7 Warming Air Scenario

A common application using GLM is to undertake scenarios to assess how conditions might change in a warmer world. For example, how would stratification and water quality concentrations change if the air temperature increased by 2 °C?

This can be achieved by altering the boundary condition files, such as the meteorology and inflow files, to represent this type of climate change scenario.

Check whether your simulation package has a pre-made version of the meteorology file in the bcs folder, with the air temperature increased by 2 °C. For example, the file may be called met_1997_2004_airT2.csv. To use this file, update meteo_fl = 'bcs/met_1997_2004.csv' in the &meteorology section of glm3.nml.

Or alternatively you can edit the met_hourly.csv file to reflect these conditions. Open the met file in Excel and alter the conditions (e.g. add 2C to the air temperature) and then re-save the file as a new met csv file. Make sure to save with correct date format, taking note these met measurements are recorded hourly, so use the format YYYY-MM-DD hh:mm.

!-------------------------------------------------------------------------------
! meteorology
!-------------------------------------------------------------------------------
&meteorology
   met_sw      = .true.
   lw_type     = 'LW_IN'
   rain_sw     = .false.
   atm_stab    = 0
   fetch_mode  = 0
  !rad_mode    = 1
   albedo_mode = 1
   cloud_mode  = 4
 !-- BC file details
   subdaily    = .true.
   meteo_fl    = 'bcs/met_1997_2004.csv'   !<---- UPDATE THIS LINE TO READ THE NEW FILE
   wind_factor = 0.9
   lw_factor   = 1.0
   lw_offset   = 0.0
 !-- Parameters
   ce = 0.0013
   ch = 0.0013
   cd = 0.0013
/

Once you have successfully updated the GLM configuration to use the new air temperature boundary condition, examine the surface water temperature and phytoplankton outputs and compare them to the baseline scenario. This can be done by creating a time-series plot comparing the two simulations, and computing the mean difference between the two.