<p>The difference between advection and convection in Chemistry Transport models (CTMs) is a question of scale:</p>

<ul>
<li><strong>Advection</strong> is driven by winds that are provided by the meteorological input dataset. Thus, the wind is resolved in the meteorological data.</li>
<li><strong>Convection</strong> is driven by sub grid processes (e.g. temperature gradients) and is paramterized in CTMs.</li>
</ul>

<p>See for example:</p>

<ul>
<li>Pleim, 2007a. doi: <a href="http://dx.doi.org/10.1175/JAM2539.1">10.1175/JAM2539.1</a></li>
<li>Pleim, 2007b. doi: <a href="http://dx.doi.org/10.1175/JAM2534.1">10.1175/JAM2534.1</a></li>
<li>Rasch et al., 1997. doi: <a href="http://dx.doi.org/10.1029/97JD02087">10.1029/97JD02087</a></li>
</ul>

CC BY-SA 3.0
2016-03-29T09:08:42.697Z
2016-03-29T09:08:42.697Z
daniel.heydebreck
<p>In atmospheric, the change of mixing ration $C_i$ of a chemical species $i$ is determined by:         </p>

<p>$\frac{\partial C_i }{\partial t} = -\bigtriangledown (VC_i)+\frac{\partial  }{\partial z}(k_z\frac{\partial C_i }{\partial z}) + (\frac{\partial C_i }{\partial z})_{dry}++ (\frac{\partial C_i }{\partial z})_{wet}+(\frac{\partial C_i }{\partial z})_{conv}+P_i-L_i+E_i$</p>

<ol>
<li>The first term represent the $Ci$ change due to horizontal and vertical advection.         </li>
<li>The fifith term on the right hand represent the $Ci$ due to the vertical convection.   </li>
</ol>

<p>I have read about this question <a href="https://physics.stackexchange.com/questions/24489/what-exactly-is-the-difference-between-advection-and-convection/118738#comment539944_118738">"What exactly is the difference between advection and convection?"</a>.        </p>

<p>The answer told, which I quoted:   </p>

<blockquote>
  <p>Advection is the movement of some material dissolved or suspended in the  fluid.<br>
  Convection is the movement of a fluid, typically in response to heat.</p>
</blockquote>

<p>But when we are just talking about the chemical species. They are not in fluid form. So,how dos the convection process mean?       </p>

<p>Update:  The equation was from a phD dissertatio <em>Climate and Air Pollution Modeling in South America focus on Megacities</em>. Links <a href="https://www.mpimet.mpg.de/fileadmin/publikationen/Reports/WEB_BzE_76.pdf" rel="nofollow noreferrer">here</a>       </p>

CC BY-SA 3.0
2016-03-29T08:33:32.057Z
Conv = Convective Precipitation? Wet could only mean non-convective precipitation.
daniel.heydebreck
CC BY-SA 3.0
2016-03-29T08:44:03.827Z
Could you give a reference to the equation?
daniel.heydebreck
CC BY-SA 3.0
2016-03-30T23:06:39.420Z
why aren't the chemical species in fluid form?  aren't they subject to the same movement?
f.thorpe
CC BY-SA 3.0
2016-03-31T05:21:03.817Z
@farrenthorpe. In my opinion, chemical in particular phase were also included.
Han Zhengzu
<meteorology><atmosphere><atmospheric-chemistry><air-quality>
The difference of vertical advection and convection process for chemistry species
Han Zhengzu
# The difference of vertical advection and convection process for chemistry species

(Asked by: username_0 on 2016-03-29)

In atmospheric, the change of mixing ration $C\_i$ of a chemical species $i$ is determined by:

$\frac{\partial C\_i }{\partial t} = -\bigtriangledown (VC\_i)+\frac{\partial }{\partial z}(k\_z\frac{\partial C\_i }{\partial z}) + (\frac{\partial C\_i }{\partial z})\_{dry}++ (\frac{\partial C\_i }{\partial z})\_{wet}+(\frac{\partial C\_i }{\partial z})\_{conv}+P\_i-L\_i+E\_i$

1. The first term represent the $Ci$ change due to horizontal and vertical advection.
2. The fifith term on the right hand represent the $Ci$ due to the vertical convection.

I have read about this question ["What exactly is the difference between advection and convection?"](https://physics.stackexchange.com/questions/24489/what-exactly-is-the-difference-between-advection-and-convection/118738#comment539944_118738).

The answer told, which I quoted:

> Advection is the movement of some material dissolved or suspended in the fluid.  
> Convection is the movement of a fluid, typically in response to heat.

But when we are just talking about the chemical species. They are not in fluid form. So,how dos the convection process mean?

Update: The equation was from a phD dissertatio *Climate and Air Pollution Modeling in South America focus on Megacities*. Links [here](https://www.mpimet.mpg.de/fileadmin/publikationen/Reports/WEB_BzE_76.pdf)

**Tags:** meteorology, atmosphere, atmospheric-chemistry, air-quality

> **Comments:**
> **username_1**: Conv = Convective Precipitation? Wet could only mean non-convective precipitation.  
> **username_1**: Could you give a reference to the equation?  
> **username_2**: why aren't the chemical species in fluid form?  aren't they subject to the same movement?  
> **username_0**: @farrenthorpe. In my opinion, chemical in particular phase were also included.  

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## 1 answers

### Answer by username_1 on 2016-03-29. Score: 6 | Accepted answer

The difference between advection and convection in Chemistry Transport models (CTMs) is a question of scale:

* **Advection** is driven by winds that are provided by the meteorological input dataset. Thus, the wind is resolved in the meteorological data.
* **Convection** is driven by sub grid processes (e.g. temperature gradients) and is paramterized in CTMs.

See for example:

* Pleim, 2007a. doi: [10.1175/JAM2539.1](http://dx.doi.org/10.1175/JAM2539.1)
* Pleim, 2007b. doi: [10.1175/JAM2534.1](http://dx.doi.org/10.1175/JAM2534.1)
* Rasch et al., 1997. doi: [10.1029/97JD02087](http://dx.doi.org/10.1029/97JD02087)


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