# Perturbing the initial state for ensemble runs **URL:** \ **Category:** OpenIFS\ **Tags:** openifs-configuration-and-namelists, openifs-initial-data, openifs-43r3\ **Created:** [9 May 2023 19:50 UTC](https://forum.ecmwf.int/t/perturbing-the-initial-state-for-ensemble-runs/12110 "2023-05-09T19:50:28Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Abhishek\_Savita](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/a/a698b9/32.png) [@Abhishek\_Savita](https://forum.ecmwf.int/u/Abhishek_Savita)\ **Post date:** [9 May 2023 19:50 UTC](https://forum.ecmwf.int/t/perturbing-the-initial-state-for-ensemble-runs/12110/1 "2023-05-09T19:50:28Z")
``` perturb: 1 ensemble_id: 1 ``` ---
**Author:** ![Marcus\_Koehler](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/marcus_koehler/32/1000_2.png) [@Marcus\_Koehler](https://forum.ecmwf.int/u/Marcus_Koehler)\ **Post date:** [10 May 2023 08:22 UTC](https://forum.ecmwf.int/t/perturbing-the-initial-state-for-ensemble-runs/12110/2 "2023-05-10T08:22:55Z")
Dear Abhishek Savita, Can you provide a bit more information and context about what you are doing with OpenIFS and what problems you are experiencing?  Otherwise it will be difficult for anyone in the user community to make any suggestions to help you.  Thank you! Marcus ---
**Author:** ![Abhishek\_Savita](https://forum.ecmwf.int/letter_avatar_proxy/v4/letter/a/a698b9/32.png) [@Abhishek\_Savita](https://forum.ecmwf.int/u/Abhishek_Savita)\ **Post date:** [10 May 2023 08:36 UTC](https://forum.ecmwf.int/t/perturbing-the-initial-state-for-ensemble-runs/12110/3 "2023-05-10T08:36:25Z")
Thanks Marcus Koehler, Actually I was running few ensemble member runs using OpenIFS model, and for the ensemble run 4 (i.e., `ensemble_id: 4) by mistake I set ``perturb: 2. I was wondering if we set perturb: 2 then the initial state will pertubed or not. However, I did a test run in which I set perturb: 2 and perturb: 3 and found that they are similar. Which suggest that if we want to perturbed the initial state we only set perturb: 1 other numbers does not work. I also check with @Jokaim and he suggested to look at ESM-tools` "You can check this in ESM-Tools. `configs/components/oifs/oifs.yaml` shows that the `perturb` variable gets passed as an argument to the script `configs/components/oifs/oifs-43r3-preprocess.sh`. This shell script says: Bash 1 2 `# Modify SKT (skin-temp) field to create ensemble members if [["x${perturb}" == "x1"]] ; then` So if `perturb=1` then we add perturbations. If it is anything else, we don't do any perturbations. " So, the question I had is solved now. Abhi: ` ` ---
**Author:** ![Marcus\_Koehler](https://forum.ecmwf.int/user_avatar/forum.ecmwf.int/marcus_koehler/32/1000_2.png) [@Marcus\_Koehler](https://forum.ecmwf.int/u/Marcus_Koehler)\ **Post date:** [10 May 2023 09:11 UTC](https://forum.ecmwf.int/t/perturbing-the-initial-state-for-ensemble-runs/12110/4 "2023-05-10T09:11:08Z")
Hi Abhishek, OK, glad that you could find a solution to your question.  Ensembles is not something that we routinely support from the OpenIFS side here at ECMWF, or at least not at this time.  If your question is specific to use of OpenIFS within an EC-Earth context please do mention this in your original post for clarity.  This forum is read by all OpenIFS users and many (or most users) are actually not working with EC-Earth.  I believe EC-Earth have their own user forums where you are likely to find help for questions that relate to the model in EC-Earth configuration.  But I don't want to discourage you from posting here! ![(wink)](https://confluence.ecmwf.int/s/-ol1tgb/9012/1962nzv/_/images/icons/emoticons/wink.svg) Best regards, Marcus