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Tidal angular frequency has units [rad s-1] (mom-ocean#764)
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* Tidal angular frequency has units [rad s-1]

Tidal frequencies are always angular frequencies to simplify applying
sine and cosine.  These have MKS units [rad s-1] but they are all
currently listed as [s-1].

Updated dOxygen comments for variables, e.g. [T-1 ~> s-1] becomes
[rad T-1 ~> rad s-1].  Updated get_param units. e.g. units="s-1"
becomes units="rad s-1".

No answers are changed, but the logged parameter units are different.

There are frequencies in MOM_internal_tides.F90 but these have not
been updated because they may be specified incorrectly.  They are
used as if they are [T-1] but they are calculated as 2PI/period [rad T-1].

  real, allocatable, dimension(:) :: frequency  !< The frequency of each band [T-1 ~> s-1].

  real    :: period             ! A tidal period read from namelist [T ~> s]

  ! The periods of the tidal constituents for internal tides raytracing
  call read_param(param_file, "TIDAL_PERIODS", periods)

  do fr=1,num_freq
    period = US%s_to_T*extract_real(periods, " ,", fr, 0.)
    CS%frequency(fr) = 8.0*atan(1.0)/period
  enddo

All MOM6-examples cases have INTERNAL_TIDES=False and so can't
resolve this issue.

* fixed too-long line
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@awallcraft
awallcraft authored Dec 9, 2024
1 parent f920c1a commit 78a7936
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Showing 4 changed files with 13 additions and 11 deletions.
6 changes: 3 additions & 3 deletions src/core/MOM_barotropic.F90
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Expand Up @@ -5270,7 +5270,7 @@ subroutine register_barotropic_restarts(HI, GV, US, param_file, CS, restart_CS)
character(len=40) :: mdl = "MOM_barotropic" ! This module's name.
integer :: isd, ied, jsd, jed, IsdB, IedB, JsdB, JedB
real :: am2, ak1 !< Bandwidth parameters of the M2 and K1 streaming filters [nondim]
real :: om2, ok1 !< Target frequencies of the M2 and K1 streaming filters [T-1 ~> s-1]
real :: om2, ok1 !< Target frequencies of the M2 and K1 streaming filters [rad T-1 ~> rad s-1]

isd = HI%isd ; ied = HI%ied ; jsd = HI%jsd ; jed = HI%jed
IsdB = HI%IsdB ; IedB = HI%IedB ; JsdB = HI%JsdB ; JedB = HI%JedB
Expand Down Expand Up @@ -5301,13 +5301,13 @@ subroutine register_barotropic_restarts(HI, GV, US, param_file, CS, restart_CS)
"Frequency of the M2 tidal constituent. "//&
"This is only used if TIDES and TIDE_M2"// &
" are true, or if OBC_TIDE_N_CONSTITUENTS > 0 and M2"// &
" is in OBC_TIDE_CONSTITUENTS.", units="s-1", default=tidal_frequency("M2"), &
" is in OBC_TIDE_CONSTITUENTS.", units="rad s-1", default=tidal_frequency("M2"), &
scale=US%T_to_s, do_not_log=.true.)
call get_param(param_file, mdl, "TIDE_K1_FREQ", ok1, &
"Frequency of the K1 tidal constituent. "//&
"This is only used if TIDES and TIDE_K1"// &
" are true, or if OBC_TIDE_N_CONSTITUENTS > 0 and K1"// &
" is in OBC_TIDE_CONSTITUENTS.", units="s-1", default=tidal_frequency("K1"), &
" is in OBC_TIDE_CONSTITUENTS.", units="rad s-1", default=tidal_frequency("K1"), &
scale=US%T_to_s, do_not_log=.true.)

ALLOC_(CS%ubtav(IsdB:IedB,jsd:jed)) ; CS%ubtav(:,:) = 0.0
Expand Down
5 changes: 3 additions & 2 deletions src/core/MOM_open_boundary.F90
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Expand Up @@ -320,7 +320,8 @@ module MOM_open_boundary
logical :: add_tide_constituents = .false. !< If true, add tidal constituents to the boundary elevation
!! and velocity. Will be set to true if n_tide_constituents > 0.
character(len=2), allocatable, dimension(:) :: tide_names !< Names of tidal constituents to add to the boundary data.
real, allocatable, dimension(:) :: tide_frequencies !< Angular frequencies of chosen tidal constituents [T-1 ~> s-1].
real, allocatable, dimension(:) :: tide_frequencies !< Angular frequencies of chosen tidal
!! constituents [rad T-1 ~> rad s-1].
real, allocatable, dimension(:) :: tide_eq_phases !< Equilibrium phases of chosen tidal constituents [rad].
real, allocatable, dimension(:) :: tide_fn !< Amplitude modulation of boundary tides by nodal cycle [nondim].
real, allocatable, dimension(:) :: tide_un !< Phase modulation of boundary tides by nodal cycle [rad].
Expand Down Expand Up @@ -1234,7 +1235,7 @@ subroutine initialize_obc_tides(OBC, US, param_file)
"This is only used if TIDES and TIDE_"//trim(OBC%tide_names(c))// &
" are true, or if OBC_TIDE_N_CONSTITUENTS > 0 and "//trim(OBC%tide_names(c))//&
" is in OBC_TIDE_CONSTITUENTS.", &
units="s-1", default=tidal_frequency(trim(OBC%tide_names(c))), scale=US%T_to_s)
units="rad s-1", default=tidal_frequency(trim(OBC%tide_names(c))), scale=US%T_to_s)

! Find equilibrium phase if needed
if (OBC%add_eq_phase) then
Expand Down
4 changes: 2 additions & 2 deletions src/parameterizations/lateral/MOM_streaming_filter.F90
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Expand Up @@ -15,7 +15,7 @@ module MOM_streaming_filter
!> The control structure for storing the filter infomation of a particular field
type, public :: Filter_CS ; private
real :: a, & !< Parameter that determines the bandwidth [nondim]
om, & !< Target frequency of the filter [T-1 ~> s-1]
om, & !< Target frequency of the filter [rad T-1 ~> rad s-1]
old_time = -1.0 !< The time of the previous accumulating step [T ~> s]
real, allocatable, dimension(:,:) :: s1, & !< Dummy variable [A]
u1 !< Filtered data [A]
Expand All @@ -29,7 +29,7 @@ module MOM_streaming_filter
!> This subroutine registers each of the fields to be filtered.
subroutine Filt_register(a, om, grid, HI, CS)
real, intent(in) :: a !< Parameter that determines the bandwidth [nondim]
real, intent(in) :: om !< Target frequency of the filter [T-1 ~> s-1]
real, intent(in) :: om !< Target frequency of the filter [rad T-1 ~> rad s-1]
character(len=*), intent(in) :: grid !< Horizontal grid location: h, u, or v
type(hor_index_type), intent(in) :: HI !< Horizontal index type structure
type(Filter_CS), intent(out) :: CS !< Control structure for the current field
Expand Down
9 changes: 5 additions & 4 deletions src/parameterizations/lateral/MOM_tidal_forcing.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ module MOM_tidal_forcing
!! and bottom geopotential anomalies [nondim].
integer :: nc !< The number of tidal constituents in use.
real, dimension(MAX_CONSTITUENTS) :: &
freq, & !< The frequency of a tidal constituent [T-1 ~> s-1].
freq, & !< The frequency of a tidal constituent [rad T-1 ~> rad s-1].
phase0, & !< The phase of a tidal constituent at time 0 [rad].
amp, & !< The amplitude of a tidal constituent at time 0 [Z ~> m].
love_no !< The Love number of a tidal constituent at time 0 [nondim].
Expand Down Expand Up @@ -151,7 +151,7 @@ end function eq_phase
!! Values used here are from previous versions of MOM.
function tidal_frequency(constit)
character (len=2), intent(in) :: constit !> Constituent to look up
real :: tidal_frequency !> Angular frequency [s-1]
real :: tidal_frequency !> Angular frequency [rad s-1]

select case (constit)
case ("M2")
Expand Down Expand Up @@ -246,7 +246,7 @@ subroutine tidal_forcing_init(Time, G, US, param_file, CS, HA_CS)
phase, & ! The phase of some tidal constituent [radians].
lat_rad, lon_rad ! Latitudes and longitudes of h-points [radians].
real :: deg_to_rad ! A conversion factor from degrees to radians [radian degree-1]
real, dimension(MAX_CONSTITUENTS) :: freq_def ! Default frequency for each tidal constituent [s-1]
real, dimension(MAX_CONSTITUENTS) :: freq_def ! Default frequency for each tidal constituent [rad s-1]
real, dimension(MAX_CONSTITUENTS) :: phase0_def ! Default reference phase for each tidal constituent [rad]
real, dimension(MAX_CONSTITUENTS) :: amp_def ! Default amplitude for each tidal constituent [m]
real, dimension(MAX_CONSTITUENTS) :: love_def ! Default love number for each constituent [nondim]
Expand Down Expand Up @@ -480,7 +480,8 @@ subroutine tidal_forcing_init(Time, G, US, param_file, CS, HA_CS)
"Frequency of the "//trim(CS%const_name(c))//" tidal constituent. "//&
"This is only used if TIDES and TIDE_"//trim(CS%const_name(c))// &
" are true, or if OBC_TIDE_N_CONSTITUENTS > 0 and "//trim(CS%const_name(c))// &
" is in OBC_TIDE_CONSTITUENTS.", units="s-1", default=freq_def(c), scale=US%T_to_s)
" is in OBC_TIDE_CONSTITUENTS.", units="rad s-1", default=freq_def(c), &
scale=US%T_to_s)
call get_param(param_file, mdl, "TIDE_"//trim(CS%const_name(c))//"_AMP", CS%amp(c), &
"Amplitude of the "//trim(CS%const_name(c))//" tidal constituent. "//&
"This is only used if TIDES and TIDE_"//trim(CS%const_name(c))// &
Expand Down

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