;===========================================================
;         Constants to be made GLOBALly available.
;===========================================================
; This serves the purpose of having in one place
; commonly used constants and conversion factors.
; The purpose of the awkward (CAP)_C is to try to ensure 
; that the variable names will be unique.
;
; N[ewton]     kg-m/s2        ; force                
; J[oule]      kg-m2/s2       ; energy           
; Pa           kg/(m-s2)=N/m2 ; pressure    
; hPa=mb       Pa*0.01
; W[att]       kg-m2/s3 =J/s  ; power      
; l[iter]      1e-3 m3
; 1 J[oule]   = 1e7 ergs      ; 1 erg = 1e-7 J
; 1 J[oule]   = 0.238846 cal[ories]
; 1 cal[orie] = 4.1868   J[oules]  ==> 4.1868e7 ergs
; 1 langley   = 1 gm-calorie/cm2 = 41.84 kilojoules per square meter (kJ/m2)
; 1 langley   = 41849.        ; [J/m2]
;
; kg/m2       => mm        ; [kg/m2][1000 mm/m][(1/1000) m3/kg] ==> mm

  GRAV_C  = 9.80665        ; [m/s] gravity at 45 deg lat used by the WMO
  OMEGA_C = 7.292e-05      ; [1/s] earth's angular vel 
  RE_C    = 6.37122e06     ; [m]   average radius of earth
  PI_C    = 4.*atan(1.)    ; pi
  RAD_C   = PI_C/180.      ; [radian/degree] convert degrees to radians

                           ; spc heat capacities [Hess, pg 24]
  CP_C    = 1004.          ; [J/(K kg)] <==> [ m2/(K s2) ] dry air constant p
  CV_C    = 717.           ; [J/(K kg)] <==> [ m2/(K s2) ] dry air constant vol
  CSW2_C  = 951.           ; sea water [salinity @ 2%  SST= 17.5C]
  CSW4_C  = 926.           ; sea water [salinity @ 4%  SST= 17.5C]
  CICE_C  = 503.           ; pure ice  [salinity @ 0%  SST=  0.0C]
                           
  SOLAR_C = 2.0            ; langley/min
  LAT2M_C = 111.1e3        ; [m]     1 degree of latitude in meters 

  CLIGHT_C= 2.99792e8      ; [m/s]
  RD_C    = 287.           ; [J/(K-kg)] Gas Constant dry air
  RV_C    = 461.           ; [J/(K-kg)] Gas Constant water vapor

                           ; latent heat [Wallace - Hobbs]
; LV_C    = 2.5104e6       ; [J/kg]=[m2/s2]  Latent Heat of Vaporization of Water
  LV_C    = 2.26e6         ; [J/kg]=[m2/s2]  Latent Heat of Vaporization
  LV100_C = 2.25e6         ; [J/kg]=[m2/s2]  latent heat of vaporization at 100C
  LF_C    = 3.34e5         ; [J/kg]=[m2/s2]  latent heat of fusion at 0C

  MD_C    = 28.97          ; unitless; molecular weight dry air

  D_H2O_C  = 1000          ; [kg/m3] Density of Liquid Water at 4C
  D_AIR_C  = 1.275         ; [kg/m3] Density of Dry Air at 1000mb and 0C [varies as p/T] 
  TC_AIR_C = 0.240         ; [J/(m s2 K)] Thermal conductivity of dry air at 0C

  SB_C     = 5.6696e-8     ; [W/(m2 K4)] Stefan_Boltzmann constant
  SECDAY_C = 86400.        ; [s/day] = [s/24hr]

                           ; To convert units kg/(m2-s) to mm/day 
                           ; multiply by (10^3mm m-1 x 86400 s day-1) and 
                           ; divide by density_H2O (1000 kg m-3). 
  CON_A    = 86400.        ; [kg/m2-s][1000 mm/m][86400 s/day][(1/1000) m3/kg] ==> mm/day

                           ; To convert mm/day to W/m2 [(kg/s3)]
                           ; multiply by (density_H2O x L) and 
                           ; divide by (10^3mm m-1 x 86400 s day-1).
  CON_B    = LV_C/SECDAY_C ; [mm/day][1000 kg/m3][2.51e6 m2/s2][(1/1000) m/mm][(1/86400) day/s] ==> kg/s3 =>W/m2
                           ; molecular weight of dry air 28.97
                           ; molecular weight of water vapor 18.016

; http://www.ssec.wisc.edu/~paulv/Fortran90/Profile_Utility/Units_Conversion.f90.html#PPMV_TO_MR
                           ;                                  MW(MOL) 
                           ; mr(MOL) = 0.001 . ppmv(MOL) . -------------
                           ;                                MW(Dry Air)
                           ; where MW(Dry Air) = Average molecular weight of dry air 
                           ;       MW(MOL)     = Molecular weight of the gas in question.
                           ;
                           ; The factor of 0.001 derives from the product of the g/g to g/kg. 
                           ;       scale factor (1000) and the "parts-per-million" to 
                           ;      "parts-per" scale factor (1.0e-06)

  CON_C    = (28.97/18.016); ppmv to ppmm [g/kg]    
  CON_D    = CON_C*0.001   ; kg/kg