Fortran module for Met Office scatwind neutral wind forward operator. More...
Data Types | |
| type | ufo_scatwind_neutralmetoffice |
| Fortran derived type for neutral wind. More... | |
Functions/Subroutines | |
| subroutine | ufo_scatwind_neutralmetoffice_setup (self, f_conf) |
| subroutine | ufo_scatwind_neutralmetoffice_simobs (self, geovals, obss, nvars, nlocs, hofx) |
| Neutral wind forward operator for the Met Office system. More... | |
| subroutine | ops_scatwind_forwardmodel (za, u, v, ustr, oblen, seaice, orog, ycalc, cdr10) |
| Scatterometer forward model. More... | |
| subroutine | ops_scatwind_phi_m_sea (recip_l_mo, z_uv, z0m, phi_m) |
| Calculate the integrated froms of the Monin-Obukhov stability functions for surface exchanges. More... | |
Variables | |
| character(len=maxvarlen), dimension(7), parameter | geovars_default = (/ var_u, var_v, var_zi, var_sfc_ifrac, var_sfc_geomz, var_sea_fric_vel, var_obk_length /) |
Detailed Description
Fortran module for Met Office scatwind neutral wind forward operator.
This code introduces the Met Office observation operator for scatterometer wind data. We assimilate the data as a "neutral" 10m wind, i.e. where the effects of atmospheric stability are neglected. For each observation we calculate the momentum roughness length using the Charnock relation. We then calculate the Monin-Obukhov stability function for momentum, integrated to the model's lowest wind level. The calculations are dependant upon on whether we have stable or unstable conditions according to the Obukhov Length. The neutral 10m wind components are then calculated from the lowest model level winds.
- Date
- 22/12/2020: Created
Function/Subroutine Documentation
◆ ops_scatwind_forwardmodel()
|
private |
Scatterometer forward model.
The main steps are as follows:
- For each observation we calculate the momentum roughness length using the Charnock relation (Charnock, 1955) modified to include low-wind conditions (Smith, 1988):
\[ z_{0m(sea)} = \frac{0.11\nu}{1.0 \times 10^{-5} + u_*} + \alpha_{ch} \frac{u_*^2}{g} \]
where \(\nu = 14 \times 10^{-6}\) ms-1 is the dynamic viscosity of air, \(u_{*}\) is the friction velocity, \(\alpha_{ch} =0.018\) is the charnock parameter, and \(g\) is the acceleration due to gravity. - Call a subroutine to calculate the Monin-Obukhov stability function for momentum integrated to the lowest model level, \(\Phi_{m}\). The calculations are dependant upon on whether we have stable or unstable conditions according to the Obukhov Length, \(L\).
- The neutral 10m wind components, \(v_{10n}\) are then calculated from the lowest model level winds, \(v_1\), as
\[ \textbf{v}_{10n}=\frac{\ln\left(\left(10+z_{0m}\right)/z_{0m}\right)} {\Phi_m\left(L,z_1+z_{0m},z_{0m}\right)} \textbf{v}_1 \]
References:
Charnock, H. (1955). Wind stress on a water surface. Quart. J. Royal Meteorol. Soc., 81, 639-640. Smith, R. N. B. (1988). Coefficient for sea surface wind stress, heat flux and wind profiles as a function of wind speed and temperature. J. Geophys. Res., 93, 15467-15472.
- Date
- 22/12/2020: Created
- Parameters
-
[in] za heights of rho levs [in] u Model eastward wind profile [in] v Model northward wind profile [in] ustr Model friction velocity [in] oblen Model obukhov length [in] seaice Model sea ice fraction [in] orog Model orography [in,out] ycalc Model equivalent of the obs [in,out] cdr10 10m interpolation coefficients
Definition at line 201 of file ufo_scatwind_neutralmetoffice_mod.F90.
◆ ops_scatwind_phi_m_sea()
| subroutine ufo_scatwind_neutralmetoffice_mod::ops_scatwind_phi_m_sea | ( | real, intent(in) | recip_l_mo, |
| real, intent(in) | z_uv, | ||
| real, intent(in) | z0m, | ||
| real, intent(out) | phi_m | ||
| ) |
Calculate the integrated froms of the Monin-Obukhov stability functions for surface exchanges.
The main steps are as follows:
- In neutral conditions we have the logarithmic profile:
\[ \Phi_{mn} = \ln\left(\frac{z_1 + z_{0m}}{z_{0m}}\right) \]
- In stable conditions the stability functions of Beljaars and Holtslag (1991) are used:
\[ \Phi_{m} = \Phi_{mn} + a\left(\zeta_1 - \zeta_{0m}\right) + b\left( \left(\zeta_1 - \frac{c}{d}\right) \exp\left(-d\zeta_1\right) - \left(\zeta_{0m} - \frac{c}{d}\right) \exp\left(-d\zeta_{0m}\right) \right) \]
with \(\zeta_1=(z_1+z_{0m})/L\), \(\zeta_{0m}=z_{0m}/L\), and a=1, b=2/3, c=5, d=0.35. - In unstable conditions the Dyer and Hicks forms (Dyer, 1974) are used:
\[ \Phi_{m} = \Phi_{mn} - 2\ln\left(\frac{1+X_1}{1+X_0}\right) - \ln\left(\frac{1+X_1^2}{1+X_0^2}\right) + 2\left(\tan^{-1}(X_1) - \tan^{-1}(X_0)\right) \]
with \(X_1=(1-16\zeta_1)^{1/4}\) and \(X_0=(1-16\zeta_{0m})^{1/4}\) and
References:
Beljaars, A. C. M. and Holtslag, A. A. M. (1991). Flux parameterisation over land surfaces for atmospheric models. J. Appl. Meteor., 30, 327-341.
Dyer, A. J., 1974: A review of flux-profile relationships. Bound. Layer Meteor., 7, 363-372.
- Date
- 22/12/2020: Created
- Parameters
-
[in] recip_l_mo Reciprocal of Monin-Obukhov length (m^-1). [in] z_uv Height of wind level above roughness height(m). [in] z0m Roughness length for momentum (m). [out] phi_m Stability function for momentum.
Definition at line 402 of file ufo_scatwind_neutralmetoffice_mod.F90.
◆ ufo_scatwind_neutralmetoffice_setup()
|
private |
Definition at line 61 of file ufo_scatwind_neutralmetoffice_mod.F90.
◆ ufo_scatwind_neutralmetoffice_simobs()
| subroutine ufo_scatwind_neutralmetoffice_mod::ufo_scatwind_neutralmetoffice_simobs | ( | class(ufo_scatwind_neutralmetoffice), intent(in) | self, |
| type(ufo_geovals), intent(in) | geovals, | ||
| type(c_ptr), intent(in), value | obss, | ||
| integer, intent(in) | nvars, | ||
| integer, intent(in) | nlocs, | ||
| real(c_double), dimension(nvars, nlocs), intent(inout) | hofx | ||
| ) |
Neutral wind forward operator for the Met Office system.
- Date
- 22/12/2020: Created
- Parameters
-
[in] self The object in which this operator is contained [in] nlocs The number of variables and locations [in] geovals The model values, interpolated to the obsevation locations [in,out] hofx The output model equivalent of the observations [in] obss The observations, and meta-data for those observations
Definition at line 79 of file ufo_scatwind_neutralmetoffice_mod.F90.
Variable Documentation
◆ geovars_default
| character(len=maxvarlen), dimension(7), parameter ufo_scatwind_neutralmetoffice_mod::geovars_default = (/ var_u, var_v, var_zi, var_sfc_ifrac, var_sfc_geomz, var_sea_fric_vel, var_obk_length /) |
Definition at line 48 of file ufo_scatwind_neutralmetoffice_mod.F90.
