subroutine radar_simulator(freq,k2,do_ray,use_gas_abs,use_mie_table,mt, &
    nhclass,hp,nprof,ngate,nsizes,D,hgt_matrix,hm_matrix,re_matrix,p_matrix,t_matrix, &
    rh_matrix,Ze_non,Ze_ray,h_atten_to_vol,g_atten_to_vol,dBZe, &
    g_to_vol_in,g_to_vol_out)

!     rh_matrix,Ze_non,Ze_ray,kr_matrix,g_atten_to_vol,dBZe)
 
  use m_mrgrnk 
  use array_lib
  use math_lib
  use optics_lib
  use radar_simulator_types
  implicit none
  
! Purpose:
!   Simulates a vertical profile of radar reflectivity
!   Part of QuickBeam v1.04 by John Haynes & Roger Marchand
!
! Inputs:
!   [freq]            radar frequency (GHz), can be anything unless
!                     use_mie_table=1, in which case one of 94,35,13.8,9.6,3
!   [k2]              |K|^2, the dielectric constant, set to -1 to use the
!                     frequency dependent default
!   [do_ray]          1=do Rayleigh calcs, 0=not
!   [use_gas_abs]     1=do gaseous abs calcs, 0=not,
!                     2=use same as first profile (undocumented)
!   [use_mie_table]   1=use Mie tables, 0=not
!   [mt]              Mie look up table
!   [nhclass]         number of hydrometeor types
!   [hp]              structure that defines hydrometeor types
!   [nprof]           number of hydrometeor profiles
!   [ngate]           number of vertical layers
!   [nsizes]          number of discrete particles in [D]
!   [D]               array of discrete particles (um)
!
!   (The following 5 arrays must be in order from closest to the radar
!    to farthest...)
!   [hgt_matrix]      height of hydrometeors (km)
!   [hm_matrix]       table of hydrometeor mixing rations (g/kg)
!   [re_matrix]       OPTIONAL table of hydrometeor effective radii (microns)
!   [p_matrix]        pressure profile (hPa)
!   [t_matrix]        temperature profile (C)
!   [rh_matrix]       relative humidity profile (%)
!
! Outputs:
!   [Ze_non]          radar reflectivity without attenuation (dBZ)
!   [Ze_ray]          Rayleigh reflectivity (dBZ)
!   [h_atten_to_vol]  attenuation by hydromets, radar to vol (dB)
!   [g_atten_to_vol]  gaseous atteunation, radar to vol (dB)
!   [dBZe]            effective radar reflectivity factor (dBZ)
!
! Optional:
!   [g_to_vol_in]     integrated atten due to gases, r>v (dB).
!                     If present then is used as gaseous absorption, independently of the
!                     value in use_gas_abs
!   [g_to_vol_out]    integrated atten due to gases, r>v (dB).
!                     If present then gaseous absorption for each profile is returned here.
!
! Created:
!   11/28/2005  John Haynes (haynes@atmos.colostate.edu)
! Modified:
!   09/2006  placed into subroutine form, scaling factors (Roger Marchand,JMH)
!   08/2007  added equivalent volume spheres, Z and N scalling most distrubtion types (Roger Marchand)
!   01/2008  'Do while' to determine if hydrometeor(s) present in volume
!             changed for vectorization purposes (A. Bodas-Salcedo)

! ----- INPUTS -----  
  type(mie), intent(in) :: mt
  type(class_param), intent(inout) :: hp
  real*8, intent(in) :: freq,k2
  integer, intent(in) ::  do_ray,use_gas_abs,use_mie_table, &
    nhclass,nprof,ngate,nsizes
  real*8, dimension(nsizes), intent(in) :: D
  real*8, dimension(nprof,ngate), intent(in) :: hgt_matrix, p_matrix, &
    t_matrix,rh_matrix
  real*8, dimension(nhclass,nprof,ngate), intent(in) :: hm_matrix
  real*8, dimension(nhclass,nprof,ngate), intent(inout) :: re_matrix
    
! ----- OUTPUTS -----
  real*8, dimension(nprof,ngate), intent(out) :: Ze_non,Ze_ray, &
 	g_atten_to_vol,dBZe,h_atten_to_vol

! ----- OPTIONAL -----
  real*8, optional, dimension(ngate,nprof) :: &
  g_to_vol_in,g_to_vol_out ! integrated atten due to gases, r>v (dB). This allows to output and then input
                           ! the same gaseous absorption in different calls. Optional to allow compatibility
                           ! with original version. A. Bodas April 2008.
        
!  real*8, dimension(nprof,ngate) :: kr_matrix 

! ----- INTERNAL -----
  integer :: &
  phase, &			! 0=liquid, 1=ice
  ns 				! number of discrete drop sizes

  integer*4, dimension(ngate) :: &
  hydro				! 1=hydrometeor in vol, 0=none
  real*8 :: &
  rho_a, &			! air density (kg m^-3)
  gases				! function: 2-way gas atten (dB/km)

  real*8, dimension(:), allocatable :: &
  Di, Deq, &      		! discrete drop sizes (um)
  Ni, Ntemp, &    		! discrete concentrations (cm^-3 um^-1)
  rhoi				! discrete densities (kg m^-3)
  
  real*8, dimension(ngate) :: &
  z_vol, &			! effective reflectivity factor (mm^6/m^3)
  z_ray, &                      ! reflectivity factor, Rayleigh only (mm^6/m^3)
  kr_vol, &			! attenuation coefficient hydro (dB/km)
  g_vol, &			! attenuation coefficient gases (dB/km)
  a_to_vol, &			! integrated atten due to hydometeors, r>v (dB)
  g_to_vol			! integrated atten due to gases, r>v (dB)
   
 
  integer,parameter :: KR8 = selected_real_kind(15,300)
  real*8, parameter :: xx = -1.0_KR8
  real*8,  dimension(:), allocatable :: xxa
  real*8 :: kr, ze, zr, pi, scale_factor, tc, Re, ld, tmp1, ze2, kr2,apm,bpm
  integer*4 :: tp, i, j, k, pr, itt, iff

  real*8 bin_length,step,base,step_list(25),base_list(25)
  integer*4 iRe_type,n,max_bin
  
  logical :: g_to_vol_in_present, g_to_vol_out_present
	
  ! Logicals to avoid calling present within the loops
  g_to_vol_in_present  = present(g_to_vol_in)
  g_to_vol_out_present = present(g_to_vol_out)
  
    ! set up Re bins for z_scalling
	bin_length=50;
	max_bin=25

	step_list(1)=1
	base_list(1)=75 
	do j=2,max_bin
		step_list(j)=3*(j-1);
		if(step_list(j)>bin_length) then
			step_list(j)=bin_length;
		endif
		base_list(j)=base_list(j-1)+floor(bin_length/step_list(j-1));
	enddo


  pi = acos(-1.0)
  if (use_mie_table == 1) iff = infind(mt%freq,freq,sort=1)

	
  ! // loop over each profile (nprof)
  do pr=1,nprof

!   ----- calculations for each volume ----- 
    z_vol(:) = 0
    z_ray(:) = 0
    kr_vol(:) = 0
    hydro(:) = 0    

!   // loop over eacho range gate (ngate)
    do k=1,ngate
  
!     :: determine if hydrometeor(s) present in volume
      hydro(k) = 0
      do j=1,nhclass ! Do while changed for vectorization purposes (A. B-S)
        if ((hm_matrix(j,pr,k) > 1E-12) .and. (hp%dtype(j) > 0)) then
          hydro(k) = 1
          exit
        endif
      enddo

      if (hydro(k) == 1) then
!     :: if there is hydrometeor in the volume            

        rho_a = (p_matrix(pr,k)*100.)/(287*(t_matrix(pr,k)+273.15))

!       :: loop over hydrometeor type
        do tp=1,nhclass

          if (hm_matrix(tp,pr,k) <= 1E-12) cycle

	  phase = hp%phase(tp)
	  if(phase==0) then
		itt = infind(mt_ttl,t_matrix(pr,k))
  	  else
		itt = infind(mt_tti,t_matrix(pr,k))
      endif

	  ! calculate Re if we have an exponential distribution with fixed No ... precipitation type particle
	  if( hp%dtype(tp)==2 .and. abs(hp%p2(tp)+1) < 1E-8)  then

		apm=hp%apm(tp)
		bpm=hp%bpm(tp)

  		if ((hp%rho(tp) > 0) .and. (apm < 0)) then
    			apm = (pi/6)*hp%rho(tp)
    			bpm = 3.
  		endif

		tmp1 = 1./(1.+bpm)
		ld = ((apm*gamma(1.+bpm)*hp%p1(tp))/(rho_a*hm_matrix(tp,pr,k)*1E-3))**tmp1
		
		Re = 1.5E6/ld 
		
		re_matrix(tp,pr,k) = Re;

	  endif
  
	  if(re_matrix(tp,pr,k).eq.0) then

		iRe_type=1
		Re=0
	  else
		iRe_type=1
		Re=re_matrix(tp,pr,k)
		
		n=floor(Re/bin_length)
		if(n==0) then
			if(Re<25) then
				step=0.5
				base=0
			else			
				step=1
				base=25
			endif
		else
			if(n>max_bin) then
				n=max_bin	
			endif

			step=step_list(n)
			base=base_list(n)
		endif

		iRe_type=floor(Re/step)

		if(iRe_type.lt.1) then  
			iRe_type=1			
		endif

		Re=step*(iRe_type+0.5)
		iRe_type=iRe_type+base-floor(n*bin_length/step)

	 	! make sure iRe_type is within bounds
		if(iRe_type.ge.nRe_types) then  

			! print *, tp, re_matrix(tp,pr,k), Re, iRe_type

			! no scaling allowed
			Re=re_matrix(tp,pr,k)

			iRe_type=nRe_types
			hp%z_flag(tp,itt,iRe_type)=.false.
			hp%scaled(tp,iRe_type)=.false.			
		endif
	  endif
	
  	  ! use Ze_scaled, Zr_scaled, and kr_scaled ... if know them
	  ! if not we will calculate Ze, Zr, and Kr from the distribution parameters
  	  if( .not. hp%z_flag(tp,itt,iRe_type) )  then
 	 
!         :: create a distribution of hydrometeors within volume	  
	  select case(hp%dtype(tp))
          case(4)
	    ns = 1
	    allocate(Di(ns),Ni(ns),rhoi(ns),xxa(ns),Deq(ns))
	    if (use_mie_table == 1) allocate(mt_qext(ns),mt_qbsca(ns),Ntemp(ns))
	    Di = hp%p1(tp)
	    Ni = 0.
	  case default
 	    ns = nsizes            
	    allocate(Di(ns),Ni(ns),rhoi(ns),xxa(ns),Deq(ns))
	    if (use_mie_table == 1) allocate(mt_qext(ns),mt_qbsca(ns),Ntemp(ns))	    
 	    Di = D
 	    Ni = 0.
	  end select

!         :: create a DSD (using scaling factor if applicable)
	  ! hp%scaled(tp,iRe_type)=.false.   ! turn off N scaling

	  call dsd(hm_matrix(tp,pr,k),Re,Di,Ni,ns,hp%dtype(tp),rho_a, &
	    t_matrix(pr,k),hp%dmin(tp),hp%dmax(tp),hp%apm(tp),hp%bpm(tp), &
	    hp%rho(tp),hp%p1(tp),hp%p2(tp),hp%p3(tp),hp%fc(tp,1:ns,iRe_type), &
	    hp%scaled(tp,iRe_type))

!         :: calculate particle density 
          ! if ((hp%rho_eff(tp,1,iRe_type) < 0) .and. (phase == 1)) then
	  if (phase == 1) then
	    if (hp%rho(tp) < 0) then
                
		! MG Mie approach - adjust density of sphere with D = D_characteristic to match particle density		
		! hp%rho_eff(tp,1:ns,iRe_type) = (6/pi)*hp%apm(tp)*(Di*1E-6)**(hp%bpm(tp)-3)   !MG Mie approach
		
		! as the particle size gets small it is possible that the mass to size relationship of 
		! (given by power law in hclass.data) can produce impossible results 
		! where the mass is larger than a solid sphere of ice.  
		! This loop ensures that no ice particle can have more mass/density larger than an ice sphere.
		! do i=1,ns
		! if(hp%rho_eff(tp,i,iRe_type) > 917 ) then
		!	hp%rho_eff(tp,i,iRe_type) = 917
		!endif
		!enddo

		! alternative is to use equivalent volume spheres.
	    	hp%rho_eff(tp,1:ns,iRe_type) = 917  				! solid ice == equivalent volume approach
	      	Deq = ( ( 6/pi*hp%apm(tp)/917 ) ** (1.0/3.0) ) * &
			   ( (Di*1E-6) ** (hp%bpm(tp)/3.0) )  * 1E6 		! Di now really Deq in microns.
		
            else

            	! hp%rho_eff(tp,1:ns,iRe_type) = hp%rho(tp)   !MG Mie approach
	     	
		! Equivalent volume sphere (solid ice rho_ice=917 kg/m^3).
	     	hp%rho_eff(tp,1:ns,iRe_type) = 917
	     	Deq=Di * ((hp%rho(tp)/917)**(1.0/3.0))  

	    endif

		! if using equivalent volume spheres
		if (use_mie_table == 1) then

			Ntemp=Ni

			! Find N(Di) from N(Deq) which we know
			do i=1,ns
                     		j=infind(Deq,Di(i))
				Ni(i)=Ntemp(j)
	        	enddo
		else
			! just use Deq and D variable input to mie code
			Di=Deq;
		endif

	  endif
	  rhoi = hp%rho_eff(tp,1:ns,iRe_type)
	  
!         :: calculate effective reflectivity factor of volume
	  if (use_mie_table == 1) then
	  
	    if ((hp%dtype(tp) == 4) .and. (hp%idd(tp) < 0)) then
              hp%idd(tp) = infind(mt%D,Di(1))
	    endif
	    
	    if (phase == 0) then
	    
	      ! itt = infind(mt_ttl,t_matrix(pr,k))
              select case(hp%dtype(tp))
	      case(4)
		mt_qext(1) = mt%qext(hp%idd(tp),itt,1,iff)
	        mt_qbsca(1) = mt%qbsca(hp%idd(tp),itt,1,iff)
              case default
  	        mt_qext = mt%qext(:,itt,1,iff)
	        mt_qbsca = mt%qbsca(:,itt,1,iff)
	      end select

          call zeff(freq,Di,Ni,ns,k2,mt_ttl(itt),0,do_ray, &
	        ze,zr,kr,mt_qext,mt_qbsca,xx)
	    
	    else

	      ! itt = infind(mt_tti,t_matrix(pr,k))
	      select case(hp%dtype(tp))
	      case(4)
                if (hp%ifc(tp,1,iRe_type) < 0) then
                  hp%ifc(tp,1,iRe_type) = infind(mt%f,rhoi(1)/917.)
 	        endif	   	      
                mt_qext(1) = &
		  mt%qext(hp%idd(tp),itt+cnt_liq,hp%ifc(tp,1,iRe_type),iff)
	        mt_qbsca(1) = &
		  mt%qbsca(hp%idd(tp),itt+cnt_liq,hp%ifc(tp,1,iRe_type),iff)	      
	      case default
 	        do i=1,ns
 	          if (hp%ifc(tp,i,iRe_type) < 0) then
                    hp%ifc(tp,i,iRe_type) = infind(mt%f,rhoi(i)/917.)
 	          endif	      
       	          mt_qext(i) = mt%qext(i,itt+cnt_liq,hp%ifc(tp,i,iRe_type),iff)
		  mt_qbsca(i) = mt%qbsca(i,itt+cnt_liq,hp%ifc(tp,i,iRe_type),iff)
	        enddo
	      end select

		   call zeff(freq,Di,Ni,ns,k2,mt_tti(itt),1,do_ray, &
	        ze,zr,kr,mt_qext,mt_qbsca,xx)

	    endif

	  else
       
	    xxa = -9.9
	    call zeff(freq,Di,Ni,ns,k2,t_matrix(pr,k),phase,do_ray, &
	      ze,zr,kr,xxa,xxa,rhoi)

	      
	  endif  ! end of use mie table 

		! xxa = -9.9
	    	!call zeff(freq,Di,Ni,ns,k2,t_matrix(pr,k),phase,do_ray, &
	      	!	ze2,zr,kr2,xxa,xxa,rhoi)

		! if(abs(ze2-ze)/ze2 > 0.1) then
  		! if(abs(kr2-kr)/kr2 > 0.1) then
  		
		! write(*,*) pr,k,tp,ze2,ze2-ze,abs(ze2-ze)/ze2,itt+cnt_liq,iff
		! write(*,*) pr,k,tp,ze2,kr2,kr2-kr,abs(kr2-kr)/kr2
		! stop

		!endif

	  deallocate(Di,Ni,rhoi,xxa,Deq)
  	  if (use_mie_table == 1) deallocate(mt_qext,mt_qbsca,Ntemp)

	  else ! can use z scaling
	  
		if( hp%dtype(tp)==2 .and. abs(hp%p2(tp)+1) < 1E-8 )  then
		 
			ze = hp%Ze_scaled(tp,itt,iRe_type)
			zr = hp%Zr_scaled(tp,itt,iRe_type)
			kr = hp%kr_scaled(tp,itt,iRe_type)

		else
	    		scale_factor=rho_a*hm_matrix(tp,pr,k) 

			zr = hp%Zr_scaled(tp,itt,iRe_type) * scale_factor 
			ze = hp%Ze_scaled(tp,itt,iRe_type) * scale_factor
			kr = hp%kr_scaled(tp,itt,iRe_type) * scale_factor	
		endif

	  endif  ! end z_scaling
 
	  ! kr=0 

	  kr_vol(k) = kr_vol(k) + kr
	  z_vol(k) = z_vol(k) + ze
	  z_ray(k) = z_ray(k) + zr
	
	  ! construct Ze_scaled, Zr_scaled, and kr_scaled ... if we can
	  if( .not. hp%z_flag(tp,itt,iRe_type) .and. 1.eq.1 ) then

		if( ( (hp%dtype(tp)==1 .or. hp%dtype(tp)==5 .or.  hp%dtype(tp)==2)  .and. abs(hp%p1(tp)+1) < 1E-8  ) .or. &
		    (  hp%dtype(tp)==3 .or. hp%dtype(tp)==4 )  &
		) then

			scale_factor=rho_a*hm_matrix(tp,pr,k) 

			hp%Ze_scaled(tp,itt,iRe_type) = ze/ scale_factor
			hp%Zr_scaled(tp,itt,iRe_type) = zr/ scale_factor
			hp%kr_scaled(tp,itt,iRe_type) = kr/ scale_factor

			hp%z_flag(tp,itt,iRe_type)=.True.

		elseif( hp%dtype(tp)==2 .and. abs(hp%p2(tp)+1) < 1E-8 ) then 
		 
			hp%Ze_scaled(tp,itt,iRe_type) = ze
			hp%Zr_scaled(tp,itt,iRe_type) = zr
			hp%kr_scaled(tp,itt,iRe_type) = kr

			hp%z_flag(tp,itt,iRe_type)=.True.
		endif

	  endif

        enddo	! end loop of tp (hydrometeor type)

      else
!     :: volume is hydrometeor-free
	
        kr_vol(k) = 0
	z_vol(k) = -999
        z_ray(k) = -999
	
      endif

!     :: attenuation due to hydrometeors between radar and volume
      a_to_vol(k) = 2*path_integral(kr_vol,hgt_matrix(pr,:),1,k-1)
      
!     :: attenuation due to gaseous absorption between radar and volume
      if (g_to_vol_in_present) then
        g_to_vol(k) = g_to_vol_in(k,pr)
      else
        if ( (use_gas_abs == 1) .or. ((use_gas_abs == 2) .and. (pr == 1)) )  then
            g_vol(k) = gases(p_matrix(pr,k),t_matrix(pr,k)+273.15, &
            rh_matrix(pr,k),freq)
            g_to_vol(k) = path_integral(g_vol,hgt_matrix(pr,:),1,k-1)
        elseif (use_gas_abs == 0) then
            g_to_vol(k) = 0
        endif  
      endif
    
!      kr_matrix(pr,:)=kr_vol

!     :: store results in matrix for return to calling program
      h_atten_to_vol(pr,k)=a_to_vol(k)
      g_atten_to_vol(pr,k)=g_to_vol(k)
      if ((do_ray == 1) .and. (z_ray(k) > 0)) then
        Ze_ray(pr,k) = 10*log10(z_ray(k))
      else
        Ze_ray(pr,k) = -999
      endif
      if (z_vol(k) > 0) then
        dBZe(pr,k) = 10*log10(z_vol(k))-a_to_vol(k)-g_to_vol(k)
        Ze_non(pr,k) = 10*log10(z_vol(k))
      else
        dBZe(pr,k) = -999
        Ze_non(pr,k) = -999
      endif
      
    enddo	! end loop of k (range gate)
    ! Output array with gaseous absorption
    if (g_to_vol_out_present) g_to_vol_out(:,pr) = g_to_vol
  enddo		! end loop over pr (profile)  

  end subroutine radar_simulator