I am not familiar with the met2mgn.v210.csh script, but the error message above is clear enough: METCRO2Dfile1 is defined properly in your run script and is openend, but METCRO2Dfile2 is not defined and therefore cannot be opened.
The relevant section of your run script from your first post shows this:
if ($JDATE == $EPISODE_SDATE) then
setenv METCRO2Dfile1 $INPPATH/chengdu_1h/METCRO2D_case1_old.nc
else
setenv METCRO2Dfile1 $INPPATH/chengdu_1h/METCRO2D_case1_old.nc
setenv METCRO2Dfile2 $INPPATH/chengdu_1h/METCRO2D_case1_old.nc
endif
So, when JDATE equals EPISODE_SDATE, METCRO32Dfile2 isn’t defined which then causes met2mgn to crash. The solution would seem to be to always define both METCRO2Dfile1 and METCRO2Dfile2. That said, I don’t know what distinguishes these two files from met2mgn’s perspective and whether or not it is appropriate to set both variables to the same file as is done in the second section of the if ... then block.