# Mpasjedi: how to generate 4d simulated observations

**URL:** <https://forums.jcsda.org/t/mpasjedi-how-to-generate-4d-simulated-observations/373>\
**Category:** JEDI\
**Created:** [September 6, 2022, 3:21am UTC](https://forums.jcsda.org/t/mpasjedi-how-to-generate-4d-simulated-observations/373 "2022-09-06T03:21:34Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![LL\_GZ](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/ll_gz/32/107_2.png) [@LL\_GZ](https://forums.jcsda.org/u/LL_GZ)\
**Post date:** [September 6, 2022, 3:21am UTC](https://forums.jcsda.org/t/mpasjedi-how-to-generate-4d-simulated-observations/373/1 "2022-09-06T03:21:34Z")

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**I could be using mpasjedi\_hofx3d.x and hofx3d.yaml to generate simulated observations in 3D. But how to generate four-dimensional simulated observations using background field files of multiple time? I didn’t find an executable file like mpasjedi\_hofx4d.x. Or can mpasjedi\_hofx3d.x also do simulated observations in four dimensions?**

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**Author:** ![byoung-joo](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/byoung-joo/32/126_2.png) [@byoung-joo](https://forums.jcsda.org/u/byoung-joo)\
**Post date:** [September 9, 2022, 3:12pm UTC](https://forums.jcsda.org/t/mpasjedi-how-to-generate-4d-simulated-observations/373/2 "2022-09-09T15:12:46Z")

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Hi @LL_GZ,

We don’t yet actively support 4D H(x).

> I didn’t find an executable file like mpasjedi\_hofx4d.x. Or can mpasjedi\_hofx3d.x also do simulated observations in four dimensions?

There does exist an executable for 4D H(x) under build/bin directory: `mpasjedi_hofx.x`

As shown in the corresponding ctest yaml file (`test/testinput/hofx.yaml`), this includes the model integration inside the application (see yaml key `model`). You might want to compare `test/testinput/hofx.yaml` and `test/testinput/hofx3d.yaml` to see the major differences on the configuration.

> But how to generate four-dimensional simulated observations using background field files of multiple time?

Currently, `mpasjedi_hofx.x` can not handle the background field files of multiple time. As noted above, the application directly includes the model integration and simulates the 4D H(x).

Thank you,  
BJ