# MERRA2 aerosol

**URL:** <https://forums.jcsda.org/t/merra2-aerosol/620>\
**Category:** CRTM\
**Created:** [September 9, 2024, 8:54pm UTC](https://forums.jcsda.org/t/merra2-aerosol/620 "2024-09-09T20:54:30Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![sjlee](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@sjlee](https://forums.jcsda.org/u/sjlee)\
**Post date:** [September 9, 2024, 8:54pm UTC](https://forums.jcsda.org/t/merra2-aerosol/620/1 "2024-09-09T20:54:30Z")

</div>

I try to run the pyCRTM using MERRA2 aerosol data.  
MERRA2 3d data has 5 types of dust and 5 types of sea salt.  
In pyCRTM, based on the test sample, just 1 aerosol data is used here.

profiles.aerosols[i,:,0,0] = np.asarray(h5[‘aerosolConcentration’])  
profiles.aerosols[i,:,0,1] = np.asarray(h5[‘aerosolEffectiveRadius’])

How can I select one value of these data?  
And also, how can I calculate the aerosol effective radius?  
Or can you recommend some aerosol data for CRTM?

---

<div class="post-metadata">

**Author:** ![sjlee](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@sjlee](https://forums.jcsda.org/u/sjlee)\
**Post date:** [September 11, 2024, 1:13pm UTC](https://forums.jcsda.org/t/merra2-aerosol/620/2 "2024-09-11T13:13:45Z")

</div>

I found a way to change the number of input aerosols.  
Now I’m wondering how I can combine the 5 dust bins into one dust variable.

---

<div class="post-metadata">

**Author:** ![chengdang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/chengdang/32/185_2.png) [@chengdang](https://forums.jcsda.org/u/chengdang)\
**Post date:** [September 11, 2024, 6:13pm UTC](https://forums.jcsda.org/t/merra2-aerosol/620/3 "2024-09-11T18:13:03Z")

</div>

Hello, thanks for reaching out!  
You don’t need to combine the 5 dust bins. You may use 5 dust species, and assign the mode/average radii of the bins to the corresponding 5 dust species. With the default setup, CRTM will adjust the optical properties of dust based on input dust effective radius.

---

<div class="post-metadata">

**Author:** ![sjlee](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@sjlee](https://forums.jcsda.org/u/sjlee)\
**Post date:** [September 11, 2024, 6:47pm UTC](https://forums.jcsda.org/t/merra2-aerosol/620/4 "2024-09-11T18:47:48Z")

</div>

Thanks for answering! 😃

The term “assign mode” refers to specifying the aerosol type, is it correct?  
I was planning to input the aerosol concentrations and use the effective radius values (Reff) from the “AerosolCoeff.nc4” file to run CRTM.

If I want to use 5 dust bins, do I have to manually calculate the effective radius of each layer and put it as a variable?

---

<div class="post-metadata">

**Author:** ![chengdang](https://yyz1.discourse-cdn.com/flex031/user_avatar/forums.jcsda.org/chengdang/32/185_2.png) [@chengdang](https://forums.jcsda.org/u/chengdang)\
**Post date:** [October 2, 2024, 5:01pm UTC](https://forums.jcsda.org/t/merra2-aerosol/620/5 "2024-10-02T17:01:41Z")

</div>

Hello

> The term “assign mode” refers to specifying the aerosol type, is it correct?

Yes. With the default table “AerosolCoeff.nc4” file, you need to specify the aerosol type, and you also need to input/assign the profiles of effective radius.

> If I want to use 5 dust bins, do I have to manually calculate the effective radius of each layer and put it as a variable?

Yes, that would be the case. You may use the effective radius of MERRA2 aerosols as input for CRTM.