Bias correction method applied within ISI-MIP, friendly reminder for ISI-MIP Analysis workshop

Posted on Aug. 31, 2012

1) Since the official release of the ISI-MIP data we have put a lot of effort into testing and documenting the bias correction method. We have found that the algorithm currently used does not do exactly what we want: In some cases, due to a technical problem, the width of the frequency distribution of daily data is not corrected. That means that in these cases, the variability on the daily timescale is closer to the original GCM data. The problem is related to the precipitation data and to a minor extent to the other variables that are corrected in a multiplicative way. Temperature data are not affected.

The problem does not affect the correction of the monthly means, and the input data that is currently being used still represents plausible climate scenarios. The current ISI-MIP data set will remain valid.

We have corrected for the error and included some improvements in the code. Once we have finished testing and documenting this improved version, we will provide you with relevant plots and details in order to compare the results of both versions; however, we wanted to share our findings with you already now, so that you are aware of the shortcomings of the method that is currently used. The technical problem, its implications and the corrected method will be described in a paper we are currently working on. It should become the reference for the ISI-MIP data. We will also provide the updated data. They can be used for a sensitivity analysis but will not replace the current ISI-MIP data set that will stay the reference set for the intercomparisons.

2) To those who are attending the workshop in Reading next week, we would like to encourage you once more to bring with you any plots, data tables or other material, even very preliminary, that might potentially be useful for the discussions. Looking forward to meeting you there!