Hi Mario

At the beginning I need to say that I do not have the MATLAB code and I did not reproduce those parameter arrays successfully. But my experience may give you some information (which of course may be misleading).

The Gong function (and its modification by Gantt et al. (2015)) has two peaks, and CMAQ uses two lognormal distributions to fit it, one for fine mode particles (“J”) and one for coarse mode particles (“K”). Each lognormal distribution can be characterized by three parameters, that is, geometric mean (DGN), geometric standard deviation (SIG), and the amplitude (FN). Once the fitting is done, you get the three parameters. (Wind speed is 1 for the fitting.)

One fitting can only provide one value for each parameter. The 136 values in each array come from the RH-dependence of the Gong flux function, that is, there are many flux functions at different RH. Usually, only a flux function at RH=80% is provided, and you need to calculate the flux function at other RH. CMAQ calculates the functions from RH=45% to RH=99% based on the work of Zhang et al. (2005, 2006). From RH=45% to RH=90%, there is one flux function for each 1% RH, and from 90.1% to 99%, there is one flux function for each 0.1% RH. The total number of flux functions is therefore 90-45+1+(99-90.1)*10+1=136.

Because the Gong function seems not strictly a combination of two lognormal distributions, you may need to judge when the fitting is the best.

By the way, from the information you provide (THETA=8), it seems that you are using CMAQv5.2 or v5.3 where the SSA source function is not the Gong function but the modified version by Gantt et al. When I tried to compare these two source functions, I tried to calculate the parameters for the original Gong function myself, but finally I gave up and just copied those parameters from old version of CMAQ. But if you want to investigate the impact of THETA values or want to use other source functions, you have to calculate the parameters yourself.

Best Regards,

Zhizhua

References

Gantt, B., Kelly, J. T., and Bash, J. O.: Updating sea spray aerosol emissions in the Community Multiscale Air Quality (CMAQ) model version 5.0.2, Geoscientific Model Development, 8, 3733-3746, 10.5194/gmd-8-3733-2015, 2015.

Zhang, K. M., Knipping, E. M., Wexler, A. S., Bhave, P. V., and Tonnesen, G. S.: Size distribution of sea-salt emissions as a function of relative humidity, Atmospheric Environment, 39, 3373-3379, 10.1016/j.atmosenv.2005.02.032, 2005.

Zhang, K. M., Knipping, E. M., Wexler, A. S., Bhave, P. V., and Tonnesen, G. S.: Reply to comment on “Size distribution of sea-salt emissions as a function of relative humidity”, Atmospheric Environment, 40, 591-592, 10.1016/j.atmosenv.2005.08.044, 2006.