1. CRTF Progress Report on some GAEA Reanalysis Issues and Experiments
NCEP HYBRID/ENKF throughput issues on GAEA
Reanalysis experiment descriptions relevant to this report
HYBRID vs 3DVAR forecast quality in period
HYBRID vs 3DVAR QBO response in period
HYBRID QBO Response compared with ERAINT and JRA55
Conclusions and next steps
Jack Woollen
Thanks to the CPC Reanalysis group for help and ideas facilitating this work
Arun Kumar
Craig Long
Leigh Zhang
Shuntai Zhou
Wesley Ebisuzaki
New member Hyun-Chul Lee

2. Hybrid runs on GAEA average between 5-6 days/day
Hybrid/ENKF Timing diagram
PREP
Possible throughput:
3.34hr/day =7.2 days/day
Real throughput:
5d/d=7.3hr dead time/day
6d/d=4.0hr dead time/day
Cause of dead time:
Q wait between batch jobs
Conclusion:
Need to consolidate batch jobs into bigger jobs to get more throughput
GSI
EOBS
EOMN
EUPD
26:20
FCST/POST
ECEN
Jeff has mentioned he already didi this with the ENKF part, which we can benefit from his experience. I think we can start the consolidation of the NCEP scripts by running the ensemble analysis and forecast jobs to one batch job each and move on from there.
EFMN
23:50
EPOS

3. Reanalysis Experiments discussed in this report
HYBRID/ENKF
PRHL4
July1981-
July1982
Hybrid control run with T254/T126/L64 NCEP operational Hybrid/ENKF analysis/forecast system
3DVAR
PRHL5
3DVAR control run with T254/L64 NCEP operational GSI analysis/forecast system
PR3DV
3DVAR experiment like PRHL5 with modified 12hr analysis window for raobs in tropical stratosphere above 20mb
PRHN4
Sep1981-
May982
Hybrid like PRHL4 with modified QC to assimilate all rocketsonde data above 5mb in the tropical stratosphere
was chosen because CFSR had so much trouble in that period. Mostly because the GSI was configured for 2007 and didn’t work well with the 1980s data distribution, and the sat bias correction was not setup correctly for SSU data which impacted nearly the whole atmosphere.

4. Five day 500mb height forecast quality is fairly good for the time period in all three systems in both hemispheres.
Similar ranking of results is seen in nearly all levels, variables, and regions where anomaly corrections have been calculated.
The improvement in 3DVAR quality over CFSR (T254 vs T382) is likely due to model changes and much improved bias correction methodology applied to TOVS data.

5. The HYBRID/ENKF forecasts are significantly better than 3DVAR or CFSR uniformly in both hemispheres and nearly all lengths and regions.

6. Time series of analysis, guess, f12-f48 forecast fits to raobs PRHL4 vs PRHL5. A feature of the difference between hybrid and 3dvar systems is illustrated by the hybrid analysis fitting data less well than the 3dvar system, but the hybrid forecasts are uniformly better at all lengths. This could be seen as the situation dependent forecast error structure in the hybrid correcting the background more in some places and less in others, rather than the more “blanket” corrections made by 3dvar. Hybrid corrections are “smarter”, resulting in better forecasts, in general.
HYBRID
3DVAR
Daryl: About the hybrid analysis fitting data less well, this is to be entirely expected given the change in the degrees of freedom in background error within the ensemble context.  This can be overcome by tuning the amplitude of the ensemble, so some of it is likely an artifact of choices made for the inflation parameters (which strongly control the ensemble spread). We are working toward the use of stochastic physics as a replacement for the additive inflation as it is a more realistic method for treating model/system uncertainty.

7. Comparison of QBO response between NCEP HYBRID vs 3DVAR reanalysis systems shows clearly the advantage of the hybrid methodology in data sparse regions. The red lines are 4day running means of the u-wind observations. The green are 4day running means of the analysis at the data points. The blue is the time series of the analysis mean uwind in +/- 10 degrees latitude. The boxes at the bottom show the daily ob count with green accepted and red rejected.
HYBRID
3DVAR
The following graphs all represent the mean uwind in +/-10 degree lat zone. The next 2 slides show ob counts w/qc at the bottom.

8. It was supposed that extending the analysis window to 12 hours above 20mb in the tropics might help the 3DVAR draw more to the data and reject less observations. In the plot below right is seen the outcome of this. More data is used and the rejection rate is lower, and the system draws closer to the data, but only marginally. Possibly, looser VarQC cutoffs may help, and along with larger scale forecast error structure specified for this region.
3DVAR
3DVAR w/12hr window

9. Compare Hybrid QBO Response with JRA55 and ERAINT 50-30-20mb all fairly close to data and each other

10. Compare Hybrid QBO Response with JRA55 and ERAINT 10mb has varied results – ERAINT closest overall to the data

11. The difference between PRHL4 and ERAINT seemed in part due to many rejected rocket-sonde winds in the HYBRID. The plot labeled prhl4-erint below left shows the rejected data by + overlaid on the difference. The plot below right shows the same comparison with PRHN4, like PRHL4, but with wind data above 5mb retained. When the data is assimilated, the HYBRID differences from ERAINT diminish somewhat. This appears to be the cause of the HYBRID westerly hump in Apr-May 1982, and suggests that a loosening of the VarQC tolerances for wind in the tropical stratosphere is important.
Up to May 01
From Daryl: I suspect this isn't just a QC issue, and the ensemble covariances at these levels are sub-optimal.  This is where I think stochastic physics could be a significant help (in terms of generating more realistic/usable covariances).  Perhaps you should try something like what we are configuring for the next implementation (much smaller additive inflation, turn on some of the stochastic phycics).  It would need to some tuning of the parameters to get it right and hopefully we can work with Jeff Whitaker's on this.

12. PRHN4 resembles a cross between ERAINT and JRA55!
Compare Hybrid QBO Response with JRA55 and ERAINT PRHL4 10mb contrasted with PRHN4 (using rocketsondes)
PRHN4 resembles a cross between ERAINT and JRA55!
It becomes pretty clear that the selection of data to assimilate in the upper QBO region is a significant issue and it seems like each reanalysis addresses this problem differently. Of course, since the data is so sparse, the models play into the different outcomes also.

13. Conclusions and Next Steps Along these Lines
Hybrid/ENKF system as ported from ZEUS gives good results in test period, significantly better than CFSR everywhere
3DVAR system performs better than CFSR but needs more work to diagnose and address problems especially at the edges, especially the tropics and the stratosphere
Both systems could benefit from loosened VarQC cutoffs in the tropical stratosphere, the 3DVAR needs larger scale tropical forecast error structure
The next period to look at with HYBRID/ENKF is beginning 1960 to see the transition to ON20 observations including regular aircraft data receipt in 1962
The next period scheduled for 3DVAR experiments is to examine the TOVS/ATOVS interface starting in late 1998
The End – Thanks!