Dear Shaofei Wang,
There is no difference between polarisations when it comes to the rule
of e+r=1. So when it is valid for V and H, it is also value for e.g 45
deg and left-hand circular. Notice "when", as the rule is not fully
valid for all cases. The rule is valid when you have surface scattering
(which is true for water surfaces), but not necessarily when you have
volume scattering (such as snow).
In addition, FASTEM (at least in some versions) deviate from e+r=1, as a
way to adjust for non-specular reflections. If this affects U and V, I
have no idea.
Bye,
Patrick
On 2023-02-24 10:13, Shaofei Wang wrote:
Dear Patrick,
Thank you very much for your reply!
I'm sorry that I can't make some suggestions for modifying surfaceFASTEM
for the short time, since I'm a beginner in Vector Radiation Transfer.
In addition, I would like to ask whether e+r≈1 is true for U and V
stokes parameters.
Best regards,
Shaofei Wang
---- Replied Message ----
From Patrick Eriksson<patrick.eriks...@chalmers.se>
<mailto:patrick.eriks...@chalmers.se>
Date 2/23/2023 21:29
To Shaofei Wang<wangshaofei...@163.com> ,
<mailto:wangshaofei...@163.com>
arts_users.mi@lists.uni-hamburg.de<arts_users.mi@lists.uni-hamburg.de>
<mailto:arts_users.mi@lists.uni-hamburg.de>
Subject Re: [arts-users] Question about Fastem
Dear Shaofei Wang,
I had a quick look at the code, and yes FASTEM values matching U and V
are not used. Despite I stand as author for the FASTEM methods, I can
answer why we left it like this. There are several possibilities:
1. It was left to be fixed later.
2. We were unsure about how to map those values to surface_rmatrix.
3. We did not trust FASTEM for those values
I think it was a combination of 2 and 3.
If you have looked into this, do you have a suggestion for how to modify
surfaceFASTEM to fix this? Please notice that Section 6.9.3 in ARTS
theory guide deals with this. Notice especially Eq 6.79. If you can
relate what FASTEM outputs for U and V to that equation, it would be
easy to adopt the code.
Bye,
Patrick
On 2023-02-23 13:28, Shaofei Wang wrote:
Hi all,
Fastem provided by ARTS can calculate the sea emissivities of H, V, the
third Stokes component, and the fourth Stokes component.
However, the source code of WSM surfaceFastem shows that the reflection
coefficients of the third and the fourth stokes components are equal to
(rv+rh)/2, which confuses me.
Why are they not equal to the r3/r4 calculated by the Fastem? For
surfaceFastem, surface_rmatrix seems to be calculated in the same
way as
when only rv/rh is available (if I understand correctly)
Best regards,
Shaofei Wang
