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Grd_xlat2 = 0.,
Grd_xlon2 = Grd_xlon1 + 90. - => You need to set it to the value 'Grd_xlon1 + 90.', do not actually put 'Grd_xlon1' here!!!
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...
Grd_xlat2 = 0.,
Grd_xlon2 = Grd_xlon1 + 90. - => You need to set it to the value 'Grd_xlon1 + 90.', do not actually put 'Grd_xlon1' here!!!
...