Scheduled Downtime
On Friday 21 April 2023 @ 5pm MT, this website will be down for maintenance and expected to return online the morning of 24 April 2023 at the latest

Output AOD all zeros

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.


New member
Dear colleagues,

I am running WRF-chem with the aerosol settings of aer_opt = 1 and aer_op_opt = 2.
However, all the output variables related to AOD contain all zeros.

Would you please give me a hint about what could go wrong?
Here is my namelist: View attachment namelist.input.

Thank you very much & Happy Holidays!
Consulted Dr. Jordan Schnell from CIRES.

AOD contains all zeros because in "WRF v4.2, AOD_OUT and AOD2D_OUT are not actually hooked up correctly - they are only initialized in phys/module_radiation driver.F."

Instead, we can output the extinction coefficient as follows:

"Set opt_pars_out = 1 in the chem namelist. That should then output 3D extinction coefficients at 3 different wavelengths (300, 550, and 1060 nm), which you can integrate vertically to get AOD. Take a look at Registry/registry.chem, this line tells you what variables are activated (and memory allocated for) with the opt_pars_out namelist option:

package opt_out opt_pars_out==1 - ext_coef:extcof3,extcof55,extcof106,extcof3_5,extcof8_12;bscat_coef:bscof3,bscof55,bscof106;asym_par:asympar3,asympar55,asympar106

i.e., also scattering coefficients and asymmetry parameters

Then you will also probably need to either change the Registry (and then ./clean -a, recompile) or add an iofields file to your run directory (and namelist) to add the variable(s) you want to the history channel. For example, the extinction coefficient at 550 nm should be output because it has an “h” (history):

state real extcof55 ikjf ext_coef 1 Z h "EXTCOF55" "Extinction coefficients for .55um" "km^-1”

Dear woodllan ,

Acc to your answer, how to now calculate the AOD from the ext coefficient variables?

Please help.

Hi Lin,

To calculate AOD, you just need to integrate the extinction coef throughout the entire model column; i.e. multiple the extinction coef by the thickness of the model box and sum all the boxes:

AOD = ∑ EXT(l) * dz(l)