ACCESS-ESM Last Interglacial
The configuration parameters for the Last Interglacial (LIG) should follow the experiment setup in LIG Design.
The configuration for the Last Interglacial Model of ACCESS-ESM is based on the payu version of ACCESS-ESM piControl, and can be found on GitHub:coecms/esm-lig
Differences between piControl and LIG
The differences between piControl and LIG fall in two categories:
Some concentrations are different between piControl and LIG:
These values are set in the payu control directory, under Template:Atmosphere/namelists, with the variable names CO2_MMR, CH4MMR, and N2OMMR, respectively. Since ACCESS-ESM expects these values to be in Mass-Mixing Ratio, the desired values have to be converted from ppm/ppb to MMR.
The path of earth around the sun has changed since the last interglacial, so changes have to be accommodated.
|Date of vernal equinox||March 21 at noon||March 21 at noon|
|Time of parahelion passage in days||2.667||170.9046|
These specifications are hardcoded in the UM (at least in version 7.3 which we are using for ACCESS-ESM) in the header file include/constant/astron.h.
! ! Eccentricity of the orbit Real, Parameter :: E_DFLT = 1.6710222E-02 ! ! ! Longitude of the perihelion in radians Real, Parameter :: LPH_DFLT = 102.94719*PI/180.0 ! ! ! Obliquity of the orbit - corresponds to 23.43929111 degrees Real, Parameter :: OBLQ_DFLT = 0.409092804 ! ! ! Reference year for setting the date of the vernal equinox Integer, Parameter :: YEAR_REF_VE = 2000 ! ! ! Date of the vernal equinox in days after the start of the year ! ! This date is for the year 2000. Real, Parameter :: DATE_VE_DFLT = 79.3159 ! ! The final parameter required is the time of the perihelion ! passage, TAU0. For a pure Keplerian orbit, with a specified ! eccentricity and longitude of the perihelion, this can be ! deduced from the date of the vernal equinox (as is specified ! in AMIP-2, for example). In practice it is somewhat more ! complicated to calculate the time of the perihelion. ! For simplicity, a mean value for the years 1995-2005 is used ! here: note that the range of TAU0 in this period is from ! 1.0 to 3.75 and that there is no simple relationship with leap ! years. ! ! ! Time of the perihelion passage in days Real, Parameter :: TAU0_DFLT = 2.667
The values were changed to the new values, checked into the repository at https://access-svn.nci.org.au/svn/cmip5/branches/dev/hxw599/pmip, and compiled into the executable /short/public/access-esm/payu/bin/coe/um_hg3.exe-20190412-pmip-r327 (where the r327 stands for the revision number in the subversion repository).