Calendars

LMDZ can run using various calendars.

The choice of calendar is set using the calend parameter (string) in the run.def file, which may be set to:

• calend=earth_360d (default value if calend is not set) : years of 360 days (12 months of 30 days each)
• calend=earth_365d : years of 365 days (12 months of varying length; 28 days in February every year)
• calend=earth_366d : real gregorian year of 365 or 366 days with leap years
• calend=gregorian : same as earth_366d

The default behavior of the model is to use the date read in the start.nc file as an initial date for the run (and thus technically continue time marching where it had left off at the previous simulation). But the user may reset the date via the following flag:

• raz_date=1 (default is 0, i.e. no calendar reset, continue from date read in the start file) : reset the calendar

If resetting the calendar then the user should also provide in run.def :

• anneeref=... : calendar year (default=1998; why not? have to start somewhere...)
• dayref=... : day of the year at which the simulation starts (default=1; i.e. first day of the year)
• starttime=... : hour at which the simulation begins (default=0 ; i.e. midnight at longitude 0)

03/12/2021