Last millennium prescribed values give a spectral solar irradiance (SSI), which is a function of time and wavelength. ACCESS-ESM uses a simplified radiation model which takes in the total solar irradiance (TSI).
TSI has been calculated as the integral of SSI over wavelength (using the SSI and bin width values from the prescribed file) + 4.9 w/m2. The constant is added following the procedure of the ACCESS-ESM CMIP6 runs which add 4.9 w/m2 to the prescribed TSI to allow runs to be initialised from their piControl run, which used CMIP5 TSI values (see Ziehn et. al.).
The original ESM source code allows TSI to be given from 1700 to 2300. Code modifications have been made to the UM to allow it to read the longer time series given here.
Last millennium prescribed values give a spectral solar irradiance (SSI), which is a function of time and wavelength. ACCESS-ESM uses a simplified radiation model which takes in the total solar irradiance (TSI).
TSI has been calculated as the integral of SSI over wavelength (using the SSI and bin width values from the prescribed file) + 4.9 w/m2. The constant is added following the procedure of the ACCESS-ESM CMIP6 runs which add 4.9 w/m2 to the prescribed TSI to allow runs to be initialised from their piControl run, which used CMIP5 TSI values (see Ziehn et. al.).
The original ESM source code allows TSI to be given from 1700 to 2300. Code modifications have been made to the UM to allow it to read the longer time series given here.