Hello, everyone. I have read one paper which used CMAQ generate a curve line like this

I want to get the similar plots from CMAQ output. However I can only find concentration in 3 modes. How can I get the distribution for different particle diameters.

Hello,

The general approach is to chop up the range of particle size you are interested in (in the plot above the entire range is 0.01 to 0.5 um) into a relevant number of individual bins. Then for each size bin, you should calculate the number of particles between the lower and upper particle sizes for that bin. You will do this for each particle mode from CMAQ and sum them together.

The formula for calculating particle number is that of a log-normal distribution. See, for example, Binkowski and Roselle (2003), Eq. 1. If you are using a standard programming language like Python with the scipy library to calculate the pdf of the size distribution for each mode given mode-specific parameters and the bin range.

You will need the variables Dg (e.g. DGACC_DRY or DGACC_WET for the CMAQ accumulation mode dry or wet diameter, respectively) and standard deviation (STDEV_ACC for the CMAQ accumulation mode). You will also need to multiply by the total number concentration of particles in that mode (NUMACC for accumulation mode number).

Feel free to reach out with more questions.

Best wishes,

Ben Murphy

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Thanks for your reply. As I lack the background of related knowledge, it takes me some time to understand the paper. I will tell you, if I successfully get the result.