[Proflist] JCSDA Seminar, Today, 2 PM: Craig Bishop

[George Ohring]

* *****

*JCSDA Seminar*****

*Title*****

*Hidden Error Variance Theory and its use in Hybrid Data Assimilation***

*Speaker*****

*Craig Bishop
Naval Research Laboratory ***

*Date,  Time & Place*****

*Friday,  November 2, 2012
**2:00 – 3:00 PM, Conference Center*, NOAA Center for Weather and Climate
Prediction, 5830 University Research Court, College Park, MD ****

*Abstract*****

A conundrum of predictability research is that while the prediction of flow
dependent error distributions is one of its main foci, chaos fundamentally
hides flow dependent forecast error distributions from empirical
observation. Empirical estimation of such error distributions requires that
one obtain a large sample of error realizations given the same flow and the
same observational network.  However, chaotic elements of the flow and the
observing network make it practically impossible to observe and collect the
conditioned sample of errors required to empirically define such
distributions and their variance. These variances are “hidden”. Here, an
exposition of the problem is developed from an ensemble Kalman filter data
assimilation system applied to a 10 variable non-linear chaotic model and
25,000 replicate models. The output from this system motivates a new
analytical model for the distribution of true error variances given an
imperfect ensemble variance. This model is defined by 6 parameters that
also determine the optimal weights for the static and flow dependent parts
of Hybrid error variance models.  Six new equations enable these hidden
parameters to be accurately estimated from a long time series of
(innovation, ensemble variance) data pairs.  This new-found ability to
estimate hidden parameters provides new tools for assessing the quality of
ensemble forecasts, tuning Hybrid error variance models and for
post-processing ensemble forecasts. Preliminary results from attempts to
use the theory to speed the tuning of Hybrid data assimilation schemes will
also be presented.****

*Remote Access*****

*Video:* 1. Go to JCSDA Seminar <https://star-nesdis-noaa.webex.com/> and
click on the seminar title
2. Enter your name and email address.
3. Enter the meeting password: JCSDAseminars707
4. Click "Join Now".
5. Follow the instructions that appear on your screen.
*Audio: *USA participants: 1-866-715-2479,  Passcode: 9457557
International:                    1-517-345-5260****

*Contact*****

If you would like to present a seminar contact George.Ohring at noaa.gov****
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