[Mitgcm-support] Note: February 8, 2001

Wed Jul 9 15:56:07 EDT 2003

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NOTES FROM THE ASSIMILATION MEETING : 8 February 2001    

1) K-filter 
------------
   - A summary of runs calibrating process noise (Q) have been posted[1].
     Process noise needs to be calibrated so that model errors are
     consistent with actual model-data differences.  Model errors must
     taper to zero at open cell boundaries to account for
     representation error.

     However, comparisons with independent data suggest runs with
     calibrated Q are actually worse than non-calibrated Q.  

===> Comparisons with TAO and XBTs to be summarized and
     posted [Dimitris].
===> Further calibration and/or adjustment is likely necessary
     [Ichiro/Benyang].  

   - Assimilation (and control run) has been extended to the end of
     the 3rd quarter in 2000.  The particular assimilation is kf029,
     and is a combined BC-BT filter using the calibrated Q of kf024i
     (BC) and kf022e (BT). 

   - A 5-mode BC filter is being prepared.  The code is being checked
     for consistency.   

===> The results of the 1-year adjoint below could be analyzed to
     examine the significance of higher baroclinic modes in correcting
     the model.  [Ichiro/Benyang/Tony]

2) Adjoint 
-----------
   - The 1-year adjoint has converged to an acceptable limit as
     reported here[2]. The Ames queue can now be used for;
          * Repeat T/P and Levitus assimilation for 1998
          * Process N.Smith's XBT data and assimilate that for 1997

===> Doing the '98 assimilation seems most rewarding [Tony/Benny].

   - Changes in wind stress accounts for most of the correction
     achieved by the 1-year adjoint.  Plots analyzing the model and
     wind correction is posted here[3].

     The wind corrections show patterns of westward propagation.
     Could these be due to air-sea coupling or is it an artifact of
     the assimilation?  W.White has found evidence for a westward
     propagating wind signal at mid-latitudes that he attributes to
     coupling. 

===> Changes in wind could be validated wrt NSCAT and/or TAO [Tony]. 

   - There appears to be a bug in Moto's package implemented in the
     ECCO code (and also in the latest version of the MITcode).
     Changes in surface temperature do not match the sum of terms
     controlling temperature.  Other depths are OK.  It is anticipated
     that the control run (c20000630 and Moto's analysis) were OK.

===> The gsgt package needs to be debugged [Dimitris]. 

   - Request to purchase TAF has been forwarded to procurement.

3) Figure for Eric 
-------------------
   - Two figures were prepared for Eric's NASA Report, both showing
     anomalies in November 1997.  The first figure[4] compares T/P sea
     level (top) and an assimilation estimate (lower) of heat content
     and surface velocity.  The second figure[5] compares assimilation
     estimates of temperature and velocity at the surface (top) and
     200m depth (bottom).  The assimilation estimate is T/P K-filter
     assimilation run kf024f.  Anomalies are with respect to '93-'95
     average seasonal cycle.

===> The figures (or a combined version) are to be put on our web-site
     [Dimitris/Tony/Ichiro/Zhangfan]. 

   - Further analysis of assimilation results point to other possibly
     intriguing mechanisms of change.  Evidence suggests tropical
     temperature change near the surface (at least above 200m) being
     mostly due to zonal advection.  At depth (~1200m), things look
     different; it shows Rossby wave-like patterns suggesting changes
     being dominated by vertical heaving.  There is a curious
     coincidence between what appears to be a reflected Rossby wave of
     the 97-98 ENSO reaching the western end in 1999 along 8N (~1200m)
     and the emergence of the negative PDO pattern at the surface.  

4) Other
---------
   - Directories on hpss have been changed.  All files have been moved
     to 
          /proj/ocsatmeas/xing
     etc.  Now all group members have read access to other members'
     files.

     [Somehow I now have to turn off the "passive mode" for my ftp to
     work with hpss.] 

   - Lee showed comparisons of ssh along 30N in the Pacific between
     T/P and c20000630 from 1993 till end of 1999.  There are
     similarities in large-scale westward propagating signals.  There
     appears to be a sudden increase in amplitude in 1994, coincident
     with a basin-wide wind event.

   - There is a problem with the automatic Legato backup for guppy and
     nautilus.  Zhangfan and I-Lin are working on it.  Make sure you
     are getting the automatic e-mail of backup information and that
     the backups are successful.  

   - There are several web-sites that provide images from
     assimilation.  They should be examined and used as a reference to
     implement something similar for our project.  These web-sites
     include; 
            DIADEM: http://diadem.halo.is/diadem/
            MERCATOR: http://www.mercator.com.fr/
            NSIPP: http://pong.gsfc.nasa.gov/index.html

     The NOAA OGP site has an animation of SST that runs in the
     browser; 
            http://www.ogp.noaa.gov/enso/animation.html

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[1] http://escher.JPL.NASA.GOV:2000/HyperNews/get/forums/assim/112/1.html
[2] http://escher.JPL.NASA.GOV:2000/HyperNews/get/forums/assim/110/1.html
[3] http://escher.JPL.NASA.GOV:2000/HyperNews/get/forums/assim/110/2.html
[4] http://escher.JPL.NASA.GOV:2000/hosts/escher/escher2/medea/if/forum/Dimitris/ODA.jpg
[5] http://escher.JPL.NASA.GOV:2000/hosts/escher/escher2/medea/if/forum/Tony/globe2.ps