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

Jochen Klar opened this caveat 9 months ago.

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Title
Discontinuities found in ISIMIP3b bias-adjusted climate input data
Description
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/
Severity
medium
Status
resolved
Versions
before 20210101
Region
Global simulation
Data product
Input Data
Input category
Climate forcing
Input subcategory
Atmosphere
Bias adjustment
w5e5
Climate forcing
GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2-HR, MRI-ESM2-0, UKESM1-0-LL
Climate scenario
historical, picontrol, ssp126, ssp370, ssp585
Climate variable
hurs, huss, pr, prsn, ps, rlds, rsds, sfcwind, tas, tasmax, tasmin
Simulation round
ISIMIP3b simulation round

Figures

Discontinuities found in bias-adjusted climate input data (all land)
Discontinuities found in bias-adjusted climate input data (ocean)

Comments

Matthias Büchner commented 8 months ago.
Updates are expected to become available in May 2021. Stay tuned.
Matthias Büchner commented 6 months, 4 weeks ago.
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/
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Affected datasets