ISIMIP2: Flux variables on 360_day calendar for monthly and annual data #30


Matthias Büchner reported on Dec. 8, 2022.
We became aware of a potential problem with using the 360_day calendar we requested for monthly and annual data. Most models resolve the days of the year internally, using the 365-day or proleptic_gregorian calendar, just like the input data, meaning they account for the length of the months according to a real calendar. This can be problematic when aggregating monthly given fluxes in s-1 or d-1 from the output data. NetCDF tools and APIs would then assume that each month has 30 days and thus miscalculate aggregations for months with a different length in the model simulation.

Before analyzing flux variables from ISIMIP2 please lookup the calendar attribute of daily outputs from the same model and apply the number of days per month accordingly.

As far as we know, in ISIMIP2a only the fire sector and two models from the global water sector are affected, namely WaterGAP2-2c and WEB-DHM-SG. In ISIMIP2b, we are now aware of the VIC and JULES-ES-55 models, but it is likely that more models are affected.


Affected datasets can still be used for simulations or research.

Severity low

Status won't fix

before 20221208
Data product
Output Data, Secondary Output Data
admeluse, adomuse, adomww, ainduse, aindww, airruse, airrusegreen, airrww, aliveuse, aliveww, amanuse, amanww, arainfusegreen, atotuse, dis, ecoatmflux, esoil, evap, fireint, gpp, intercep, nee, npp, nppabovegroundwood, nppagwood, nppbelowgroundwood, nppbgwood, npplandleaf, npplandroot, nppleaf, npproot, pdomuse, pirruse, pirrusegreen, pirrww, pmanuse, potevap, ptotuse, ptotww, qbaseflow, qg, qr, qrecharge, qs, qsb, qtot, ra, rh, rr, trans, turbdiffheat
Time step
annual, monthly
Simulation round

Affected datasets

There are 49303 datasets affected by this issue. Here we only display the first 100 datasets. You can download a complete list of all the datasets, or files affected by this issue as JSON. Alternatively, can also download a list the files as a flat file suitable for Wget. You can use the search interface to further restrict your query.