DOI: 10.5281/zenodo.17728454
title: The nontraditional Coriolis terms and trade-wind cumuli

description: These data are large eddy simulations of the ATEX observations using SAM6.11.9 (http://rossby.msrc.sunysb.edu/SAM/) with and without the nontraditional Coriolis terms (NCTs)

Deviations from the original simulations to better match the observations:

(1) The latitude is set to 14.44 degrees North.

(2) The subsidence speed is set to 7.15 mm/s at 1650 m and above, linearly decreases to 6.36 mm/s at 1050 m, and then linearly decreases to 0 at the surface.

(3) The clear-sky radiative cooling rate is set to 2.2097e-05 K/s at 1650 m and below and linearly increases to 2.3166e-05 K/s at 3000 m.

(4) The horizonal advective cooling rate is set to 1.2652e-05 K/s at 1400 m and below and linearly decreases to 0 at 1650 m.

(5) The horizonal advective drying rate is set to 1.58e-08 1/s at the surface and linearly decreases to 0 at 1050 m.

(6) The initial wind profile is set to [u,v] = [-11 m/s + 0.003/s*z,0] to match the observed geostrophic wind profile, which is almost east-west unlike the original setting.

(7) The integration time is extended from 8 hours to 8 days, including a spinup where the forcing linearly increases from 0 to as specified in (2) to (5).

Changes to SAM6.11.9 to better match the original simulations (Stevens et al., 2001)

SRC/domain.f90

Use 6464150 grids.

SRC/forcing.f90

Implement dosfcforcing without the necessity of (time.gt.timelargescale).

SRC/rad_simple.f90

Set the longwave cloud forcing to 57 W/m^2 at the top and absorption coefficient to 105 m/kg.

SRC/setgrid.f90

For the Coriolis terms (fcor and fcorz), set the rotation period to 86165 s instead of 86400 s.

SRC/setperturb.f90

Set the initial perturbation layer top to 810 m in case(5).

SRC/surface.f90

Implement bulk aerodynamic formula for heat and moisture fluxes while prescribing momentum flux if (.not.SFC_FLX_FXD.and.SFC_TAU_FXD).

Reference for simulations:

Stevens, B., Ackerman, A. S., Albrecht, B. A., Brown, A. R., Chlond, A., Cuxart, J., ... & Stevens, D. E. (2001). Simulations of trade wind cumuli under a strong inversion. Journal of the Atmospheric Sciences, 58(14), 1870-1891.

Reference for observations:

Augstein, E., Riehl, H., Ostapoff, F., & Wagner, V. (1973). Mass and energy transports in an undisturbed Atlantic trade-wind flow. Monthly Weather Review, 101(2), 101-111.

Files and variables

File: ATEX_NCT.nml

Description: Namelist of a simulation with the NCTs

File: ATEX_NCT.nc

Description: Output of the simulation with the NCTs

File: ATEX_TCT.nml

Description: Namelist of a simulation without the NCTs

File: ATEX_TCT.nc

Description: Output of the simulation without the NCTs

File: ATEX_NCT_westerly.nml

Description: Namelist of a simulation with the NCTs with the prevailing winds flipped to westerlies

File: ATEX_NCT_westerly.nc

Description: Output of the simulation with the NCTs with the prevailing winds flipped to westerlies

File: ATEX_TCT_120.nml

Description: Namelist of a simulation without the NCTs (cloud absorption coefficient: 120 m/kg)

File: ATEX_TCT_120.nc

Description: Output of the simulation without the NCTs (cloud absorption coefficient: 120 m/kg)

File: ATEX_TAU_NCT.nml

Description: Namelist of a simulation with the NCTs with prescribed surface heat fluxes and diagnosed surface wind stress.

File: ATEX_TAU_NCT.nc

Description: Output of the simulation with the NCTs with prescribed surface heat fluxes and diagnosed surface wind stress.

File: ATEX_TAU_TCT.nml

Description: Namelist of a simulation without the NCTs with prescribed surface heat fluxes and diagnosed surface wind stress.

File: ATEX_TAU_TCT.nc

Description: Output of the simulation without the NCTs with prescribed surface heat fluxes and diagnosed surface wind stress.

Code/software

The *.nml files are plain text.

The *.nc files are in NetCDF format, which can be viewed with many tools. I used ncview and ncl.

ncview: Ncview 2.1.9 David W. Pierce 14 July 2019 (http://meteora.ucsd.edu:80/~pierce/ncview_home_page.html)

ncl: University Corporation for Atmospheric Research. NCAR Command Language Version 6.6.2. The use of this software is governed by a License Agreement. See http://www.ncl.ucar.edu/ for more details.