diff --git a/phys/module_fr_fire_util.F b/phys/module_fr_fire_util.F
index 28f07bb833..8558990229 100644
--- a/phys/module_fr_fire_util.F
+++ b/phys/module_fr_fire_util.F
@@ -68,7 +68,7 @@ subroutine interpolate_z2fire(id,                 & ! for debug output, <= 0 no
     zsf,flag_z0)                                      ! fire grid arrays out
     
 implicit none
-!*** purpose: interpolate height
+!*** purpose: interpolate height or any other 2d variable defined at mesh cell centers
 
 !*** arguments
 integer, intent(in)::id,                          &