[Proflist] Joint Center for Satellite Data Assimilation Seminar, November 10th: Thomas Nehrkorn

[Ana Carrion - NOAA Affiliate]

*JCSDA Seminar*

*Title*

*Correcting for Position Errors in Variational Data Assimilation*

*Speaker*

*Thomas Nehrkorn*

*Modeling and Data Assimilation Group, Atmospheric and Environmental
Research, Inc (AER)*

*Date,  Time & Place*

*November 10, 2014, 2:00 pm – 3:00 pm*
Conference Center, NOAA Center for Weather and Climate Prediction, 5830
University Research Court, College Park, MD

*Abstract*

Forecasts used in variational data assimilation schemes for the atmosphere
and ocean often exhibit significant position errors. In standard data
assimilation approaches position errors often result in background errors
that have complex error correlations, are not normally distributed, and are
particularly difficult to correct. A number of approaches have been
proposed to measure and correct position or phase errors, ranging from
techniques originating from image processing such as "image warping" or
"morphing" and "optical flow," object-oriented verification measures, to
alignment approaches aimed at data assimilation improvements.

We present an implementation of a displacement scheme to correct phase
errors based on the feature calibration and alignment (FCA). In its
original formulation, a set of two-dimensional displacement vectors is
applied to forecast fields to improve the alignment of features in the
forecast and observations. These displacement vectors are obtained by a
nonlinear minimization of a cost function that measures the misfit to
observations, along with a number of additional constraints (e.g.,
smoothness and non-divergence of the displacement vectors) to prevent
unphysical solutions. Results from this implementation will be compared
with a more recent implementation within the WRF-Var (WRFDA) algorithm, in
which the nonlinear minimization is replaced by the (linear) conjugate
gradient inner-loop minimization combined with outer loop nonlinear
adjustments, and the ad-hoc penalty function constraints are replaced by an
error-covariance representation of the displacement vectors.

*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. No password is necessary 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 Erin.Jones at noaa.gov

*Seminar Files*

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



-- 

*Ana Carrion*
National Oceanic and Atmospheric Administration
Program Support Specialist
Riverside (RTi) at NOAA/NESDIS/STAR/JCSDA
NCWCP, E/RA, Room #2652
5830 University Research CT
College Park, MD 20740-3818

Email: Ana.Carrion at noaa.gov
*Main Line**: 301-683-3520*
*JCSDA Front Office: 301-683-3615*
*STAR Front Office: 301-683-3485 *
Fax: 301-683-3526
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