Mexico surrogates are the same as these:
/work/EMIS/em_v7.2/ge_dat/gridding/surrogates/CONUS12_2015CAN_2010MEX_03dec2018/
except with column and row numbers shifted to the 516x444 domain that the Canada
surrogates use. Col/row shifting performed here: /work/EMIS/users/cvy/sas/WO270.3/surrogates/
