# Adjusting specular versus diffuse surfaces

**URL:** <https://forums.jcsda.org/t/adjusting-specular-versus-diffuse-surfaces/420>\
**Category:** CRTM\
**Created:** [November 29, 2022, 8:12pm UTC](https://forums.jcsda.org/t/adjusting-specular-versus-diffuse-surfaces/420 "2022-11-29T20:12:37Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![EmilyCMorgan](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/emilycmorgan/32/172_2.png) [@EmilyCMorgan](https://forums.jcsda.org/u/EmilyCMorgan)\
**Post date:** [November 29, 2022, 8:12pm UTC](https://forums.jcsda.org/t/adjusting-specular-versus-diffuse-surfaces/420/1 "2022-11-29T20:12:37Z")

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For those using CRTM (v2.4.1 develop) in conjunction with other software but not within the JEDI framework, what is the accepted highest-level method for adjusting whether a given surface (ocean/snow/etc) is to be treated as “specular” or otherwise diffuse? I am using CRTM v2.4.1 in the MiRS (Microwave Integrated Retrieval System) testbed and must have only ocean surfaces treated as specular.

in ./src/RTSolution/CRTM\_RTSolution\_Define.f90, there is the following:

```auto
! Internal variables. Users do not need to worry about these.
LOGICAL :: Scattering_Flag = .TRUE.

```

and in ./src/RTSolution/Common\_RTSolution.f90 there is:

```auto
    ! Determine the surface emission behavior
    ! By default, surface is SPECULAR.
    RTV%Diffuse_Surface = .FALSE.

```

Do either of these need to be adjusted?

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<div class="post-metadata">

**Author:** ![StegmannJCSDA](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/stegmannjcsda/32/53_2.png) [@StegmannJCSDA](https://forums.jcsda.org/u/StegmannJCSDA)\
**Post date:** [December 1, 2022, 12:31am UTC](https://forums.jcsda.org/t/adjusting-specular-versus-diffuse-surfaces/420/2 "2022-12-01T00:31:30Z")

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Hi @EmilyCMorgan. I haven’t looked into this yet, but it looks like `Assign_Common_Input` is the right place to adjust `RTV%Diffuse_Surface`.

One could check if:

```nohighlight
TRIM(Surface%SURFACE_TYPE_NAME) == 'Water'

```

to set

```nohighlight
RTV%Diffuse_Surface = .FALSE.

```

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<div class="post-metadata">

**Author:** ![EmilyCMorgan](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/emilycmorgan/32/172_2.png) [@EmilyCMorgan](https://forums.jcsda.org/u/EmilyCMorgan)\
**Post date:** [December 6, 2022, 7:10pm UTC](https://forums.jcsda.org/t/adjusting-specular-versus-diffuse-surfaces/420/3 "2022-12-06T19:10:51Z")

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Perfect, this will work. I’ll put in a logic test in `src/RTSolution/Common_RTSolution.f90` and should be good to go. Thank you!