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A posteriori adjustment of near‐term climate predictions: Accounting for the drift dependence on the initial conditions
Author(s) -
Fučkar Neven S.,
Volpi Danila,
Guemas Virginie,
DoblasReyes Francisco J.
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl060815
Subject(s) - northern hemisphere , a priori and a posteriori , climatology , proxy (statistics) , term (time) , environmental science , regression , linear regression , scale (ratio) , climate model , econometrics , climate change , statistics , mathematics , geology , physics , philosophy , oceanography , epistemology , quantum mechanics
Climate predictions initialized from an observationally based state (OBS) drift toward the state of the unconstrained model, which makes the use of a posteriori correction methods essential to disentangle the climate signal of interest from the model bias. We propose that applying a linear regression of the predictions and corresponding OBS on the OBS initial conditions (IC), and substituting the latter for the former, offers an effective method for bias correction. The impact of this new method is examined on monthly means of large‐scale sea surface temperature indices and the Northern Hemisphere sea ice extent in EC‐Earth2.3 predictions. This postprocessing adjustment through a linear regression on the averaged OBS over the first forecast month as a temporarily smoothed proxy for OBS IC shows a reduction of model error with respect to the two established bias correction methods. Improvements are seen for at least two seasons and for some variables up to 5 years.