Discontinuities found in ISIMIP3b bias-adjusted climate input data #1

issue

Jochen Klar reported on March 2, 2021.
Statistics of ISIMIP3b bias-adjusted climate input data were found to be discontinuous at each turn of the month. The reason for this is that the ISIMIP3 bias adjustment was applied calendar month by calendar month.

In short, all values belonging to a particular month were pooled and then quantile-mapped such that the distribution of those pooled values became more similar to the observed distribution. Where simulated and observed annual cycles differ in shape, this approach produced discontinuous annual cycles.

The discontinuities potentially occur at every turn of the month for all climate variables and statistics.

As an example, see the downloads or the figure below. There we show the 2001-2010 multi-year daily mean values of several climate variables averaged over all land (left-side figure) or ocean (right-side figure) grid cells, with results before and after bias adjustment shown in the left and right column, respectively.

Additional plots valid for regions after Giorgi and Bi (2005) are available under these links:
annual cycles: https://www.isimip.org/files/plots/inputdata/ISIMIP3BASDv2.4.1/annual_cycle/png_united/
annual means: https://www.isimip.org/files/plots/inputdata/ISIMIP3BASDv2.4.1/annual_means/png_united/
Discontinuities found in bias-adjusted climate input data (all land)
Discontinuities found in bias-adjusted climate input data (all land)
Discontinuities found in bias-adjusted climate input data (ocean)
Discontinuities found in bias-adjusted climate input data (ocean)
Matthias Büchner commented on May 7, 2021.
First plots of two climate input models bias-adjusted with the new ISIMIP3BASD version 2.5.0 look promising. The plots linked below suggest that our approach for fixing the discontinuities is working as expected.
annual cycles: https://www.isimip.org/files/plots/inputdata/ISIMIP3BASDv2.5.0/annual_cycle/png_united/
annual means: https://www.isimip.org/files/plots/inputdata/ISIMIP3BASDv2.5.0/annual_means/png_united/
Matthias Büchner commented on March 31, 2021.
Updates are expected to become available in May 2021. Stay tuned.

Details

Please use the replaced datasets for new simulations or research.

Severity high

Status resolved

Versions
before 20210101
Region
Global
Data product
Input Data
Input category
Climate related forcing
Input subcategory
Atmospheric forcings
Bias adjustment
w5e5
Climate forcing
GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2-HR, MRI-ESM2-0, UKESM1-0-LL
Climate experiment
historical, picontrol, ssp126, ssp370, ssp585
Climate variable
hurs, huss, pr, prsn, ps, rlds, rsds, sfcwind, tas, tasmax, tasmin
Simulation round
ISIMIP3b

Downloads

Affected datasets

There are 275 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.