# Zos : sea\_surface\_height\_above\_geoid in NEMO

**URL:** https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515
**Category:** v4.2.x
**Created:** [22 May 2023 11:26 UTC](https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515 "2023-05-22T11:26:24Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![amrtalaat](https://yyz2.discourse-cdn.com/free1/user_avatar/nemo-ocean.discourse.group/amrtalaat/32/102_2.png) [@amrtalaat](https://nemo-ocean.discourse.group/u/amrtalaat)
#### Post date: [22 May 2023 11:26 UTC](https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515/1 "2023-05-22T11:26:24Z")

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I have the variable **zos** being saved in a **grid\_T.nc** file. Based on the standard name, this variable represents the “sea surface height above geoid” which is the **Absolute Dynamic Topography (ADT)** :

Since,

**ADT = SLAp + MDTp**

Where:

SLAp : Sea level anomaly over period p.  
MDTp : Mean Dynamic Topography over period p

My question is: How can I get the **MDTp** values from the **NEMO** model ?

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### Author: ![robinson](https://avatars.discourse-cdn.com/v4/letter/r/848f3c/32.png) [@robinson](https://nemo-ocean.discourse.group/u/robinson)
#### Post date: [15 June 2023 14:55 UTC](https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515/2 "2023-06-15T14:55:36Z")

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Hei,

I do not have the answer to your question, but I know someone who might, Vahidreza Jahanmard, a PhD student in Taltech in Tallinn.

Hope this helps,

Robinson

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### Author: ![amrtalaat](https://yyz2.discourse-cdn.com/free1/user_avatar/nemo-ocean.discourse.group/amrtalaat/32/102_2.png) [@amrtalaat](https://nemo-ocean.discourse.group/u/amrtalaat)
#### Post date: [30 June 2023 11:06 UTC](https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515/3 "2023-06-30T11:06:16Z")

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Thanks Robinson, I will contact.

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### Author: ![Saeed](https://avatars.discourse-cdn.com/v4/letter/s/e8c25b/32.png) [@Saeed](https://nemo-ocean.discourse.group/u/Saeed)
#### Post date: [1 August 2023 10:41 UTC](https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515/4 "2023-08-01T10:41:16Z")

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Hi

one way of getting MDTP is to calculating long term averge of SSH fron nemo output. I do now not know how long is enough but the longer the better. If yoy have tides as part of your SSH, i guess it should cover the lowest astronomical tidal period which i think it is around 18 years.

Saeed

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### Author: ![Jeenu](https://avatars.discourse-cdn.com/v4/letter/j/43a26b/32.png) [@Jeenu](https://nemo-ocean.discourse.group/u/Jeenu)
#### Post date: [6 July 2024 16:57 UTC](https://nemo-ocean.discourse.group/t/zos-sea-surface-height-above-geoid-in-nemo/515/5 "2024-07-06T16:57:51Z")

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Hi amrtalaat,  
Did you able to find the answer?.Could you please help me to calculate the Mean Dynamic Topography over period p