# Recommendations for mass fixers in OpenIFS?

**URL:** <https://forum.ecmwf.int/t/recommendations-for-mass-fixers-in-openifs/12164>\
**Category:** OpenIFS\
**Tags:** openifs-40r1, openifs-dynamics\
**Created:** [7 July 2019 20:11 UTC](https://forum.ecmwf.int/t/recommendations-for-mass-fixers-in-openifs/12164 "2019-07-07T20:11:22Z")\
**Posts on this page:** 2\
**Page:** 2

<div class="post-metadata">

**Author:** ![Etienne\_Tourigny](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/e/50afbb/32.png) [@Etienne\_Tourigny](https://forum.ecmwf.int/u/Etienne_Tourigny)\
**Post date:** [8 May 2024 10:23 UTC](https://forum.ecmwf.int/t/recommendations-for-mass-fixers-in-openifs/12164/21 "2024-05-08T10:23:53Z")

</div>

Thanks Michail Diamantakis this is very useful! The LTRCMFMG option was suggested by Jan, we have been using LTRCMFBC without any problems using the recommendations in the linked "[Options for mass fixers in IFS](https://confluence.ecmwf.int/pages/viewpage.action?pageId=47300166)" CONFLUENCE page (which is not available to the general public, unfortunately).

I am mainly interested in GHG (specifically CO2), we have been using so far following the same page and using YGHG\_NL(1)%BETAMFBC=2 . This same page contains the following: "For example, we may use 2 for CO2, CH4 and 1 for humidity. For most cases 1 is the recommended value".&nbsp;

Is there any updated information on why using&nbsp;YGHG\_NL(1)%BETAMFBC=1.5 would be better than 2?

---

<div class="post-metadata">

**Author:** ![Michail\_Diamantakis](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/m/d2c977/32.png) [@Michail\_Diamantakis](https://forum.ecmwf.int/u/Michail_Diamantakis)\
**Post date:** [8 May 2024 10:41 UTC](https://forum.ecmwf.int/t/recommendations-for-mass-fixers-in-openifs/12164/22 "2024-05-08T10:41:24Z")

</div>

Hi Etienne, if you already use betamfbc=2 then keep using that, it gives good results for the interhemispheric gradients, I thought you were using 1 and so I suggested 1.5 to introduce a softer change. We did some testing with 1.5 for CO2 in CY48R1 and it also looked good, if you have time and computing capacity you can test it yourself but if not there is no need to change it. The larger values act more on features such as plumes, if you are interested in these. There is no perfect value, with 1.5 plumes maybe represented slightly better (less weakened by the Mfixer) but the difference is not great. We currently do work on that and something better may come in time ..

[Previous page](https://forum.ecmwf.int/t/recommendations-for-mass-fixers-in-openifs/12164.md?page=1)