AeroBulk is a package/library that gathers state-of-the-art
aerodynamic bulk formulae algorithms used to estimate turbulent air-sea
fluxes in an efficient and unified way. These turbulent fluxes are wind
stress, evaporation (latent heat flux) and sensible heat flux, they are
needed as part of the surface boundary conditions of OGCMs, AGCMs and in
the coupling interface of Earth Systems.
AeroBulk relies on bulk formulae to compute turbulent air-sea fluxes from
the sea surface temperature, wind speed, and air temperature and specific
humidity.
In AeroBulk, 4 state-of-the-art algorithms are available to compute the
drag, sensible heat and moisture transfer coefficients (C
_{D},
C
_{H} and C
_{E}) used in the bulk formulaes:
In the COARE and ECMWF algorithms, a cool-skin/warm layer scheme is
included and can be activated if the input sea-surface temperature is the
bulk SST (measured a few tenths of meters below the surface). Activation
of these cool-skin/warm layer schemes requires the surface downwelling shortwave
and longwave radiative flux components to be provided.
The NCAR algorithm is to be used only with the bulk SST.
Beside bulk algorithms AeroBulk also provides a variety of functions to
accurately estimate relevant atmospheric variable such as density of air,
different expressions of the humidity of air, viscosity of air, specific
humidity at saturation, Monin-Obukhov length, wind gustiness, etc...
The focus in AeroBulk is readability, efficiency and portability towards
either modern GCMs (Fortran 90, set of modules and a library).
> Obtaining AeroBulk
The AeroBulk project is hosted on GitHub:
https://github.com/brodeau/aerobulk/
You can download the code via git:
git clone https://github.com/brodeau/aerobulk.git
or via subversion:
svn co https://github.com/brodeau/aerobulk.git/trunk aerobulk
> Computing transfer coefficients with AeroBulk
In AeroBulk, 3 different routines are available to compute the bulk
transfer (
a.k.a exchange)
coefficients C
_{D}, C
_{H} and C
_{E}.
Beside computing the transfer coefficients, these routines adjust air
temperature and humidity from height
z_{t} to the reference
height (wind)
z_{u}. They also return the bulk wind speed,
which is the scalar wind speed at height
z_{u} with the
potential inclusion of a gustiness contribution (in calm and unstable
conditions).
> Computing turbulent fluxes with AeroBulk
AeroBulk can also directly compute the 3 turbulent fluxes
with the routine
aerobulk_model() of module
mod_aerobulk (mod_aerobulk.f90):
PROGRAM TEST_FLUX
USE mod_aerobulk
...
CALL AEROBULK_MODEL( calgo, zt, zu, sst, t_zt, q_zt, U_zu, V_zu, SLP, &
& Qe, Qh, Tau_x, Tau_y &
& [, Niter=N, rad_sw=Rsw, rad_lw=Rlw] )
...
END PROGRAM TEST_FLUX
INPUT ARGUMENTS:
- calgo: (String) algorithm to use (coare/coare35/ncar/ecmwf)
- zt : (Sc,real) height for temperature and spec. hum. of air [m]
- zu : (Sc,real) height for wind speed (generally 10m) [m]
- sst : (2D,real) SST [K]
- t_zt : (2D,real) potential air temperature at zt [K]
- q_zt : (2D,real) specific humidity of air at zt [kg/kg]
- U_zu : (2D,real) zonal scalar wind speed at 10m [m/s]
- V_zu : (2D,real) meridional scalar wind speed at 10m [m/s]
- SLP : (2D,real) sea-level pressure [Pa]
[ OPTIONAL INPUT ARGUMENT: ]
- Niter: (Sc,int) number of iterations (default is 4)
- rad_sw: (2D,real) downw. shortwave rad. at surface (>0) [W/m^2]
- rad_lw: (2D,real)downw. longwave rad. at surface (>0) [W/m^2]
(The presence of rad_sw and rad_sw triggers the use of the Cool-Skin
Warm-Layer parameterization with COARE* and ECMWF algorithms)
OUTPUT ARGUMENTS:
- Qe : (2D,real) latent heat flux [W/m^2]
- Qh : (2D,real) sensible heat flux [W/m^2]
- Tau_x : (2D,real) zonal wind stress [N/m^2]
- Tau_y : (2D,real) meridional wind stress [N/m^2]
Example of a call, using COARE 3.0 algorithm with cool-skin warm-layer
parameterization and 10 iterations:
CALL AEROBULK_MODEL( 'coare', 2., 10., sst, t_zt, q_zt, U_zu, V_zu, SLP, &
& Qe, Qh, Tau_x, Tau_y, &
& Niter=10, rad_sw=Rsw, rad_lw=Rlw )
> Computing atmospheric state variables with AeroBulk
A selection of useful functions to estimate some atmospheric state
variables of the marine boundary layer are available in the
module
mod_thermo (mod_thermo.f90).
Example for computing SSQ of Eq.(1) out of the SST and the SLP:
PROGRAM TEST_THERMO
USE mod_const
USE mod_thermo
...
SSQ(:,:) = 0.98*q_sat(SST, SLP)
...
END PROGRAM TEST_THERMO
> Acknowledging AeroBulk
To acknowledge/reference AeroBulk in your scientific work, please
cite:
Brodeau, L., B. Barnier, S. Gulev, and C. Woods, 2017:
Climatologically
significant effects of some approximations in the bulk parameterizations of
turbulent air-sea fluxes. J. Phys. Oceanogr., 47 (1),
5–28, 10.1175/JPO-D-16-0169.1.
[ DOI ]