Unify CONST1 and VISRH in GSD visibility calculation. (NOAA-EMC#318)

sorc/ncep_post.fd/CALVIS_GSD.f

@@ -87,6 +87,7 @@ SUBROUTINE CALVIS_GSD(CZEN,VIS)
 !   2015-17        S. Benjamin, T. Smirnova - modifications for RH-based clear-air vis
 !   2017-12        R. Ahmadov, Steve Albers - addition for attenuation from aerosols
 !                              (not related to water vapor or RH at this point)
+!   2021-05        Wen Meng        Unify CONST1 and VISRH. 
 !                           
 !------------------------------------------------------------------
 !
@@ -177,11 +178,7 @@ SUBROUTINE CALVIS_GSD(CZEN,VIS)
 
       EXPONFg    =   0.75  
 !     CONST1=-LOG(.02)
-      if(MODELNAME == 'RAPR') then
-         CONST1= 3.000
-      else
-         CONST1= 3.912
-      endif
+      CONST1= 3.000
 
 ! visibility with respect to RH is
 !   calculated from optical depth linearly
@@ -239,11 +236,7 @@ SUBROUTINE CALVIS_GSD(CZEN,VIS)
 
 !tgs 23 feb 2017 - increase of base value to 90 km to reduce attenuation
 !                  from RH for clear-air visibility.  (i.e., increase clear-air vis overall)
-       IF(MODELNAME  == 'RAPR') then
-          visrh = 90. * exp(-2.5*qrh)
-       else
-          visrh = 60. * exp(-2.5*qrh)
-       endif
+       visrh = 90. * exp(-2.5*qrh)
 
 !  -- add term to increase RH vis term for
 !     low-level wind shear increasing from 4 to 6 ms-1