<p>Your method looks OK, however, <a href="https://water.usgs.gov/edu/density.html" rel="nofollow noreferrer">water density varies with temperature</a>.</p>

<p>Not knowing exactly what your aim is or how accurate/fussy you want to be, you may want to consider using the density of water for its temperature rather than accepted average of $1000 kg/m^3$.</p>

CC BY-SA 3.0
2017-01-10T10:11:35.000Z
Well, I need it as an input into another model ([MEGAN](http://www.lar.wsu.edu/megan/guides.html) - not sure if anyone is familiar with it but that's not so important). The trouble is I have so far no idea how sensitive the model is to these parameters. I just wasn't sure if the properties of water contained in soil would be the same as those of any "other" water.
Janina
CC BY-SA 3.0
2017-01-10T01:37:58.967Z
2017-01-10T01:37:58.967Z
Fred
<p>I am using the outputs of the <a href="http://www.weather.bg/0index.php?koiFail=txt/textAladin&amp;lng=1" rel="nofollow noreferrer">ALADIN meteorological model</a>, in particular I need volumetric soil moisture. However, the output from ALADIN is in "funny" units - $\mathrm{kg/m}^2$ per top 1 cm. Is it acceptable to assume water density $\rho_w = 1000~\mathrm{kg/m}^3$ and calculate as follows:
$\frac{\mathrm{kg}}{\mathrm{m}^2.\mathrm{cm}}*\frac{100}{1000} = \frac{\mathrm{m}^3}{\mathrm{m}^3}$? So basically just take the values and divide them by 10? I don't need to be extra scientific, but I don't want to miss anything crucial.</p>

CC BY-SA 3.0
2017-01-10T23:08:21.347Z
If you are worried about solutes or temperature changing the water density, you may have to look into the underlying methods in the ALADIN model - it may assume pure water. I suspect the density correction wouldn't be significant relative to the model uncertainty. The other issue is how you are going to use the water content. It may not be appropriate to use the value for the top 1 cm - that gives you a boundary content but probably does not represent the mass present in a greater soil thickness.
haresfur
CC BY-SA 3.0
2017-01-11T08:28:39.127Z
@haresfur Thank you for your insight. As I commented on the answer below, I will be using the data as input for the MEGAN model (biogenic emissions). The documentation isn't too thorough, so I have to make assumptions - for example the variable description from the sample input data "volumetric soil moisture in top cm" suggests that the value for the top 1 cm should be just what I want.
Janina
<soil-moisture>
How to convert soil moisture units from meteorological model?
Janina
# How to convert soil moisture units from meteorological model?

(Asked by: username_0 on 2017-01-09)

I am using the outputs of the [ALADIN meteorological model](http://www.weather.bg/0index.php?koiFail=txt/textAladin&lng=1), in particular I need volumetric soil moisture. However, the output from ALADIN is in "funny" units - $\mathrm{kg/m}^2$ per top 1 cm. Is it acceptable to assume water density $\rho\_w = 1000~\mathrm{kg/m}^3$ and calculate as follows:
$\frac{\mathrm{kg}}{\mathrm{m}^2.\mathrm{cm}}\*\frac{100}{1000} = \frac{\mathrm{m}^3}{\mathrm{m}^3}$? So basically just take the values and divide them by 10? I don't need to be extra scientific, but I don't want to miss anything crucial.

**Tags:** soil-moisture

> **Comments:**
> **username_1**: If you are worried about solutes or temperature changing the water density, you may have to look into the underlying methods in the ALADIN model - it may assume pure water. I suspect the density correction wouldn't be significant relative to the model uncertainty. The other issue is how you are going to use the water content. It may not be appropriate to use the value for the top 1 cm - that gives you a boundary content but probably does not represent the mass present in a greater soil thickness.  
> **username_0**: @username_1 Thank you for your insight. As I commented on the answer below, I will be using the data as input for the MEGAN model (biogenic emissions). The documentation isn't too thorough, so I have to make assumptions - for example the variable description from the sample input data "volumetric soil moisture in top cm" suggests that the value for the top 1 cm should be just what I want.  

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## 1 answers

### Answer by username_2 on 2017-01-10. Score: 2 | Accepted answer

Your method looks OK, however, [water density varies with temperature](https://water.usgs.gov/edu/density.html).

Not knowing exactly what your aim is or how accurate/fussy you want to be, you may want to consider using the density of water for its temperature rather than accepted average of $1000 kg/m^3$.

> **Comments:**
> **username_0**: Well, I need it as an input into another model ([MEGAN](http://www.lar.wsu.edu/megan/guides.html) - not sure if anyone is familiar with it but that's not so important). The trouble is I have so far no idea how sensitive the model is to these parameters. I just wasn't sure if the properties of water contained in soil would be the same as those of any "other" water.  

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