ASINTER-05_Brodeau_Advanced_Bulk

Last edition: Wikinfo(changed_ts)? by Wikinfo(changed_by)?

The PI is responsible to closely follow the progress of the action, and especially to contact NEMO project manager if the delay on preview (or review) are longer than the 2 weeks expected.

1. Summary
2. Abstract
3. Description
4. Implementation
5. Reference manual update
6. Associated test case
7. Progress
8. SETTE test
9. Review
10. MP ready

Summary

See ticket #2159 https://forge.ipsl.jussieu.fr/nemo/ticket/2159

Action	ASINTER-05_Brodeau_Advanced_Bulk
PI(S)	Laurent Brodeau @ Ocean Next
Digest	More accurate air-sea flux estimates through the implementation of a cool-skin/warm-layer parameterization in NEMO, also more advanced bulk formulae over sea-ice.
Dependencies
Expected for	December, 2019
Ticket	#2159
Branch	NEMO/branches/2019/dev_r11085_ASINTER-05_Brodeau_Advanced_Bulk
Previewer(s)
Reviewer(s)	Guillaume Samson
Link	ExtractUrl(.)?

Abstract

• 1/ Implement different state-of-the-art bulk formula parameterizations used to compute transfer coefficients (CD, CE, and CH) for estimates of turbulent air-sea fluxes:
  • a/ NCAR (previously known as "CORE", Large and Yeager, 2004,2008)
  • b/ ECMWF (IFS@ECWMF, cy45r1)
  • c/ COARE 3.0 (Fairall et al, 2003)
  • d/ COARE 3.6 (Edson et al, 2013; Fairall et al, 2019)

• 2/ Implement, when relevant, their respective cool-skin and warm-layer parameterization for better estimate of the water temperature at the air-sea interface (which is the relevant temperature to estimate heat flux to the atmosphere).
  • a/ NCAR → irrelevant
  • b/ ECMWF → cool-skin & warm-layer of ECMWF
  • c/ COARE 3.0 → cool-skin & warm-layer of COARE
  • d/ COARE 3.6 → cool-skin & warm-layer of COARE

• 3/ Improve the accuracy of various physical parameters used in the estimate of surface fluxes and previously assumed constant.

• 4/ Implement more advanced bulk parameterization for turbulent "air-ice" fluxes of momentum, heat and freshwater over sea-ice

Description

See Abstract (above) and Implementation (below).

Implementation

Modified modules aka source files

(Forked from NEMOGCM trunk at rev 11085, kept up-to-date with rev 12030 of the trunk)

• SBC/sbc_oce.F90
  • Added rhoa, public 2D array to contain the air density at z=zu [kg/m3]

• SBC/sbcblk.F90
  • Moved all the functions for air thermodynamics into a new module: SBC/sbcblk_phy.F90
  • Moved all physical parameters constants formerly declared into sbcblk.F90 into sbcblk_phy.F90 and suppressed those already declared in phycst.F90 (then using the name they have in phycst.F90 obviously...)
  • New namelist parameters to namelist's section namsbc_blk:
    • ln_skin_cs (if true: use the cool-skin parameterization if supported by selected bulk algorithm)
    • ln_skin_wl (if true: use the warm-layer parameterization if supported by selected bulk algorithm)
    • ln_humi_sph (if true: air humidity in the forcing files is specific humidity [kg/kg])
    • ln_humi_dpt (if true: air humidity in the forcing files is dew-point temperature [K])
    • ln_humi_rlh (if true: air humidity in the forcing files is relative humidity [%])
    • ln_COARE_3p6 replaces the old ln_COARE_3p5, because we upgraded from COARE 3.5 to COARE 3.6 (3.5 was intermediate and not "official").
  • 0.98 now becomes rdct_qsat_salt (into sbcblk_phy.F90)
  • Longwave radiative flux component zqlw now computed after turbulent fluxes are, because needs the updated skin temperature which comes out the turb_ecmwf (and soon turb_coare*) function
  • Corrected mistake: no rdct_qsat_salt factor for q_sat over ice! (zqi_sat)
  • Added XIOS iom_put for density of air (rho_air), and skin temperature
  • Added local arrays zqair to contain specific humidity of air at height rn_zqt
  • When ln_humi_sph=.true., zqair is simply what is read into sn_humi file (spec. hum.). When ln_humi_dpt=.true., zqair is deduced from the dew-point temperature (read into sn_humi file) and the SLP. When ln_humi_rlh=.true., zqair is deduced from the relative humidity (read into sn_humi file), air temperature, and SLP.
  • rhoa (air density at height rn_zu, declared into sbc_oce.F90) is updated once for all in blk_oce() instead of being computed their and their in different locations.

• SBC/sbcblk_algo_ecmwf.F90
  • Increased numerical stability to handle non-realistic values over land points, which caused systematic crash in old version (such as in 4.0)
  • The use of the ECMWF cool-skin/warm-layer parameterizations is triggered when namsbc_blk namelist flags ln_skin_cs/ln_skin_wl are set to .true., respectively (optional arguments Qsw, rad_lw, slp of routine turb_ecmwf must then be explicitly specified)
    • In each iteration step, estimation of solar and non-solar components of net surface heat flux is done prior to call to subroutines CS_ECMWF and WL_ECMWF (defined into SBC/sbcblk_skin_ecmwf.F90)
  • Some variables renamed for clarity, ex: sst → T_s
  • Function visc_air moved to sbcblk_phy.F90...
  • Use of function Ri_bulk() defined into SBC/sbcblk_phy.F90

• SBC/sbcblk_algo_coare.F90 is gone, it is now SBC/sbcblk_algo_coare_3p0.F90 for the sake of name-convention consistency

• SBC/sbcblk_algo_coare_3p0.F90 (ex sbcblk_algo_coare.F90)
  • Increased numerical stability to handle non-realistic values over land points, which caused systematic crash in old version (such as in 4.0)
  • The use of the COARE cool-skin/warm-layer parameterizations is triggered when namsbc_blk namelist flags ln_skin_cs/ln_skin_wl are set to .true., respectively (optional arguments Qsw, rad_lw, slp of routine turb_coare3p0 must then be explicitly specified)
    • In each iteration step, estimation of solar and non-solar components of net surface heat flux is done prior to call to subroutines CS_COARE and WL_COARE (defined into SBC/sbcblk_skin_coare.F90)
  • Some variables renamed for clarity, ex: sst → T_s
  • Function visc_air moved to sbcblk_phy.F90...
  • Use of functions One_on_L() and Ri_bulk() defined into SBC/sbcblk_phy.F90

• SBC/sbcblk_algo_coare_3p5.F90 is gone, it is now SBC/sbcblk_algo_coare_3p6.F90

• SBC/sbcblk_algo_coare_3p6.F90 (ex sbcblk_algo_coare_3p5.F90)
  • upgraded from COARE 3.5 to COARE 3.6 (3.5 was intermediate and not "official") following Fairall et al. 2019 (in prep.) and Edson et al. 2013
  • applied all improvements mentioned for SBC/sbcblk_algo_coare_3p0.F90.

• SBC/sbcblk_algo_ncar.F90
  • use of sbcblk_phy.F90 for functions virt_temp() and One_on_L()

New modules

• SBC/sbcblk_phy.F90 [ catalog of functions of some non constant physical parameters in the MBL (Marine Boundary Layer) ] → Gathers the following functions:
  • virt_temp (computes absolute/potential VIRTUAL temperature out of absolute/potential temperature and specific humidity)
  • Rho_air (computes density of air out of air temperature and spec. hum. and SLP)
  • Visc_air (computes kinematic viscosity of air out of air temperature)
  • L_vap (computes the latent heat of vaporization of water out of water temperature)
  • cp_air (computes the specific heat, aka Cp, of moist air out of specific humidity)
  • gamma_moist (computes the the adiabatic lapse-rate of moist air out of air temperature and spec. hum.)
  • One_on_L (computes 1/[Monin-Obukhov length])
  • Ri_bulk (computes the bulk Richardson number)
  • e_sat_sclr (computes "e_sat", the water vapor pressure of saturated air out of air temperature and SLP, scalar IO arguments)
  • q_sat (computes the specific humidity at saturation out of temperature of air and SLP)
  • q_air_rh (computes the specific humidity of air out of relative humidity and temperature of air and SLP)
• Because of the introduction of the cool-skin and warm-layer schemes in the "ECMWF" and "COARE" algorithms, surface heat fluxes have to be estimated (via bulk formulae) at different times and places in the code. For the sake of consistency, in order to ensure that the exact same set of bulk formulae is used each time some surface heat flux components need to be estimated, the 2 following routines have been introduced into SBC/sbcblk_phy.F90:
  • bulk_formula (computes the turbulent components of the surface heat flux, namely wind stress and latent and sensible heat fluxes, using aerodynamic bulk formulae; based on near-surface atmospheric and sea-surface states)
  • update_qnsol_tau (computes the non-solar heat flux component and the module of the wind stress based on bulk formulae, calls routine bulk_formula)

• SBC/sbcblk_skin_ecmwf.F90 [ cool-skin / warm-layer parameterization of ECMWF, contains functions CS_ECMWF (cool-skin scheme) and WL_ECMWF (warm-layer scheme), which update the value of the skin temperature out of previous guess of skin temperature, solar and non-solar components of surface heat flux and friction velocity u*] → Gathers the following subroutine:
  • CS_ECMWF cool-skin scheme
  • WL_ECMWF warm-layer scheme

• SBC/sbcblk_skin_coare.F90 [ cool-skin / warm-layer parameterization of COARE, contains functions CS_COARE (cool-skin scheme) and WL_COARE (warm-layer scheme), which update the value of the skin temperature out of previous guess of skin temperature, solar and non-solar components of surface heat flux and friction velocity u*] → Gathers the following subroutine:
  • CS_COARE cool-skin scheme
  • WL_COARE warm-layer scheme

Reference manual update

The section Bulk formulae of the chapter `Surface Boundary Condition (SBC, SAS, ISF, ICB)` is undergoing substantial improvements at the same time that all the new features introduced in this branch are being documented.

Associated test case

tests/STATION_ASF: demonstration case that mimics an in-situ station (buoy, platform) dedicated to the estimation of surface air-sea fluxes by means of the measurement of traditional meteorological surface parameters. See ​https://github.com/brodeau/aerobulk/blob/master/misc/STATION_ASF_of_NEMO/README.md for more information.

Progress

• 1/ 100% completed

• 2/ 100% completed

• 3/ 100% completed

• 4/ 0% completed

SETTE test

Passed successfully

Review

The review has been carried out by Guillaume Samson.

MP ready

Totally ready for MP 2019 in December.