Scheduled Downtime
On Tuesday 24 October 2023 @ 5pm MT the forums will be in read only mode in preparation for the downtime. On Wednesday 25 October 2023 @ 5am MT, this website will be down for maintenance and expected to return online later in the morning.
Normal Operations
The forums are back online with normal operations. If you notice any issues or errors related to the forums, please reach out to help@ucar.edu

How to convert emissions (molecules/cm2/s) to mass emission (kg/m2/s)?

Francesca Bruno

ranqi
New Member
Hello, I have the input data for B2000CAM5CN (e.g. ar5_mam3_oc_surf_2000_c090726.nc). The unit for OC emission is molecules/cm2/s. I want to compare the emissions from EDAGR (emission unit is [kg/m2/s]) and that from CESM input data. So, how can I convert [molecules/cm2/s] to [kg/m2/s]? I think the calculation needs the molecular weight (MW), and I know that MW of SO2 is 64. But what is the WM for BC, OC and SOAG?
I'm stuck with this issue, I really appreciate any help!
 

nusbaume

Jesse Nusbaumer
CSEG and Liaisons
Staff member
Hi Ranqi,

I am moving this thread to the CAM-Chem forum, so that experts in CAM's chemistry routines can provide the information you need, at least with regards to the molecular weights.

Hope that helps, and have a great day!

Jesse
 

Francesca Bruno

ranqi
New Member
Hi Ranqi,

I am moving this thread to the CAM-Chem forum, so that experts in CAM's chemistry routines can provide the information you need, at least with regards to the molecular weights.

Hope that helps, and have a great day!

Jesse
Thank you, Jesse. It's so nice of you.
 

rrbuchholz

Rebecca Buchholz
CSEG and Liaisons
Staff member
Hi Ranqi,

Users can find the chemical formula used for each compound in ./CaseDocs/chem_mech.in or chem_mech.doc
We have added a file of molecular weights used in CAM-chem to the CAM-chem Wiki: https://wiki.ucar.edu/display/camchem/Using+CAM-chem+Output
The direct link to that file is here:
https://wiki.ucar.edu/download/attachments/372834728/species_molwts_2021-05-07.csv

The process of converting units:
  • There are 6.022e23 (Avogadro's number, N_Av) molecules in one mole of a particular species, so divide by N_Av to calculate the number of moles.
  • The MW of a species defines the number of grams per mole, so multiply my the MW.
  • To convert grams to kilograms, divide by 1000.
  • One meter squared is 100 cm x 100 cm so converting cm^2 to m^2, multiply by 10000.
In an equation:

Emissions (kg/m2/s) = y (molecules/cm^2/s) ÷ N_Av (molecules/mol) × MW (g/mol) ÷ 1000 (g/kg) × 10000 (cm^2/m^2)

Note that we are developing a python tool to also help with this:
Python Resources for CAM-chem

Hope that helps!
Best,
Rebecca
 

Francesca Bruno

ranqi
New Member
Hi Ranqi,

Users can find the chemical formula used for each compound in ./CaseDocs/chem_mech.in or chem_mech.doc
We have added a file of molecular weights used in CAM-chem to the CAM-chem Wiki: https://wiki.ucar.edu/display/camchem/Using+CAM-chem+Output
The direct link to that file is here:
https://wiki.ucar.edu/download/attachments/372834728/species_molwts_2021-05-07.csv

The process of converting units:
  • There are 6.022e23 (Avogadro's number, N_Av) molecules in one mole of a particular species, so divide by N_Av to calculate the number of moles.
  • The MW of a species defines the number of grams per mole, so multiply my the MW.
  • To convert grams to kilograms, divide by 1000.
  • One meter squared is 100 cm x 100 cm so converting cm^2 to m^2, multiply by 10000.
In an equation:

Emissions (kg/m2/s) = y (molecules/cm^2/s) ÷ N_Av (molecules/mol) × MW (g/mol) ÷ 1000 (g/kg) × 10000 (cm^2/m^2)

Note that we are developing a python tool to also help with this:
Python Resources for CAM-chem

Hope that helps!
Best,
Rebecca
Thank you so much, Rebecca. Your reply is very helpful and detailed. Now I know how to do the unit conversion!
 
Top