Further modification of icloud=3 scheme (#149)

TYPE: enhancement

KEYWORDS: cloud fraction, sub-grid scale clouds, icloud=3

SOURCE: Greg Thompson, RAL

DESCRIPTION OF CHANGES:
Some tuning for grid spacing dependence of critical RH (used in Sundqvist equation) based on 2015 year-long simulations validated against USCRN surface incoming solar radiation. Tests were run at 10km spacing, also 10 &3.3km spacing by Pedro Jimenez and evaluated against observations by Mei Xu. Total liquid and ice water paths from fractional clouds plus explicit clouds (microphysics created) permitted to be slightly larger (1.5kg/m^2). Draft journal manuscript describing sub-grid scale (SGS) cloud parameterization is in progress.

LIST OF MODIFIED FILES:
modified: phys/module_radiation_driver.F

TESTS CONDUCTED: Regtested with WTF-3.06. RAL conducted 52 individual 36-h simulations for 2015, and obtained near-zero downward solar radiation bias over CONUS.

phys/module_radiation_driver.F

@@ -3164,7 +3164,7 @@ SUBROUTINE cal_cldfra3(CLDFRA, qv, qc, qi, qs,                    &
       REAL, DIMENSION(ims:ime,kms:kme,jms:jme):: qvsat
       INTEGER:: i,j,k
       REAL:: TK, TC, qvsi, qvsw, RHUM, xx, yy
-      REAL, DIMENSION(kms:kme):: qvs1d, cfr1d, T1d,                     &
+      REAL, DIMENSION(kts:kte):: qvs1d, cfr1d, T1d,                     &
      &                           P1d, R1d, qc1d, qi1d, qs1d
 
       character*512 dbg_msg
@@ -3178,8 +3178,8 @@ SUBROUTINE cal_cldfra3(CLDFRA, qv, qc, qi, qs,                    &
 !.. to get near 100% RH as grid spacing moves toward 1.0km, but higher
 !.. RH over ocean required as compared to over land.
 
-      RH_00L = 0.781 + SQRT(1./(35.0+gridkm*gridkm*gridkm*0.5))
-      RH_00O = 0.831 + SQRT(1./(70.0+gridkm*gridkm*gridkm*0.5))
+      RH_00L = 0.7  + SQRT(1./(25.0+gridkm*gridkm*gridkm))
+      RH_00O = 0.81 + SQRT(1./(50.0+gridkm*gridkm*gridkm))
 
       DO j = jts,jte
       DO k = kts,kte
@@ -3215,10 +3215,9 @@ SUBROUTINE cal_cldfra3(CLDFRA, qv, qc, qi, qs,                    &
             if (tc .ge. -12.0) then
                RHUM = MIN(0.999, RHUM)
                CLDFRA(I,K,J) = MAX(0.0, 1.0-SQRT((1.0-RHUM)/(1.-RH_00)))
-            elseif (tc.lt.-12..and.tc.gt.-70. .and. RHUM.gt.RH_00O) then
-               RHUM = MAX(0.01, MIN(qv(i,k,j)/qvsat(i,k,j), qvsw/qvsi - 1.E-6))
-               RHI_max = MAX(RHUM+1.E-6, qvsw/qvsi)
-               CLDFRA(I,K,J) = MAX(0., 1.0-SQRT((RHI_max-RHUM)/(RHI_max-RH_00O)))
+            elseif (tc.lt.-12..and.tc.gt.-70. .and. RHUM.gt.RH_00L) then
+               RHUM = MAX(0.01, MIN(qv(i,k,j)/qvsat(i,k,j), 1.0 - 1.E-6))
+               CLDFRA(I,K,J) = MAX(0., 1.0-SQRT((1.0-RHUM)/(1.0-RH_00L)))
             endif
             CLDFRA(I,K,J) = MIN(0.90, CLDFRA(I,K,J))
 
@@ -3302,8 +3301,8 @@ SUBROUTINE find_cloudLayers(qvs1d, cfr1d, T1d, P1d, R1d, entrmnt, &
       k_m40C = 0
       DO k = kte, kts, -1
          theta(k) = T1d(k)*((100000.0/P1d(k))**(287.05/1004.))
-         if (T1d(k)-273.16 .gt. -40.0) k_m40C = MAX(k_m40C, k)
-         if (T1d(k)-273.16 .gt. -12.0) k_m12C = MAX(k_m12C, k)
+         if (T1d(k)-273.16 .gt. -40.0 .and. P1d(k).gt.7000.0) k_m40C = MAX(k_m40C, k)
+         if (T1d(k)-273.16 .gt. -12.0 .and. P1d(k).gt.10000.0) k_m12C = MAX(k_m12C, k)
       ENDDO
       if (k_m40C .le. kts) k_m40C = kts
       if (k_m12C .le. kts) k_m12C = kts
@@ -3491,7 +3490,6 @@ SUBROUTINE adjust_cloudIce(cfr,qi,qs,qvs, T,Rho,dz, entr, k1,k2,kts,kte)
       do k = k1, k2
          iwp_exists = iwp_exists + (qi(k)+qs(k))*Rho(k)*dz(k)
       enddo
-      if (iwp_exists .gt. 1.0) RETURN
 
       this_dz = 0.0
       do k = k1, k2
@@ -3535,7 +3533,6 @@ SUBROUTINE adjust_cloudH2O(cfr, qc, qvs, T,Rho,dz, entr, k1,k2,kts,kte)
       do k = k1, k2
          lwp_exists = lwp_exists + qc(k)*Rho(k)*dz(k)
       enddo
-      if (lwp_exists .gt. 1.0) RETURN
 
       this_dz = 0.0
       do k = k1, k2
@@ -3571,20 +3568,15 @@ SUBROUTINE adjust_cloudFinal(cfr, qc, qi, Rho,dz, kts,kte,k_tropo)
       INTEGER:: k
 
       lwp = 0.
-      do k = kts, k_tropo
-         if (cfr(k).gt.0.01 .and. cfr(k).lt.0.99) then
-            lwp = lwp + qc(k)*Rho(k)*dz(k)
-         endif
-      enddo
-
       iwp = 0.
       do k = kts, k_tropo
-         if (cfr(k).gt.0.01 .and. cfr(k).lt.0.99) then
+         if (cfr(k).gt.0.0) then
+            lwp = lwp + qc(k)*Rho(k)*dz(k)
             iwp = iwp + qi(k)*Rho(k)*dz(k)
          endif
       enddo
 
-      if (lwp .gt. 1.0) then
+      if (lwp .gt. 1.5) then
          xfac = 1./lwp
          do k = kts, k_tropo
             if (cfr(k).gt.0.01 .and. cfr(k).lt.0.99) then
@@ -3593,7 +3585,7 @@ SUBROUTINE adjust_cloudFinal(cfr, qc, qi, Rho,dz, kts,kte,k_tropo)
          enddo
       endif
 
-      if (iwp .gt. 1.0) then
+      if (iwp .gt. 1.5) then
          xfac = 1./iwp
          do k = kts, k_tropo
             if (cfr(k).gt.0.01 .and. cfr(k).lt.0.99) then