[Proflist] Today, 2 PM, Joint Center for Satellite Data Assimilation Seminar: Ricardo Todling

[George Ohring - NOAA Affiliate]

* *

*JCSDA Seminar*

*Title*

*Hybrid Data Assimilation without Ensemble Filtering***

*Speaker*

*Ricardo Todling
NASA/Global Modeling and Assimilation Office*

*Date,  Time & Place*

*Wednesday, January 16, 2013
*2:00 – 3:00 PM
Conference Center, NOAA Center for Weather and Climate Prediction, 5830
University Research Court, College Park, MD

*Abstract*

The Global Modeling and Assimilation Office (GMAO) is close to upgrading
its system with a hybrid-ensemble analysis. Initially this effort has
followed the pathway taken by the National Centers for Environmental
Prediction (NCEP) in adding to its three-dimensional variational (3d-Var)
analysis a 3d ensemble Kalman filter (EnKF). The EnKF provides an ensemble
of analyses used to generate an ensemble of backgrounds for the hybrid
Grid-point Statistical Interpolation (GSI) analysis. Two steps link the
EnKF with GSI: re-centering of the ensemble members around the GSI
analysis; and addition of inflating errors to the re-centered ensemble
analyses to mimic the effect of model error. At first GMAO avoided this
latter step given it is theoretically difficult to justify it. Under
re-centering only, we quickly found there was no clear benefit from the
hybrid approach; with additive inflation, the hybrid strategy surely
brought in the expected improvements. The key role played by these additive
perturbations, created from 48-minus-24 hour forecast differences, led us
to consider a situation where an ensemble of analyses is generated by
simply adding these perturbations to the central analysis. This
presentation compares this alternative to the original implementation. The
proposed scheme leads to computational savings and avoids need to maintain
two analysis systems.

*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

*Seminar File*

Slides available prior to, and audio recording after, the presentation at
http://www.jcsda.noaa.gov/JCSDASeminars.php
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