Abstract:

A series of the Larval TRANSport Lagrangian model (LTRANS) simulation for surface Lagrangian tracers in the De Soto Canyon region and to the west of the Mississippi Fan. The Lagrangian tracers are confined near the ocean surface and are advected off-line by interpolating on the particle positions the regional ocean modeling system (ROMS) hourly-averaged horizontal velocities using LTRANS v.2b.

Suggested Citation:

Daoxun Sun, Jun Choi, Guangpeng Liu & Annalisa Bracco. 2019. Simulations of surface Lagrangian tracers using the regional ocean modeling system (ROMS) velocity field in the northern Gulf of Mexico from 2016-01-29 to 2016-08-08. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-np9a-p268

Publications:

Sun, D., Bracco, A., Barkan, R., Berta, M., Dauhajre, D., Molemaker, M. J., … McWilliams, J. C. (2020). Diurnal Cycling of Submesoscale Dynamics: Lagrangian Implications in Drifter Observations and Model Simulations of the Northern Gulf of Mexico. Journal of Physical Oceanography, 50(6), 1605–1623. doi:10.1175/jpo-d-19-0241.1

Purpose:

These simulations are performed to understand the behavior of surface Lagrangian drifters and provide information about the diurnal circle in the Gulf of Mexico.

Data Parameters and Units:

Model_time (time that has passed thus far in the model, seconds); dob (date of birth of particles in seconds from model start, seconds); age (age of particles, seconds); depth (depth of particles, meters below surface); color (identification number for particle behavior or status, nondimensional; on (longitude of particles, decimal degree E); lat (latitude of particles, decimal degree N). The following eight LTRANS simulations are included: LTRANS_LR1_Feb.mat: Forced by ROMS output LR1. 22870 tracers are released over IR1 domain. Starting from Feb 1, 2016. Simulated for 356 hours. LTRANS_IR1_Feb.nc: Forced by ROMS output IR1. 22870 tracers are released over IR1 domain. Starting from Feb 1, 2016. Simulated for 360 hours. LTRANS_HR1_Feb.nc: Forced by ROMS output HR1. 19992 tracers are released over De Soto Canyon (DS) region. Starting from Feb 1, 2016. Simulated for 360 hours. LTRANS_IR2_DS_fromJan29.nc: forced by ROMS output HR1. 19992 tracers are released over DS region. Starting from Jan 29, 2016. Simulated for 720 hours. LTRANS_IR2_DS_tri_fromJan29.nc: forced by ROMS output HR1. 19992 tracers are released as 6664 triplets over DS region. Starting from Jan 29, 2016. Simulated for 720 hours. LTRANS_IR2_DS_fromJul19.nc: forced by ROMS output HR1. 19992 tracers are released over DS region. Starting from Jul 19, 2016. Simulated for 240 hours. LTRANS_IR2_DSsw_tri_fromJul19.nc: forced by ROMS output HR1. 4956 tracers are released as 1652 triplets over the 1/4th south-west portion of DS region. Starting from Jul 19, 2016. Simulated for 240 hours. LTRANS_IR2_West_tri_fromJul19.nc: forced by ROMS output HR1. 4956 tracers are released as 1652 triplets to the west of the Mississippi Fan. Starting from Jul 19, 2016. Simulated for 240 hours.

Methods:

The four sets of ROMS outputs are used as the velocity fields for LTRANS simulations: Detailed descriptions of LR1, IR1 & HR1 can be found in Barkan et al., 2017 & Choi et al., 2017. These runs are forced by CORE monthly heat fluxes, HOAPS monthly fresh-water atmospheric forcing fields, and daily varying, climatological winds build upon QuikSCAT data. An empirical diurnal cycle based on the shortwave flux is imposed. Furthermore, the Mississippi River System outflow is simulated based on monthly mean volume flux data in the LR1 run, and on daily volume fluxes reconstructed by USGS for the year 2010 in the IR1 and HR1 cases. No tidal forcing is included. Near-inertial oscillations are not captured due to the climatological wind field and the absence of tidal forcing; as a result, the diurnal cycling in Eulerian and Lagrangian dynamical quantities result only from the response of the submesoscale circulations to changes in the shortwave flux. The simulations of February 2016 is used here. LR1: the horizontal resolution is 1500 m covering the entire Gulf of Mexico and nested into a run of the North Atlantic. IR1: the horizontal resolution is 500 m covering the northern portion of the Gulf and nested onto LR1. HR1: the horizontal resolution is 150 m nested onto IR1 over the De Soto Canyon (DS) region. IR2 run covers a similar region as IR1. The horizontal resolution is 500 m. The model uses the HYCOM - NCODA (Hybrid Coordinate Ocean Model - Navy Coupled Ocean Data Assimilation) ocean prediction system as 6-hourly varying boundary conditions from January 2015 to December 2016, following a year-long spin-up. The atmospheric forcing fields are from the ERA-interim reanalysis, 6-hourly for heat and momentum and daily for freshwater (evaporation and precipitation); the Mississippi River System discharge is imposed base on the USGS daily data. Tidal forcing is neglected also in this configuration. The outputs of winter and summer months in 2016 are used.

Provenance and Historical References:

Barkan, R., McWilliams, J. C., Shchepetkin, A. F., Molemaker, M. J., Renault, L., Bracco, A., & Choi, J. (2017). Submesoscale Dynamics in the Northern Gulf of Mexico. Part I: Regional and Seasonal Characterization and the Role of River Outflow. Journal of Physical Oceanography, 47(9), 2325–2346. doi:10.1175/jpo-d-17-0035.1 Choi, J., Bracco, A., Barkan, R., Shchepetkin, A. F., McWilliams, J. C., & Molemaker, J. M. (2017). Submesoscale Dynamics in the Northern Gulf of Mexico. Part III: Lagrangian Implications. Journal of Physical Oceanography, 47(9), 2361–2376. doi:10.1175/jpo-d-17-0036.1

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