<p>Use (1) Precipitation, as it is the sum of convective and non-convective precipitation, integrate it over one day, voilà.</p>

<p>converting [$kg/(m^2 s)$] (precip):
$$ precip [kg/(m^2 s)] \cdot dt [s] \cdot \frac{1}{ \rho_w [kg/(m^3)]} \cdot 1000 [mm/m] = total\_precip [mm]$$</p>

<p>where $\rho_w$ is the density of water.</p>

<p>Practically the last two factors cancel.</p>

CC BY-SA 3.0
2016-03-26T11:09:44.080Z
Thanks for your reply. I have known the meaning of sum RAINS & RAINNS. But you answer let me know why the units change to $mm$. That's very helpful!
Han Zhengzu
CC BY-SA 3.0
2016-03-26T11:01:46.433Z
2016-03-26T11:01:46.433Z
Lukas
<p>From WRF output file,     </p>

<p>I find 3 variables related to the precipitation (unit: mm)</p>

<p><strong>1. Precipitation</strong>    </p>

<ul>
<li>variable name: pr     </li>
<li>unit:$kg/(m^{2}s^1)$     </li>
<li>variable: RAINC+RAINNC     </li>
<li>comments: $dt(RAINC+RAINNC)/DT$</li>
</ul>

<p><strong>2. Max hourly precipitation rate</strong>    </p>

<ul>
<li>variable name: prhmax     </li>
<li>unit:$kg/(m^{2}s^1)$     </li>
<li>variable: RAINC, RAINNC or RAINMAX1Hclwrf   </li>
<li>comments: $MAX(dtsum()/DT)$</li>
</ul>

<p><strong>3. Convective precipitation</strong>    </p>

<ul>
<li>variable name: prc     </li>
<li>unit:$kg/(m^{2}s^1)$     </li>
<li>variable: RAINC </li>
<li>comments: $d_t(RAINC)/DT $       </li>
</ul>

<p>My task:      </p>

<blockquote>
  <p>Summarize the amount of days which precipitation > 0.254 mm       </p>
</blockquote>

<p>What variable should I use for further analysis?   </p>

<p>Any advice would be appreciated. </p>

<meteorology><atmosphere><atmosphere-modelling><wrf>
Calculate precipitation from WRF model output
Han Zhengzu
# Calculate precipitation from WRF model output

(Asked by: username_0 on 2016-03-26)

From WRF output file,

I find 3 variables related to the precipitation (unit: mm)

**1. Precipitation**

* variable name: pr
* unit:$kg/(m^{2}s^1)$
* variable: RAINC+RAINNC
* comments: $dt(RAINC+RAINNC)/DT$

**2. Max hourly precipitation rate**

* variable name: prhmax
* unit:$kg/(m^{2}s^1)$
* variable: RAINC, RAINNC or RAINMAX1Hclwrf
* comments: $MAX(dtsum()/DT)$

**3. Convective precipitation**

* variable name: prc
* unit:$kg/(m^{2}s^1)$
* variable: RAINC
* comments: $d\_t(RAINC)/DT $

My task:

> Summarize the amount of days which precipitation > 0.254 mm

What variable should I use for further analysis?

Any advice would be appreciated.

**Tags:** meteorology, atmosphere, atmosphere-modelling, wrf


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## 1 answers

### Answer by username_1 on 2016-03-26. Score: 8 | Accepted answer

Use (1) Precipitation, as it is the sum of convective and non-convective precipitation, integrate it over one day, voilà.

converting [$kg/(m^2 s)$] (precip):
$$ precip [kg/(m^2 s)] \cdot dt [s] \cdot \frac{1}{ \rho\_w [kg/(m^3)]} \cdot 1000 [mm/m] = total\\_precip [mm]$$

where $\rho\_w$ is the density of water.

Practically the last two factors cancel.

> **Comments:**
> **username_0**: Thanks for your reply. I have known the meaning of sum RAINS & RAINNS. But you answer let me know why the units change to $mm$. That's very helpful!  

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