! $Id: ropp_apps_constants.f90 4512 2015-04-28 14:21:22Z idculv $

MODULE ropp_apps_constants

!****m* Modules/ropp_apps_constants *
!
! NAME
!    ropp_apps_constants - Module providing meteorological and physical constants.
!
! SYNOPSIS
!    use ropp_apps_constants
! 
! DESCRIPTION
!    This module provides numerical values for meteorological and other
!    physical constants which are used throughout the ROPP package.
!
! SEE ALSO
!
!    Thermodynamic constants:    R_dry, R_vap, C_p,
!                                epsilon_water,
!                                t_allice, t_freeze, t_triple
!                                svp_freeze
!
!    Geodetic constants:         g_wmo
!
!    Refractivity constants:     kappa1, kappa2
!
!    Mathematical constants:     pi, dtor
!
! AUTHOR
!   Met Office, Exeter, UK.
!   Any comments on this software should be given via the ROM SAF
!   Helpdesk at http://www.romsaf.org
!
! COPYRIGHT
!   Copyright (c) 1998-2010 Michael Gorbunov <michael.gorbunov@zmaw.de>
!   For further details please refer to the file COPYRIGHT
!   which you should have received as part of this distribution.
!
!****

  USE typesizes, ONLY: wp => EightByteReal

  IMPLICIT NONE


!-------------------------------------------------------------------------------
! 1. Thermodynamical constants
!-------------------------------------------------------------------------------

!****t* Constants/Thermal
!
! DESCRIPTION
!    Thermodynamic constants relating to air/water properties.
!
! SEE ALSO
!
!****

!****p* Thermodynamics/R_dry *
!
! NAME
!    R_dry - Gas constant of dry air
!
! SOURCE
!
!!  REAL(wp), PARAMETER :: R_dry = 287.0597_wp        !   J K^{-1} kg^{-1}
  REAL(wp), PARAMETER :: R_dry = 287.05_wp        !   J K^{-1} kg^{-1}
!
!****

!****p* Thermodynamics/C_p *
!
! NAME
!    C_p - Specific heat capacity of dry air at constant pressure
!
! SOURCE
!
!!  REAL(wp), PARAMETER :: C_p = 1005.7_wp       !   J K^{-1} kg^{-1}
  REAL(wp), PARAMETER :: C_p = 1004.6_wp       !   J K^{-1} kg^{-1}
!
!****

!****p* Thermodynamics/epsilon_water *
!
! NAME
!    epsilon_water - Ratio of molecular weight of water to that of dry air.
!
! SOURCE
!
  REAL(wp), PARAMETER :: epsilon_water = 0.621981_wp  !mw_water / mw_dry_air
!
!****

!****p* Thermodynamics/t_allice *
!
! NAME
!    t_allice - lowest temperature of mixed phase region, below
!               which it is all considered to be ice.
!
! SOURCE
!
  REAL(wp), PARAMETER :: t_allice = 250.16_wp ! allice point [K]
!
!****

!****p* Thermodynamics/t_freeze *
!
! NAME
!    t_freeze - Freezing point of water.
!
! SOURCE
!
  REAL(wp), PARAMETER :: t_freeze = 273.15_wp ! freezing point [K]
!
!****

!****p* Thermodynamics/t_triple *
!
! NAME
!    t_triple - Triple point of water.
!
! SOURCE
!
  REAL(wp), PARAMETER :: t_triple = 273.16_wp ! triple point [K]
!
!****

!****p* Thermodynamics/svp_freeze *
!
! NAME
!    t_freeze - Saturated vapour pressure of water at freezing point.
!
! SOURCE
!
  REAL(wp), PARAMETER :: svp_freeze = 611.21_wp ! svp at freezing point [Pa]
!
!****


!-------------------------------------------------------------------------------
! 2. Geodetic constants
!-------------------------------------------------------------------------------

!****t* Constants/Earth
!
! DESCRIPTION
!    Geodetic constants relating to geopotentials.
!
!****

!****p* Earth/g_wmo *
!
! NAME
!    g_wmo - Gravitational acceleration (WMO standard value)
!
! SOURCE
!
  REAL(wp), PARAMETER :: g_wmo = 9.80665_wp         !   m s^{-2}
!
!****


!-------------------------------------------------------------------------------
! 3. RO specific constants
!-------------------------------------------------------------------------------

!****t* Constants/RadioOccultation
!
! DESCRIPTION
!    Physical constants specific for radio occultation measurement as used in
!    the ROPP Forward Model library.
!
! SEE ALSO
!    kappa1
!    kappa2
!
!****

!****p* RadioOccultation/kappa1 *
!
! NAME
!    kappa1 - Coefficient to calculate dry refractivity contribution.
!
! SOURCE
!
  REAL(wp), PARAMETER :: kappa1 = 77.60e-2_wp      !   K Pa^{-1}
!
!****

!****p* RadioOccultation/kappa2 *
!
! NAME
!    kappa2 - Coefficient to calculate moist refractivity contribution.
!
! SOURCE
!
  REAL(wp), PARAMETER :: kappa2 = 3.73e3_wp        !   K^2 Pa^{-1}
!
!****

!-------------------------------------------------------------------------------
! 4. Mathematical constants
!------------------------------------------------------------------------------

!****t* Constants/Maths
!
! DESCRIPTION
!    Mathematical constants.
!
!****

!****p* Maths/pi *
!
! NAME
!    pi
!
! SOURCE
!
  REAL(wp), PARAMETER :: pi = 3.141592653589793238_wp
!
!****

!****p* Maths/dtor *
!
! NAME
!    dtor = pi/180
!
! SOURCE
!
  REAL(wp), PARAMETER :: dtor = pi / 180.0_wp
!
!****

END MODULE ropp_apps_constants