<blockquote>
<p>What Pa level should I use...</p>
</blockquote>
<p>That really depends what you're trying to do with it.</p>
<blockquote>
<p>Is this data just missing near the surface?</p>
</blockquote>
<p>The pressure level 1 <code>hur</code> data in your ACCESS model plot are missing because the surface pressure in those grid boxes is less than 962.5 hPa lower bound of that layer.  In other words, that atmospheric layer doesn't exist above those grid boxes, so properties of it like temperature and humidity are not defined.  If you look at pressure levels 2, 3, etc, you should notice less and less of the area is undefined.</p>
<p>To be honest, looking at pressure level 1 isn't very useful for this reason.  In some places it'll be undefined, in some places it'll be inside the boundary layer and in some places it'll be outside, making interpretation difficult.</p>
<p>If you're looking at a single level this close to the surface, then you probably really want to look at the screen-level humidity variable, <code>hurs</code>.  That will be defined everywhere, is more comparable between models and is usually more relevant when looking at surface level impacts and applications.  The same is true for temperature variables <code>ta</code> and <code>tas</code>.</p>

CC BY-SA 4.0
2021-10-05T12:31:38.900Z
2021-10-05T12:31:38.900Z
Deditos
<p>I have downloaded a number of future simulations for a group of GCMs from CMIP6 for the variable Relative Humidity (hur).
I chose the 100000pa level to view the RH data in panoply for the EC-Earth iteration and it looked normal/as expected:
<a href="https://i.sstatic.net/wjvuP.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/wjvuP.png" alt="enter image description here" /></a></p>
<p>However, when I checked the other models at (or near to) this Pa level, most of the RH data was missing from the landmasses:
<a href="https://i.sstatic.net/7CmbM.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/7CmbM.png" alt="enter image description here" /></a></p>
<p>Am I using the wrong Pa level? Is this data just missing near the surface?</p>
<p>Any advice appreciated.</p>

<climate-models><humidity>
What Pa level should I use when looking at Relative Humidity data from CMIP6 models?
matlabcat
# What Pa level should I use when looking at Relative Humidity data from CMIP6 models?

(Asked by: username_0 on 2021-10-05)

I have downloaded a number of future simulations for a group of GCMs from CMIP6 for the variable Relative Humidity (hur).
I chose the 100000pa level to view the RH data in panoply for the EC-Earth iteration and it looked normal/as expected:
[![enter image description here](https://i.sstatic.net/wjvuP.png)](https://i.sstatic.net/wjvuP.png)

However, when I checked the other models at (or near to) this Pa level, most of the RH data was missing from the landmasses:
[![enter image description here](https://i.sstatic.net/7CmbM.png)](https://i.sstatic.net/7CmbM.png)

Am I using the wrong Pa level? Is this data just missing near the surface?

Any advice appreciated.

**Tags:** climate-models, humidity


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## 1 answers

### Answer by username_1 on 2021-10-05. Score: 4 | Accepted answer

> What Pa level should I use...

That really depends what you're trying to do with it.

> Is this data just missing near the surface?

The pressure level 1 `hur` data in your ACCESS model plot are missing because the surface pressure in those grid boxes is less than 962.5 hPa lower bound of that layer. In other words, that atmospheric layer doesn't exist above those grid boxes, so properties of it like temperature and humidity are not defined. If you look at pressure levels 2, 3, etc, you should notice less and less of the area is undefined.

To be honest, looking at pressure level 1 isn't very useful for this reason. In some places it'll be undefined, in some places it'll be inside the boundary layer and in some places it'll be outside, making interpretation difficult.

If you're looking at a single level this close to the surface, then you probably really want to look at the screen-level humidity variable, `hurs`. That will be defined everywhere, is more comparable between models and is usually more relevant when looking at surface level impacts and applications. The same is true for temperature variables `ta` and `tas`.


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