[NARCCAP-discuss] Model evaluation and bias correction

Michael Wehner mfwehner at lbl.gov
Mon Jun 13 10:51:27 MDT 2011


Shuang-Ye
You raise a number of difficult questions.

1) is it appropriate to compare models directly with station data? Or should one compare to a gridded observational product? I am using the the data at http://www.esrl.noaa.gov/psd/data/gridded/data.unified.html
2) How does one evaluate different models in a multi-model context? See http://www.ipcc-wg2.gov/meetings/EMs/IPCC_EM_MME_GoodPracticeGuidancePaper.pdf for some useful perspectives.
3)  NCEP vs GCM runs for bias corrections. I don't think that there is a correct answer for this question. Given that there is only a single realization for each RCM, there is no way to access the statistical significance of the differences in bias corrections obtained by using the differently driven runs. For consistency in the projections, one might argue that you should use the GCM driven runs. On the other hand, it would also make sense to use both to make a small attempt to determine robustness. 

Hope that this helps.
Michael

On Jun 13, 2011, at 9:24 AM, Shuang-Ye Wu wrote:

> Hi all,
> 
> This question might be a bit lengthy, so please bear with me.
> 
> I am trying to use NARCCAP models to project possible changes in daily
> precipitation pattern for a particular area.  The first step is to compare
> NARCCAP model retrospective runs with observed station data.  The next step
> is to correct bias based on this comparison, using some kind of scaling
> methods.  My question is: should I use NCEP-driven runs or GCM-driven runs
> for the comparison and bias correction?  I thought I should use GCM-driven
> retropsective runs to evaluate the total bias from both the global and
> regional models, and correct the total bias for future projections.  But
> some suggest I should use NCEP runs for model evaluation, because I'd then
> compare observation with NARCCAP models driven by observation data.  If
> that's the case, should I do bias correction separately using GCM-driven
> runs?  Any ideas/suggestions?
> 
> Thank you!
> 
> Best,
> Shuang-Ye
> 
> -- 
> 
> 
> 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Shuang-Ye Wu, PhD
> Assistant Professor
> Geology Department
> University of Dayton
> 300 College Park
> Dayton, Ohio 45469-2364
> Tel: 937-229-1720
> Fax: 937-229-2889
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