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Modification of momentum roughness length over ice in the surface layer scheme #808

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Merged
climbfuji merged 2 commits into from
Dec 23, 2021
+10 −8
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Modification of momentum roughness length over ice in the surface layer scheme #808

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Modification of momentum roughness length over ice in the surface lay…
wzzheng90 Dec 11, 2021
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Modification of momentum roughness length over ice in the surface lay…
wzzheng90 Dec 15, 2021
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18 changes: 10 additions & 8 deletions physics/sfc_diff.f
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Original file line number Diff line number Diff line change
Expand Up @@ -40,8 +40,8 @@ end subroutine sfc_diff_finalize
!! in Zeng et al. (1998) \cite zeng_et_al_1998).
!! - Calculate Zeng's momentum roughness length formulation over land and sea ice.
!! - Calculate the new vegetation-dependent formulation of thermal roughness length
!! (Zheng et al.(2009) \cite zheng_et_al_2009).
!! Zheng et al. (2009) \cite zheng_et_al_2009 proposed a new formulation on
!! (Zheng et al.(2012) \cite zheng_et_al_2012).
!! Zheng et al. (2012) \cite zheng_et_al_2012 proposed a new formulation on
!! \f$ln(Z_{0m}^,/Z_{0t})\f$ as follows:
!! \f[
!! ln(Z_{0m}^,/Z_{0t})=(1-GVF)^2C_{zil}k(u*Z_{0g}/\nu)^{0.5}
Expand Down Expand Up @@ -305,12 +305,14 @@ subroutine sfc_diff_run (im,rvrdm1,eps,epsm1,grav, & !intent(in)
tem2 = tem1 * tem1
tem1 = one - tem2

if( ivegsrc == 1 ) then

z0max = exp( tem2*log01 + tem1*log(z0max) )
elseif (ivegsrc == 2 ) then
z0max = exp( tem2*log01 + tem1*log(z0max) )
endif
! Removed the following lines by W. Zheng, for effective z0m (z0max) is applied only
! for land.
!wz if( ivegsrc == 1 ) then
!wz
!wz z0max = exp( tem2*log01 + tem1*log(z0max) )
!wz elseif (ivegsrc == 2 ) then
!wz z0max = exp( tem2*log01 + tem1*log(z0max) )
!wz endif
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@SamuelTrahanNOAA SamuelTrahanNOAA Dec 14, 2021

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Commented-out code should only be in the repository for a good reason. Please add a comment above the "!wz" lines giving the context. For example: what the code did, why it was removed, and what it should be replaced with. (This can be short, and only understandable by a subject matter expert.)

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@wzzheng90 wzzheng90 Dec 15, 2021

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Good point! I added a comment before "!wz" lines. Thanks!!
In fact, these lines are used to calculate the effective momentum roughness length z0m proposed by Zheng et al.
(2012, https://doi.org/10.1029/2011JD015901). However, the effective z0m formulation is applied only for land, rather than for ice.
Moreover, since "shdmax" is zero over ice, these lines of code yield that z0max is actually 0.01 which is the momentum roughness length over bare soil (z0g) and not related to the ice momentum roughness length.

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@SamuelTrahanNOAA SamuelTrahanNOAA Dec 16, 2021

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Looks good to me.


z0max = max(z0max, zmin)

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