Units Conversion
Subprogram Descriptions
SA_TO_MR
NAME:
SA_to_MR
PURPOSE:
Function to convert gas specific amounts to mass mixing ratio
CALLING SEQUENCE:
Mixing_Ratio = SA_to_MR( Specific_Amount, & ! Input
Water_Vapor=Water_Vapor, & ! Optional input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Specific_Amount: Gas specific amount comcentration.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor mass mixing ratio. If this argument is
not supplied, the mandatory input SPECIFIC_AMOUNT
argument is assumed to be water vapor.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Mixing_Ratio: The gas mass mixing ratio. If an error occurs,
the value -1.0 is returned.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as input Specific_Amount
PROCEDURE:
The specific amount is defined as the ratio of the mass of gas
to the total mass of air and water vapor in a given volume:
Mg
SA = --------- .......(1)
Md + Mw
where Mg = mass of gas
Mw = mass of water vapor
Md = mass of dry air (including Mg).
The gas mass mixing ratio is defined as the ratio of the mass
of the gas to the mass of dry air in a given volume:
Mg
MRg = ---- .......(2)
Md
Rearranging (1) and substituting in (2) gives,
1 Md + Mw
---- = ---------
SA Mg
Md Mw
= ---- + ----
Mg Mg
Md Mw Md Md
= ---- + ----.---- ( multiplying the second term by ---- )
Mg Md Mg Md
1
= ----- ( 1 + MRw )
MRg
therefore,
MRg = SA ( 1 + MRw )
for input units of g/g or kg/kg. For input units of g/kg then,
MRg = SA ( 1 + 0.001*MRw ) .......(3)
If the input specific amount is for water vapor (specific humidity)
then (3) becomes,
MRw = SA ( 1 + 0.001*MRw )
i.e.
MRw = SA + 0.001*MRw*SA
i.e.
MRw( 1 - 0.001*SA ) = SA
therefore,
SA
MRw = ------------------ .......(4)
( 1 - 0.001*SA )
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 05-Dec-2003
paul.vandelst@ssec.wisc.edu
MR_TO_SA
NAME:
MR_to_SA
PURPOSE:
Function to convert gas concentrations from mass mixing ratio to
specific amounts.
CATEGORY:
Profile Utility
LANGUAGE:
Fortran-95
CALLING SEQUENCE:
Specific_Amount = MR_to_SA( Mixing_Ratio, & ! Input
Water_Vapor=Water_Vapor, & ! Optional input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Mixing_Ratio: Gas mass mixing ratio.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor specific humidity. If this argument is
not supplied, the mandatory input MIXING_RATIO
argument is assumed to be water vapor.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Specific_Amount: The gas specific amount. If an error occurs,
the value -1.0 is returned.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as input Mixing_Ratio
PROCEDURE:
From the SA_to_MR conversion, we know that for input units of
g/kg that,
MRg = SAg ( 1 + 0.001*MRw ) .......(1)
and
SAw
MRw = ------------------- .......(2)
( 1 - 0.001*SAw )
where MRg = mass mixing ratio of gas
MRw = mass mixing ratio of water vapor
SAg = specific amount of gas
SAw = specific amount of water vapor (specific humidity)
Rearranging (1) and (2) gives,
SAg = MRg ( 1 - 0.001*SAw )
and for water vapor only,
MRw
SAw = -------------------
( 1 + 0.001*MRw )
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 05-Dec-2003
paul.vandelst@ssec.wisc.edu
RH_TO_MR
NAME:
RH_to_MR
PURPOSE:
Function to convert relative humidity to water vapor mixing ratio
CALLING SEQUENCE:
Mixing_Ratio = RH_to_MR( Pressure, & ! Input
Temperature, & ! Input
Relative_Humidity, & ! Input
Ice_Temperature=Ice_Temperature, & ! optional input
Min_Pressure =Min_Pressure, & ! Optional input
Message_Log =Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature.
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
Relative_Humidity: Atmospheric relative humidity.
UNITS: %
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Ice_Temperature: Temperature below which the saturation vapor
pressure over ice is used in the conversion.
By default, only the saturation vapor pressure
over water is used.
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Min_Pressure: Pressure value below which the saturation
mixing ratio is not calculated. The default
is 50mb. Saturation mixing ratios below the
minimum pressure are set to zero. This is
because at pressures less than 50mb, the
saturation vapour Pressure, which is based
only on temperature, can exceed the total
air Pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Mixing_Ratio: Water vapor mass mixing ratio. If an error occurs,
-1.0 is returned.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
Once the saturation mixing ratio is calculated the mixing ratio
corresponding to the input relative humidity is determined using:
Relative_Humidity * Saturation_Mixing_Ratio
Mixing_Ratio = ———————————————
100
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 02-Mar-1999
paul.vandelst@ssec.wisc.edu
MR_TO_RH
NAME:
MR_to_RH
PURPOSE:
Function to convert water vapor mixing ratio to relative humidity
CALLING SEQUENCE:
Relative_Humidty = MR_to_RH( Pressure, & ! Input
Temperature, & ! Input
Mixing_Ratio, & ! Input
Ice_Temperature=Ice_Temperature, & ! optional input
Min_Pressure =Min_Pressure, & ! Optional input
Message_Log =Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature.
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
Mixing_Ratio: Water vapor mixing ratio.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Ice_Temperature: Temperature below which the saturation vapor
pressure over ice is used in the conversion.
By default, only the saturation vapor pressure
over water is used.
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Min_Pressure: Pressure value below which the saturation
mixing ratio is not calculated. The default
is 50mb. Saturation mixing ratios below the
minimum pressure are set to zero. This is
because at pressures less than 50mb, the
saturation vapour Pressure, which is based
only on temperature, can exceed the total
air Pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Relative_Humidity: Relative humidity. If an error occurs,
-1.0 is returned.
UNITS: %
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
Once the saturation mixing ratio is calculated the relative humidity
corresponding to the input mixing ratio is determined using:
Mixing_Ratio
Relative_Humidity = 100.0 * -------------------------
Saturation_Mixing_Ratio
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 02-Mar-1999
paul.vandelst@ssec.wisc.edu
MR_TO_PPMV
NAME:
MR_to_PPMV
PURPOSE:
Function to convert gas concentrations from mass mixing ratio in g/kg
to volume mixing ratio in ppmv
CALLING SEQUENCE:
ppmv = MR_to_PPMV( Mixing_Ratio, & ! Input
Molecule_ID=Molecule_ID, & ! Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Mixing_Ratio: Mass mixing ratio of gas.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Molecule_ID: HITRAN molecular designation identifying the
molecule for which the concentration units
conversion is required. If not specified, the
default value is that for water vapor.
Valid values are:
1: H2O 9: SO2 17: HI 25: H2O2
2: CO2 10: NO2 18: ClO 26: C2H2
3: O3 11: NH3 19: OCS 27: C2H6
4: N2O 12: HNO3 20: H2CO 28: PH3
5: CO 13: OH 21: HOCl 29: COF2
6: CH4 14: HF 22: N2 30: SF6
7: O2 15: HCl 23: HCN 31: H2S
8: NO 16: HBr 24: CH3Cl 32: HCOOH
UNITS: N/A
TYPE: INTEGER
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
ppmv: Volume mixing ratio of gas. If an error occurs,
-1.0 is returned.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as input Mixing_Ratio
PROCEDURE:
To convert mixing ratio in g/kg to parts-per-million, the following
is used:
MW(Dry Air)
ppmv(MOL) = 1000 . Mixing_Ratio(MOL) . ————-
MW(MOL)
where MW(Dry Air) = Average molecular weight of dry air
MW(MOL) = Molecular weight of the gas in question.
The factor of 1000 derives from the product of the g/kg to g/g
scale factor (0.001) and the “parts-per” to “parts-per-million”
scale factor (1.0e+06)
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 03-May-2000
paul.vandelst@ssec.wisc.edu
PPMV_TO_MR
NAME:
PPMV_to_MR
PURPOSE:
Function to convert gas concentrations from volume mixing ratio in
ppmv to mass mixing ratio in g/kg.
CALLING SEQUENCE:
Mixing_Ratio = PPMV_to_MR( ppmv, & ! Input
Molecule_ID=Molecule_ID, & ! Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
ppmv: Volume mixing ratio of gas.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Molecule_ID: HITRAN molecular designation identifying the
molecule for which the concentration units
conversion is required. If not specified, the
default value is that for water vapor.
Valid values are:
1: H2O 9: SO2 17: HI 25: H2O2
2: CO2 10: NO2 18: ClO 26: C2H2
3: O3 11: NH3 19: OCS 27: C2H6
4: N2O 12: HNO3 20: H2CO 28: PH3
5: CO 13: OH 21: HOCl 29: COF2
6: CH4 14: HF 22: N2 30: SF6
7: O2 15: HCl 23: HCN 31: H2S
8: NO 16: HBr 24: CH3Cl 32: HCOOH
UNITS: N/A
TYPE: INTEGER
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Mixing_Ratio: Mass mixing ratio of gas. If an error occurs,
-1.0 is returned.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as input ppmv
PROCEDURE:
To convert ppmv to mixing ratio, the following is used:
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)
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 03-May-2000
paul.vandelst@ssec.wisc.edu
PPMV_TO_PP
NAME:
PPMV_to_PP
PURPOSE:
Function to convert gas concentrations from ppmv to partial pressure
CALLING SEQUENCE:
Partial_Pressure = PPMV_to_PP( Pressure, & ! Input
ppmv, & ! Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
ppmv: Gas volume mixing ratio in ppmv.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor partial pressure. If this argument is
not supplied, the mandatory input PPMV argument is
assumed to be water vapor.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Partial_Pressure: Gas partial pressure. If an error occurs,
-1.0 is returned.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
To convert volume mixing ratio in ppmv of a molecular species,
designated by MOL, to partial pressure, the following is used,
pp(MOL) = 1.0e-06 . ppmv(MOL) . ( Pressure - pp(H2O) )
If the input molecule is water vapor, the partial pressure is
determined using,
1
pp(H2O) = 1.0e-06 . ppmv(H2O) . Pressure . -----------------------------
1 + ( 1.0e-06 . ppmv(H20) )
This is based on the same methods used in the LBLRTM conversion code
in its lblatm.f module where molecular mixing ratios (either ppmv or
g/kg) are always with respect to DRY AIR.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 03-May-2000
paul.vandelst@ssec.wisc.edu
PP_TO_PPMV
NAME:
PP_to_PPMV
PURPOSE:
Function to convert gas concentrations from partial pressure to
volume mixing ratio in ppmv
CALLING SEQUENCE:
ppmv = PP_to_PPMV( Pressure, & ! Input
Partial_Pressure, & ! Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Partial_Pressure: Gas partial pressure
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor volume mixing ratio. If this argument is
not supplied, the mandatory Partial_Pressure argument
is assumed to be water vapor.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
ppmv: Gas volume mixing ratio. If an error occurs,
-1.0 is returned.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
To convert the partial pressure of a molecular species, designated
by MOL, to volume mixing ratio in ppmv, the following is used,
pp(MOL)
ppmv(MOL) = 1.0e+06 . ------------------
Dry_Air_Pressure
where
1
Dry_Air_Pressure = Pressure . ----------------------------
1 + ( ppmv(H2O) . 1.0e-6 )
If the input molecule is water vapor, the dry air pressure is
determined simply using,
Dry_Air_Pressure = Pressure - pp(H2O)
This is based on the same methods used in the LBLRTM conversion code
in its lblatm.f module where molecular mixing ratios (either ppmv or
g/kg) are always with respect to DRY AIR.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 03-May-2000
paul.vandelst@ssec.wisc.edu
MR_TO_PP
NAME:
MR_to_PP
PURPOSE:
Function to convert gas concentrations from mixing ratio in g/kg
to partial pressure in hectoPascals.
CALLING SEQUENCE:
Partial_Pressure = MR_to_PP( Pressure, & ! Input
Mixing_Ratio, & ! Input
Molecule_ID=Molecule_ID, & ! Optional Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Mixing_Ratio: Mass mixing ratio of gas.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Molecule_ID: HITRAN molecular designation identifying the
molecule for which the concentration units
conversion is required. If not specified, the
default value is that for water vapor.
Valid values are:
1: H2O 9: SO2 17: HI 25: H2O2
2: CO2 10: NO2 18: ClO 26: C2H2
3: O3 11: NH3 19: OCS 27: C2H6
4: N2O 12: HNO3 20: H2CO 28: PH3
5: CO 13: OH 21: HOCl 29: COF2
6: CH4 14: HF 22: N2 30: SF6
7: O2 15: HCl 23: HCN 31: H2S
8: NO 16: HBr 24: CH3Cl 32: HCOOH
UNITS: N/A
TYPE: INTEGER
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Water_Vapor: Water vapor partial pressure. If this argument is
not supplied, the mandatory MIXING_RATIO argument
is assumed to be water vapor.
This argument is ignored if the specified or default
molecule ID is set to 1.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Partial_Pressure: Gas partial pressure. If an error occurs,
-1.0 is returned.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
First a definition. In this routine, the mass mixing ratio of a gas
is defined to be, for a given volume, the ratio of the mass of the gas
in question to that of DRY air.
The ideal gas equation can be written as,
p = n.R0.T ................................................(1)
for unit volume, where
n = number of moles of gas,
R0 = universal gas constant
T = temperature.
The mass mixing ratio of a gas is defined as the mass of the gas with
respect to the mass of dry air in the same volume. If we use eqn(1)
to construct expressions for the partial pressures of a particular
gas and dry air, we get,
pp(MOL) = n(MOL).R0.T .................................(2a)
and
pp(DryAir) = n(DryAir).R0.T ..............................(2b)
Dividing eqn(2a) by (2b) and rearranging we get,
n(MOL)
pp(MOL) = ----------- . pp(DryAir) ........................(3)
n(DryAir)
Replacing the expssion for the number of moles of a substance into
eqn(3) gives us,
m(MOL) MW(DryAir)
pp(MOL) = --------- . ------------ . pp(DryAir)
MW(MOL) m(DryAir)
m(MOL) MW(DryAir)
= ----------- . ------------ . pp(DryAir)
m(DryAir) MW(MOL)
MW(DryAir)
= 0.001 . w(MOL) . ------------ . pp(DryAir) ......(4)
MW(MOL)
where m(MOL) = mass of gas MOL in grams,
m(DryAir) = mass of dry air in grams,
MW(MOL) = molecular weight of of gas MOL in grams,
MW(DryAir) = effective molecular weight of dry air in grams,
w(MOL) = mass mixing ratio of gas MOL in g/kg.
The factor of 0.001 in eqn(4) is to convert the units of the mixing
ratio from g/kg to g/g.
Two cases need to be addressed:
-------------
1) MOL == H2O
-------------
If the gas for which the mixing ratio is to be converted is water
vapor, then eqn(4) can be written as,
pp(H2O) = WX . ( p(Total) - pp(H2O) ) .....................(5)
MW(DryAir)
where WX = 0.001 . w(H2O) . ------------
MW(H2O)
Expanding eqn(5) further, we get
pp(H2O) = ( WX . p(Total) ) - ( WX . pp(H2O) )
and,
pp(H2O) . ( 1 + WX ) = WX . p(Total)
and finally,
WX
pp(H2O) = ------------ . p(Total) .........................(6)
( 1 + WX )
Eqn(6) is used to determine the partial pressure for water vapor
input in this routine.
-------------------
2) MOL is *not* H2O
-------------------
Using eqn(4) to determine an expression for the non-water vapor
gases, we get,
pp(MOL) = WX . p(DryAir) ..................................(7)
MW(DryAir)
where WX = 0.001 . w(MOL) . ------------
MW(MOL)
and w(MOL) is still defined as in eqn(4).
This is based on the same methods used in the LBLRTM conversion code
in its lblatm.f module where molecular mixing ratios (either ppmv or
g/kg) are always with respect to DRY AIR.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 20-Sep-2002
paul.vandelst@ssec.wisc.edu
PP_TO_MR
NAME:
PP_to_MR
PURPOSE:
Function to convert gas concentrations from partial pressure in
hectoPascals to mass mixing ratio in g/kg.
CALLING SEQUENCE:
Mixing_Ratio = PP_to_MR( Pressure, & ! Input
Partial_Pressure, & ! Input
Molecule_ID=Molecule_ID, & ! Optional Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Partial_Pressure: Partial pressure of gas.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Molecule_ID: HITRAN molecular designation identifying the
molecule for which the concentration units
conversion is required. If not specified, the
default value is that for water vapor.
Valid values are:
1: H2O 9: SO2 17: HI 25: H2O2
2: CO2 10: NO2 18: ClO 26: C2H2
3: O3 11: NH3 19: OCS 27: C2H6
4: N2O 12: HNO3 20: H2CO 28: PH3
5: CO 13: OH 21: HOCl 29: COF2
6: CH4 14: HF 22: N2 30: SF6
7: O2 15: HCl 23: HCN 31: H2S
8: NO 16: HBr 24: CH3Cl 32: HCOOH
UNITS: N/A
TYPE: INTEGER
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Water_Vapor: Water vapor mass mixing ratio. If this argument is
not supplied, the mandatory PARTIAL_PRESSURE argument
is assumed to be water vapor.
This argument is ignored if the specified or default
molecule ID is set to 1.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Mixing_Ratio: Mass mixing ratio of gas. If an error occurs,
-1.0 is returned.
UNITS: g/kg
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
First a definition. In this routine, the mass mixing ratio of a gas
is defined to be, for a given volume, the ratio of the mass of the gas
in question to that of DRY air.
The ideal gas equation can be written as,
p = n.R0.T ................................................(1)
for unit volume, where
n = number of moles of gas,
R0 = universal gas constant
T = temperature.
The mass mixing ratio of a gas is defined as the mass of the gas with
respect to the mass of dry air in the same volume. If we use eqn(1)
to construct expressions for the partial pressures of a particular
gas and dry air, we get,
pp(MOL) = n(MOL).R0.T .................................(2a)
and
pp(DryAir) = n(DryAir).R0.T ..............................(2b)
Dividing eqn(2a) by (2b) and rearranging we get,
n(MOL)
pp(MOL) = ----------- . pp(DryAir) ........................(3)
n(DryAir)
Replacing the expssion for the number of moles of a substance into
eqn(3) gives us,
m(MOL) MW(DryAir)
pp(MOL) = --------- . ------------ . pp(DryAir)
MW(MOL) m(DryAir)
m(MOL) MW(DryAir)
= ----------- . ------------ . pp(DryAir)
m(DryAir) MW(MOL)
MW(DryAir)
= 0.001 . w(MOL) . ------------ . pp(DryAir) ......(4)
MW(MOL)
where m(MOL) = mass of gas MOL in grams,
m(DryAir) = mass of dry air in grams,
MW(MOL) = molecular weight of of gas MOL in grams,
MW(DryAir) = effective molecular weight of dry air in grams,
w(MOL) = mass mixing ratio of gas MOL in g/kg.
The factor of 0.001 in eqn(4) is to convert the units of the mixing
ratio from g/kg to g/g.
Thus to determine the mixing ratio of the gas in question from its
partial pressure, eqn(4) is rearranged to give,
MW(MOL) pp(MOL)
w(MOL) = 1000 . ------------ . ------------ ...............(5)
MW(DryAir) pp(DryAir)
Two cases need to be addressed:
-------------
1) MOL == H2O
-------------
If the gas for which the partial pressure is to be converted is water
vapor, then the dry air partial pressure required in eqn(5) is simply
computed using,
pp(DryAir) = p(Total) - pp(H2O)
which is then used in eqn(5) to compute the water vapour mixing ratio.
-------------------
2) MOL is *not* H2O
-------------------
For this gas, the dry air partial pressure must be computed using the
water vapor mixing ratio supplied in the optional Water_Vapor argument.
Eqn(4) above can be rewritten as,
pp(H2O) = WX . p(DryAir) ..................................(6)
MW(DryAir)
where WX = 0.001 . w(H2O) . ------------
MW(H2O)
Rearranging eqn(6), we then get,
pp(H2O)
p(DryAir) = --------- .....................................(7)
WX
But, eqn(6) can also be written as,
pp(H2O) = WX . ( p(Total) - pp(H2O) )
= ( WX . p(Total) ) - ( WX . pp(H2O) )
and thus,
pp(H2O) . ( 1 + WX ) = WX . p(Total)
with finally,
WX
pp(H2O) = ------------ . p(Total) .........................(8)
( 1 + WX )
Substituting eqn(8) into eqn(7) gives,
p(Total)
p(DryAir) = ---------- ....................................(9)
1 + WX
Eqn(9) is used to compute the dry air partial pressure which is then
used in enq(5) to compute the mixing ratio of the gas in question.
This is based on the same methods used in the LBLRTM conversion code
in its lblatm.f module where molecular mixing ratios (either ppmv or
g/kg) are always with respect to DRY AIR.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 20-Sep-2002
paul.vandelst@ssec.wisc.edu
PP_TO_MD
NAME:
PP_to_MD
PURPOSE:
Function to convert gas concentrations in pressure units to
mass density.
CALLING SEQUENCE:
Mass_Density = PP_to_MD( Pressure, & ! Input
Temperature, & ! Input
Molecule_ID=Molecule_ID, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total or partial pressure to provide number
density of air or specific gas species.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Molecule_ID: HITRAN molecular designation identifying the
molecule for which the concentration units
conversion is required. If not specified, the
default value is that for water vapor.
Valid values are:
1: H2O 9: SO2 17: HI 25: H2O2
2: CO2 10: NO2 18: ClO 26: C2H2
3: O3 11: NH3 19: OCS 27: C2H6
4: N2O 12: HNO3 20: H2CO 28: PH3
5: CO 13: OH 21: HOCl 29: COF2
6: CH4 14: HF 22: N2 30: SF6
7: O2 15: HCl 23: HCN 31: H2S
8: NO 16: HBr 24: CH3Cl 32: HCOOH
UNITS: N/A
TYPE: INTEGER
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Mass_Density: Number density of gas. If an error occurs,
-1.0 is returned.
UNITS: g/m^3
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
The ideal gas law is
p.V = n.R.T
where,
p = Pressure
V = volume
n = number of moles of the gas,
R = molar gas constant,
T = Temperature.
This can be written in terms of the number of molecules, N,
N
p.V = ---- . R.T ..............(1)
NA
where NA = Avogadro's constant (number of molecules in 1 mole.)
Eqn.(1) can be recast to provide the number of molecules in the
volume, the number density, nd,
N p.NA
nd = --- = ------ molecules/m^3 ..............(2)
V R.T
The mass density is related to the number density by the simple
relation,
MW
md = nd . ---- ..............(3)
NA
Substituting equation (2) into (3) gives,
p.MW
md = ------ g/m^3 ..............(4)
R.T
The value of p0 used in this routine is expressed in pascals (Pa) whereas
the input partial Pressure is expected to be hPa (more common unit). Thus
there is a factor of 100 to include,
100.p.MW
md = ---------- g/m^3
R.T
UNITS ANALYSIS:
p : kg.m^-1.s^-2 (Pascals)
MW : g.mol^-1
R : J.mol^-1.K^-1 == kg.m^2.s^-2.mol^-1.K^-1
T : K
kg g s^2.mol.K 1
md == ------- . ----- . ----------- . ---
m.s^2 mol kg.m^2 K
g
== -----
m^3
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 08-Nov-2004
paul.vandelst@ssec.wisc.edu
MD_TO_PP
NAME:
MD_to_PP
PURPOSE:
Function to convert gas concentration mass density to partial
pressure.
CALLING SEQUENCE:
Pressure = MD_to_PP( Mass_Density, & ! Input
Temperature, & ! Input
Molecule_ID=Molecule_ID, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Mass_Density: Number density of gas.
UNITS: g/m^3
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as Mass_Density
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Molecule_ID: HITRAN molecular designation identifying the
molecule for which the concentration units
conversion is required. If not specified, the
default value is that for water vapor.
Valid values are:
1: H2O 9: SO2 17: HI 25: H2O2
2: CO2 10: NO2 18: ClO 26: C2H2
3: O3 11: NH3 19: OCS 27: C2H6
4: N2O 12: HNO3 20: H2CO 28: PH3
5: CO 13: OH 21: HOCl 29: COF2
6: CH4 14: HF 22: N2 30: SF6
7: O2 15: HCl 23: HCN 31: H2S
8: NO 16: HBr 24: CH3Cl 32: HCOOH
UNITS: N/A
TYPE: INTEGER
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Pressure: Partial pressure for specified gas species.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as input Mass_Density
PROCEDURE:
The ideal gas law is
p.V = n.R.T
where,
p = Pressure
V = volume
n = number of moles of the gas,
R = molar gas constant,
T = Temperature.
This can be written in terms of the number of molecules, N,
N
p.V = ---- . R.T ..............(1)
NA
where NA = Avogadro's constant (number of molecules in 1 mole.)
Eqn.(1) can be recast to provide the number of molecules in the
volume, the number density, nd,
N p.NA
nd = --- = ------ molecules/m^3 ..............(2)
V R.T
The mass density is related to the number density by the simple
relation,
MW
md = nd . ---- ..............(3)
NA
Substituting equation (2) into (3) gives,
p.MW
md = ------ g/m^3 ..............(4)
R.T
and inverting equation (4) gives,
md.R.T
p = -------- Pa
MW
The pressure result above is determined in units of Pascals, so there
is a factor of 100 to include to return the pressure in units of
hectoPascals,
md.R.T
p = -------- hPa
100.MW
UNITS ANALYSIS:
md : g.m^-3
R : J.mol^-1.K^-1 == kg.m^2.s^-2.mol^-1.K^-1
T : K
MW : g.mol^-1
g kg.m^2 mol
p == ----- . ----------- . K . -----
m^3 s^2.mol.K g
kg
== -------
m.s^2
kg.m.s^-2 F
== ----------- == --- == pressure.
m^2 A
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 08-Nov-2004
paul.vandelst@ssec.wisc.edu
PP_TO_ND
NAME:
PP_to_ND
PURPOSE:
Function to convert gas concentrations in pressure units to
number density.
CALLING SEQUENCE:
Number_Density = PP_to_ND( Pressure, & ! Input
Temperature, & ! Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total or partial pressure to provide number
density of air or specific gas species.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Number_Density: Number density of gas. If an error occurs,
-1.0 is returned.
UNITS: molecules/m^3
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
The ideal gas law is
p.V = n.R.T
where,
p = Pressure
V = volume
n = number of moles of the gas,
R = molar gas constant,
T = Temperature.
This can be written in terms of the number of molecules, N,
N
p.V = ---- . R.T ..............(1)
NA
where NA = Avogadro's constant (number of molecules in 1 mole.)
Eqn.(1) can be recast to provide the number of molecules in the
volume, the number density, nd,
N p.NA
nd = --- = ------ molecules/m^3 ..............(2)
V R.T
At standard Temperature and Pressure (T0=273.15K, p0=101325Pa), this
number density is know as the Loschmidt constant, L0, the molecular
density of 1 mole of an ideal gas. Thus we have the generic form of
eqn.(2) and the STP form,
p0.NA
L0 = ------- molecules/m^3 ..............(3)
R.T0
Taking the ratio of eqns.(2) and (3) gives,
nd p.NA R.T0
-- = ------ . -------
L0 R.T p0.NA
and rearranging gives,
p T0
nd = L0 . ---- . ---- molecules/m^3
p0 T
The value of p0 used in this routine is expressed in pascals (Pa) whereas
the input partial Pressure is expected to be hPa (more common unit). Thus
there is a factor of 100 to include,
100.p T0
nd = L0 . ------- . ---- molecules/m^3
p0 T
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 15-Nov-2001
paul.vandelst@ssec.wisc.edu
ND_TO_PP
NAME:
ND_to_PP
PURPOSE:
Function to convert gas concentrations from number density to
pressure units.
CALLING SEQUENCE:
Partial_Pressure = ND_to_PP( Number_Density, & ! Input
Temperature, & ! Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Number_Density: Molecular density.
UNITS: molecules/m^3
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric Temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as Number_Density
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Partial_Pressure: Gas partial pressure. If an error occurs,
-1.0 is returned.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Same as input Number_Density
PROCEDURE:
The ideal gas law is
p.V = n.R.T
where,
p = Pressure
V = volume
n = number of moles of the gas,
R = molar gas constant,
T = Temperature.
This can be written in terms of the number of molecules, N,
N
p.V = ---- . R.T ..............(1)
NA
where NA = Avogadro's constant (number of molecules in 1 mole.)
Recasting eqn.(1) to provide the Pressure,
nd
p = ---- . R.T Pa ..............(2)
NA
where nd = the number density in molecules/m^3 = N/V.
At standard Temperature and Pressure (T0=273.15K, p0=101325Pa), the
number density of eqn.(2) is known as the Loschmidt constant, L0,
the molecular density of 1 mole of an ideal gas. Thus we have the
generic form of eqn.(2) and the STP form,
L0
p0 = ---- . R.T0 Pa ..............(3)
NA
Taking the ratio of eqns.(2) and (3) gives,
p nd T
---- = ---- . ---- Pa
p0 L0 T0
and rearranging gives,
nd T
p = p0 . ---- . ---- Pa
L0 T0
The value of p0 used in this routine is expressed in pascals (Pa) whereas
the output Pressure is returned as hPa (more common unit). Thus there
is a factor of 100 to include,
nd T
p = 0.01 . p0 . ---- . ---- hPa
L0 T0
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 15-Nov-2001
paul.vandelst@ssec.wisc.edu
PPMV_TO_ND
NAME:
PPMV_to_ND
PURPOSE:
Function to convert volume mixing ratio in ppmv to number density.
CALLING SEQUENCE:
Number_Density = PPMV_to_ND( Pressure, & ! Input
Temperature, & ! Input
ppmv, & ! Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
ppmv: Volume mixing ratio.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor number density. If this argument is
not supplied, the mandatory PPMV input argument
is assumed to be water vapor.
UNITS: molecules/m^3
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
Number_Density: Number density of gas. If an error occurs,
-1.0 is returned.
UNITS: molecules/m^3
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
To convert the volume mixing ratio of a molecular species, designated
by MOL, to number density, the following is used,
nd(MOL) = 1.0e-06 . ppmv(MOL) . ( nd(TOT) - nd(H2O) ) .....(1)
where
Pressure T0
nd(TOT) = L0 . ---------- . ------------- molecules/m^3
p0 Temperature
and L0 = Loschmidt number,
p0 = Standard pressure,
T0 = Standard temperature.
If the input molecule is water vapor, the number density is
determined using,
ppmv(H2O) . 1.0e-06
nd(H2O) = ----------------------------- . nd(TOT) .....(2)
1 + ( ppmv(H2O) . 1.0e-06 )
Rearranging eqn.(2) gives the same form as eqn.(1).
This is based on the same methods used in the LBLRTM conversion code
in its lblatm.f module where molecular mixing ratios (either ppmv or
g/kg) are always with respect to DRY AIR.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 15-Nov-2001
paul.vandelst@ssec.wisc.edu
ND_TO_PPMV
NAME:
ND_to_PPMV
PURPOSE:
Function to convert gas concentrations from number density to volume
mixing ratio in ppmv.
CALLING SEQUENCE:
ppmv = ND_to_PPMV( Pressure, & ! Input
Temperature, & ! Input
Number_Density, & ! Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Total atmospheric pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Atmospheric temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Number_Density: Molecular number density.
UNITS: molecules/m^3
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor volume mixing ratio. If this argument is
not supplied, the mandatory NUMBER_DENSITY input
argument is assumed to be water vapor.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
ppmv: Gas volume mixing ratio. If an error occurs,
-1.0 is returned.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
To convert the number density of a molecular species, designated
by MOL, to volume mixing ratio, the following is used,
nd(MOL)
ppmv(MOL) = 1.0e+06 . -------------
nd(DRY_AIR)
where
nd(DRY_AIR) = nd(TOT) - nd(H2O)
and
Pressure T0
nd(TOT) = L0 . ---------- . ------------- molecules/m^3
p0 Temperature
with L0 = Loschmidt number,
p0 = Standard pressure,
T0 = Standard temperature, and
If the input molecule is NOT water vapor, the dry air number density
is determined using,
1
nd(DRY_AIR) = ----------------------------- . nd(TOT)
1 + ( ppmv(H2O) . 1.0e-06 )
This is based on the same methods used in the LBLRTM conversion code
in its lblatm.f module where molecular mixing ratios (either ppmv or
g/kg) are always with respect to DRY AIR.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 15-Nov-2001
paul.vandelst@ssec.wisc.edu
PPMV_TO_KMOL
NAME:
PPMV_to_KMOL
PURPOSE:
Function to convert layer gas concentrations from volume mixing ratio
in ppmv to column density in kmol.cm^-2.
CALLING SEQUENCE:
kmol_per_cm2 = PPMV_to_KMOL( Pressure, & ! Input
Temperature, & ! Input
Delta_Z, & ! Input
ppmv, & ! Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Average layer pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Average layer temperature
UNITS: Kelvin, K (K)
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Delta_Z: Layer thickness
UNITS: metres, m
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
ppmv: Average layer gas concentration
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor column density. If this argument is
not supplied, the mandatory PPMV input
argument is assumed to be water vapor.
UNITS: kmol.cm^-2
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
kmol_per_cm2: Layer gas concentration. If an error occurs,
-1.0 is returned.
UNITS: kmol.cm^-2
TYPE: REAL(fp)
DIMENSION: Same input Pressure
PROCEDURE:
The column density of a particular molecular species, designated
by MOL, given its volume mixing ratio is then given by,
cd(MOL) = 1.0e-06 . ppmv(MOL) . cd(DRY_AIR) kmol.cm^-2
First, the total number density is calculated using,
p T0
nd(TOT) = L0 . ---- . ---- molecules.m^-3
p0 T
and L0 = Loschmidt number,
p0 = Standard pressure,
T0 = Standard temperature.
The total column density is calculated by multiplying the number
density by the layer thickness in metres, dz,
cd(TOT) = dz . nd(TOT) molecules.m^-2
This result is scaled by:
a) 10^-4 to convert molecules.m^-2 to molecules.cm^-2
b) 1/Na to convert molecules.cm^-2 to mol.cm^-2, and
c) 10^-3 to convert mol.cm^-2 to kmol.cm^-2
giving,
1.0e-07
cd(TOT) = --------- . dz . nd(TOT) kmol.cm^-2
Na
The dry air column density is then calculated using,
1
cd(DRY_AIR) = ----------------------------- . cd(TOT) kmol.cm^-2
1 + ( ppmv(H2O) . 1.0e-06 )
for water vapor ppmv input or,
cd(DRY_AIR) = cd(TOT) - cd(H2O)
if cd(H2O) is supplied via the optional Water_Vapor argument.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 04-Jan-2001
paul.vandelst@ssec.wisc.edu
KMOL_TO_PPMV
NAME:
KMOL_to_PPMV
PURPOSE:
Function to convert layer gas concentrations from column density in
kmol.cm^-2 to volume mixing ratio in ppmv.
CALLING SEQUENCE:
ppmv = KMOL_to_PPMV( Pressure, & ! Input
Temperature, & ! Input
Delta_Z, & ! Input
kmol_per_cm2, & ! Input
Water_Vapor=Water_Vapor, & ! Optional Input
Message_Log=Message_Log ) ! Error messaging
INPUT ARGUMENTS:
Pressure: Average layer pressure.
UNITS: hectoPascals, hPa
TYPE: REAL(fp)
DIMENSION: Scalar or Rank-1 (K x 1)
ATTRIBUTES: INTENT(IN)
Temperature: Average layer temperature
UNITS: Kelvin, K
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
Delta_Z: Layer thickness
UNITS: metres, m
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
kmol_per_cm2: Column density for molecular species.
UNITS: kmol.cm^-2
TYPE: REAL(fp)
DIMENSION: Same as Pressure
ATTRIBUTES: INTENT(IN)
OPTIONAL INPUT ARGUMENTS:
Water_Vapor: Water vapor volume mixing ratio. If this argument
is not supplied, the mandatory KMOL_PER_CM2 input
argument is assumed to be water vapor.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as pressure
ATTRIBUTES: OPTIONAL, INTENT(IN)
Message_Log: Character string specifying a filename in which any
Messages will be logged. If not specified, or if an
error occurs opening the log file, the default action
is to output Messages to standard output.
UNITS: N/A
TYPE: CHARACTER(*)
DIMENSION: Scalar
ATTRIBUTES: OPTIONAL, INTENT(IN)
FUNCTION RESULT:
ppmv: Layer gas volume mixing ratio. If an error occurs,
-1.0 is returned.
UNITS: ppmv
TYPE: REAL(fp)
DIMENSION: Same as input Pressure
PROCEDURE:
The volume mixing ratio of a particular molecular species, designated
by MOL, given it's column density is given by,
cd(MOL)
ppmv(MOL) = 1.0e-06 . -------------
cd(DRY_AIR)
First, the total number density is calculated using,
p T0
nd(TOT) = L0 . ---- . ---- molecules.m^-3
p0 T
and L0 = Loschmidt number,
p0 = Standard pressure,
T0 = Standard temperature.
The total column density is calculated by multiplying the number
density by the layer thickness in metres, dz,
cd(TOT) = dz . nd(TOT) molecules.m^-2
This result is scaled by:
a) 10^-4 to convert molecules.m^-2 to molecules.cm^-2
b) 1/Na to convert molecules.cm^-2 to mol.cm^-2, and
c) 10^-3 to convert mol.cm^-2 to kmol.cm^-2
giving,
1.0e-07
cd(TOT) = --------- . dz . nd(TOT) kmol.cm^-2
Na
The dry air column density is then calculated using,
1
cd(DRY_AIR) = ----------------------------- . cd(TOT) kmol.cm^-2
1 + ( ppmv(H2O) . 1.0e-06 )
for water vapor ppmv input or,
cd(DRY_AIR) = cd(TOT) - cd(H2O)
if cd(H2O) is supplied via the optional Water_Vapor argument.
CREATION HISTORY:
Written by: Paul van Delst, CIMSS/SSEC 04-Jan-2001
paul.vandelst@ssec.wisc.edu