velocity in the simulation where the wind-front angle is 315 degree (m/s)]; WNF [Vertical velocity in the simulation outside a frontal zone (m/s)]; x [Grids in the cross-gradient direction (m)]; y [Grids in the along-front direction (m)]. The turbulence statistic files contain the data to produce the horizontally and temporally averaged vertical profiles (statistics) of ageostrophic velocities, temperature, and velocity variances. The file “his_ek.nc” includes statistics for simulations without the effects of surface gravity waves, while “his_wv.nc” contains statistics for simulations including the effect of surface gravity waves. The parameters included are: z [Depth (m)]; beta_wf [Wind-front condition]; theta [Temperature profiles]; u [Ageostrophic current in x direction (m/s)]; v [Ageostrophic current in y direction (m/s)]; u2 [Horizontal velocity variance in x direction (m^2/s^2)]; v2 [Horizontal velocity variance in y direction (m^2/s^2)]; w2 [Vertical velocity variance (m^2/s^2)]. Please note that the mean w is zero so is not in the NetCDF file. Each variable has two dimensions: the first dimension is depth (z) containing 61 data points, and the second dimension represents the 14 different model setups that represent a specific wind-front angle under a specific domain size. The dataset also includes a readme text file (README4NCFILE.txt) describing the variables and fourteen different model setups for wind-front conditions. Please note that except for the variables defining the axes, the variables are named in a format of {type of variable} + {wind-front angle}. A letter T indicates temperature, while a letter w indicates vertical velocity.

Methods:

The results presented in this dataset were obtained using the National Center for Atmospheric Research Large Eddy Simulation (NCAR-LES) model (Sullivan and McWilliams 2010). Two groups of simulations, with (ins_wv.nc) or without waves (ins_ek.nc), were conducted. In each group of simulations, the angle between wind/wave and front is systematically varied. Furthermore, the simulations were conducted in a big domain and a small domain, respectively. The big domain resolves submesoscale eddies develop while the small one does not. Details of model configuration are available in the associated publication Yuan and Liang., 2021.

Provenance and Historical References:

Sullivan, P. P., & McWilliams, J. C. (2010). Dynamics of Winds and Currents Coupled to Surface Waves. Annual Review of Fluid Mechanics, 42(1), 19–42. doi:10.1146/annurev-fluid-121108-145541

Individual Files: