diff --git a/physics/GFS_rrtmgp_pre.F90 b/physics/GFS_rrtmgp_pre.F90
index a80c4b5a6..f75e251e7 100644
--- a/physics/GFS_rrtmgp_pre.F90
+++ b/physics/GFS_rrtmgp_pre.F90
@@ -251,7 +251,7 @@ subroutine GFS_rrtmgp_pre_run (Model, Grid, Statein, Coupling, Radtend, Sfcprop,
           relhum(iCol,iLay) = max( 0._kind_phys, min( 1._kind_phys, max(QMIN, q_lay(iCol,iLay))/qs ) )
           qs_lay(iCol,iLay) = qs
           tv_lay(iCol,iLay) = t_lay(iCol,iLay) * (1._kind_phys + fvirt*q_lay(iCol,iLay)) 
-          deltaZ(iCol,iLay) = (rog*0.001) * (log(p_lev(iCol,iLay)) - log(p_lev(iCol,iLay+1))) * tv_lay(iCol,iLay)
+          deltaZ(iCol,iLay) = (rog) * abs(log(p_lev(iCol,iLay)) - log(p_lev(iCol,iLay+1))) * tv_lay(iCol,iLay)
        enddo
     enddo