The BC/IC generation tool for CMAQ that I use for CMAQ also creates these six modal number and surface area density variables, also listed in CMAQ species list - but I am not sure if CMAQ benefits from these variables for its BCs or ICs:
float NUMATKN(TSTEP, LAY, PERIM) ;
NUMATKN:long_name = "NUMATKN " ;
NUMATKN:units = "#/m**3 " ;
NUMATKN:var_desc = "VARIABLE NUMATKN ";
float NUMACC(TSTEP, LAY, PERIM) ;
NUMACC:long_name = "NUMACC " ;
NUMACC:units = "#/m**3 " ;
NUMACC:var_desc = "VARIABLE NUMACC " ;
float NUMCOR(TSTEP, LAY, PERIM) ;
NUMCOR:long_name = "NUMCOR " ;
NUMCOR:units = "#/m**3 " ;
NUMCOR:var_desc = "VARIABLE NUMCOR " ;
float SRFATKN(TSTEP, LAY, PERIM) ;
SRFATKN:long_name = "SRFATKN " ;
SRFATKN:units = "m**2/m**3 " ;
SRFATKN:var_desc = "VARIABLE SRFATKN " ;
float SRFACC(TSTEP, LAY, PERIM) ;
SRFACC:long_name = "SRFACC " ;
SRFACC:units = "m**2/m**3 " ;
SRFACC:var_desc = "VARIABLE SRFACC " ;
float SRFCOR(TSTEP, LAY, PERIM) ;
SRFCOR:long_name = "SRFCOR " ;
SRFCOR:units = "m**2/m**3 " ;
SRFCOR:var_desc = "VARIABLE SRFCOR " ;