Difference between revisions of "Physical constants"

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Placeholder for information about physical constants used in GEOS-Chem.
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== Overview ==
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<span style="color:green">'''''This update was validated with [[GEOS-Chem_v11-01_benchmark_history#v11-01f|1-month benchmark simulation v11-01f]] and [[GEOS-Chem_v11-01_benchmark_history#v11-01f-geosfp-Run0|1-year benchmark simulation v11-01f-geosfp-Run0]]. This version was approved on 16 Apr 2016.'''''</span>
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In v11-01f, we made the following changes:
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*Changed the name of the global physical parameter file from <tt>/Headers/CMN_GCTM_mod.F</tt> to <tt>/Headers/physconstants.F</tt>
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*Updated all files in <tt>GeosCore</tt> to use physical parameters in <tt>/Headers/physconstants.F</tt>
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*Added Boltzmann's constant and standard atmosphere to global physical parameters available
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*Adjusted hard-coded physical parameter values in HEMCO to match global physical parameter values
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*Adjusted molar gas constant value in <tt>/GeosUtil/henry_mod.F</tt> to match value in <tt>/Headers/physconstants.F</tt>
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*Adjusted values of some global physical parameters to match [http://physics.nist.gov/cuu/Constants/bibliography.html NIST, 2014] values
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Prior and updated values of global physical constants in <tt>/Headers/physconstants.F</tt> are listed in the table below. All values use flexible precision and are therefore double-precision unless compiling with single-precision enabled. Parameters in v11-01f that are different than in previous versions, either due to different values or because they were previously not included, are in bold.
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{| border=1 cellspacing=0 cellpadding=5
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|-bgcolor="#CCCCCC"
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!width="300px"|Parameter
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!width="150px"|Description
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!width="150px"|Units
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!width="150px"|Prior to v11-01f
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!width="150px"|v11-01f
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!width="200px"|Source
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|-valign="top"
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|Avogadro's Number
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|AVO
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|particles/mol
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|6.022e+23
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|'''6.022140857e+23'''
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|NIST, 2014
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|-valign="top"
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|Acceleration due to gravity at earth's surface
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|g0
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|m/s<sup>2</sup>
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|9.8
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|'''9.80665'''
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|NIST, 2014
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|-valign="top"
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|Pi
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|PI
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|unitless
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|3.14159265358979323
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|3.14159265358979323
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|legacy
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|-valign="top"
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|Molar gas constant
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|RSTARG
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|J/K/mol
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|8.31450
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|'''8.3144598'''
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|NIST, 2014
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|-valign="top"
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|Standard atmosphere
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|ATM
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|Pa
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|Not Included
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|'''101325'''
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|NIST, 2014
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|-valign="top"
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|Boltzmann's constant
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|BOLTZ
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|J/K
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|Not Included
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|'''1.38064852e-23'''
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|NIST, 2014
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|-valign="top"
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|Von Karman's constant
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|VON_KARMAN
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|Unitless
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|0.4
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|0.4
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|legacy
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|-valign="top"
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|Radius of earth
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|Re
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|m
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|6.375e+6
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|6.375e+6
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|legacy
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|-valign="top"
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|Dry air gas constant
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|Rd
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|J/K/kg
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|287.0
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|287.0
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|legacy
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|-valign="top"
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|Water vapor gas constant
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|Rv
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|J/K/kg
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|Not Included
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|'''461.0'''
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|legacy
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|-valign="top"
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|Molecular weight of dry air
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|AIRMW
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|g/mol
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|28.97
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|28.97
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|legacy
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|-valign="top"
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|Molecular weight of water
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|H2OMW
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|g/mol
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|18.016
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|18.016
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|legacy
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|-valign="top"
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|Scale height of the atmosphere
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|SCALE_HEIGHT
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|m
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|7600
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|7600
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|legacy
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|-valign="top"
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|Molecules dry air per kg dry air
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|XNUMOLAIR
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|molecules/kg
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|AVO / 28.9644e-3
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|'''AVO / ( AIRMW * 1e-3 )'''
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|N/A
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|-valign="top"
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|100 divided by acceleration due to gravity
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|g0_100
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|s<sup>2</sup>/m
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|100. / g0
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|100. / g0
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|legacy
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|-valign="top"
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|Pi divided by 180
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|PI_180
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|unitless
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|PI / 180.
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|PI / 180.
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|legacy
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|-valign="top"
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|Dry air gas constant divided by the acceleration due to gravity
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|Rdg0
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|J s<sup>2</sup>/K/kg/m
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|Rd / g0
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|Rd / g0
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|legacy
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|}
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'''Important Notes:'''
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*Physical parameters are still hard-coded in several places within HEMCO. Using a single set of global physical parameters in HEMCO will be in a future HEMCO version update.
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*Values for pi and the radius of the earth are also defined in <tt>/GeosUtil/regrid_a2a_mod.F90</tt> and values for the molar gas constant and standard atmosphere are also defined in <tt>/GeosUtil/henry_mod.F</tt>. These definitions remain so that the HEMCO standalone software has access to them. In the current version of HEMCO, the HEMCO standalone does not download <tt>/Headers/physconstants.F</tt> and therefore does not have access to global parameters defined in that file. This design may change in a future version.
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--[[User:Lizzie Lundgren|Lizzie Lundgren]] ([[User talk:Lizzie Lundgren|talk]]) 20:44, 12 January 2016 (UTC)<br>--[[User:Bmy|Bob Yantosca]] ([[User talk:Bmy|talk]]) 15:34, 30 March 2016 (UTC)

Latest revision as of 20:12, 13 July 2023

Overview

This update was validated with 1-month benchmark simulation v11-01f and 1-year benchmark simulation v11-01f-geosfp-Run0. This version was approved on 16 Apr 2016.

In v11-01f, we made the following changes:

  • Changed the name of the global physical parameter file from /Headers/CMN_GCTM_mod.F to /Headers/physconstants.F
  • Updated all files in GeosCore to use physical parameters in /Headers/physconstants.F
  • Added Boltzmann's constant and standard atmosphere to global physical parameters available
  • Adjusted hard-coded physical parameter values in HEMCO to match global physical parameter values
  • Adjusted molar gas constant value in /GeosUtil/henry_mod.F to match value in /Headers/physconstants.F
  • Adjusted values of some global physical parameters to match NIST, 2014 values

Prior and updated values of global physical constants in /Headers/physconstants.F are listed in the table below. All values use flexible precision and are therefore double-precision unless compiling with single-precision enabled. Parameters in v11-01f that are different than in previous versions, either due to different values or because they were previously not included, are in bold.

Parameter Description Units Prior to v11-01f v11-01f Source
Avogadro's Number AVO particles/mol 6.022e+23 6.022140857e+23 NIST, 2014
Acceleration due to gravity at earth's surface g0 m/s2 9.8 9.80665 NIST, 2014
Pi PI unitless 3.14159265358979323 3.14159265358979323 legacy
Molar gas constant RSTARG J/K/mol 8.31450 8.3144598 NIST, 2014
Standard atmosphere ATM Pa Not Included 101325 NIST, 2014
Boltzmann's constant BOLTZ J/K Not Included 1.38064852e-23 NIST, 2014
Von Karman's constant VON_KARMAN Unitless 0.4 0.4 legacy
Radius of earth Re m 6.375e+6 6.375e+6 legacy
Dry air gas constant Rd J/K/kg 287.0 287.0 legacy
Water vapor gas constant Rv J/K/kg Not Included 461.0 legacy
Molecular weight of dry air AIRMW g/mol 28.97 28.97 legacy
Molecular weight of water H2OMW g/mol 18.016 18.016 legacy
Scale height of the atmosphere SCALE_HEIGHT m 7600 7600 legacy
Molecules dry air per kg dry air XNUMOLAIR molecules/kg AVO / 28.9644e-3 AVO / ( AIRMW * 1e-3 ) N/A
100 divided by acceleration due to gravity g0_100 s2/m 100. / g0 100. / g0 legacy
Pi divided by 180 PI_180 unitless PI / 180. PI / 180. legacy
Dry air gas constant divided by the acceleration due to gravity Rdg0 J s2/K/kg/m Rd / g0 Rd / g0 legacy

Important Notes:

  • Physical parameters are still hard-coded in several places within HEMCO. Using a single set of global physical parameters in HEMCO will be in a future HEMCO version update.
  • Values for pi and the radius of the earth are also defined in /GeosUtil/regrid_a2a_mod.F90 and values for the molar gas constant and standard atmosphere are also defined in /GeosUtil/henry_mod.F. These definitions remain so that the HEMCO standalone software has access to them. In the current version of HEMCO, the HEMCO standalone does not download /Headers/physconstants.F and therefore does not have access to global parameters defined in that file. This design may change in a future version.

--Lizzie Lundgren (talk) 20:44, 12 January 2016 (UTC)
--Bob Yantosca (talk) 15:34, 30 March 2016 (UTC)

Retrieved from "https://wiki.seas.harvard.edu/geos-chem/index.php?title=Physical_constants&oldid=52506"