3 rd THORPEX DAOS Working Group meeting

1. 3rd THORPEX DAOS Working Group meeting • Objective • Review the issue of adaptive observations • Results from T-PARC (winter phase and TCS-08) • Update on other campaigns and activities • Review paper on the value of targeted data to be published in peer-review literature (BAMS) • Presentations available at • http://web.sca.uqam.ca/~wgne/DAOS/DAOS3_meeting/

2. DAOS-WG recommendations for Targeted Observing Field Programs • Impact of targeted observations from previous field programs (esp. WSRP, ATreC-2003TPARC) • Expensive observation campaigns should not be justified based only on previous methods of targeting • Rabier et al. (2008) • Carefully consider data assimilation issues (impacts of small vs. large sets of observations, frequency of special observations, etc. ) • Develop and test new adaptive strategies • Adaptive selection and assimilation of satellite observations (less than 10% of available data currently used)

3. Observability of a structure function(Lupu and Gauthier, 2010) • Correlation between the innovations and a structure function v • This defines the observability of a structure functions • Can the observations detect a given structure function?

4. Observability of different structure functions based on key analyses

5. The intercomparison experiment on the impact of observations • A goal of THORPEX is to improve our understanding of the ‘value’ of observations provided by the current global network • optimize the use of current observations • inform the design/deployment of new obs systems • In 2007, DAOS-WG proposed a comparison of observation impacts in several forecast systems, facilitated by the emergence of new (adjoint-based) techniques • Experiments for a baseline observation set were designed by DAOS members from NRL, GMAO, EC, ECMWF, Météo-France • …so far, results obtained for 3 systems: NRL, EC, GMAO

6. Singular vector-based thinning of satellite data Peter Bauer, Roberto Buizza, Carla Cardinali and Jean-Noël Thépaut European Centre for Medium-Range Weather Forecasts

7. Conclusions • The ECMWF current operational setting (1.25) is too conservative and satellite data density could be increased. • 0.625thinning will be considered for operational implementation. • Volume increase can be kept to affordable levels if satellite data density is increased only in a selective way. This study has shown that over the SH, singular vector-based satellite data thinning is a strategy that can lead to better analyses and lower forecast errors. Results are seasonal dependent: • In JAS08 the impact of the extra data is small. DFS indicates that less information was extracted from the obs located in the SV-area than in other regions. Eady index statistics indicate that perturbation grow faster, and this could explain why other sources of forecast errors becomes as important as initial condition. • In D08JF09, all targeting experiments (EXP-SV/CLI/RND) perform better than EXP for a longer period. Of the three targeting experiments, EXP-SV gives the best results, very similar to EXP-HI after 72h. DFS of obs located in SV-areas is larger than the DFS of obs located in other regions. Perturbation growth is slower (Eady index) and initial condition errors are dominant for a longer time period. The day-2 average forecast error reduction of ~4% detected for Z500 over SH is equivalent to a predictability gain of ~1 hour.

8. Left: AMV (IR-only) field produced from routinely available hourly sequence of MTSAT-1 images during Typhoon Sinlaku Bottom Left: Same as above, but using a 15-min rapid scan sequence from MTSAT-2 (better AMV coverage and coherence) Bottom Right: Same as above, but using a 4-min rapid scan sequence (improved coverage/detail of typhoon flow fields) Example of AMVs from MTSAT-2 Rapid Scan images

9. TC Diagnostic Studies using High-Res. Rapid-Scan AMVs Example: Typhoon Sinlaku during TPARC 150 hPa Divergence analyzed from upper level R/S AMVs 150 hPa Vorticity analyzed from upper level R/S AMVs

10. Review of the impact of targeted data • Community paper being written • Lead author is SharanMajumdar with contributions from the DAOS-WG and scientists involved in targeting campaigns (including Y. Song and Z. Toth) • Reconcile seemingly opposing views on the impact of targeted data • Summary of results obtained so far • Identify issues that need to be addressed to improve the use of observations that impact weather forecasts (e.g., metrics, assimilation methods, sampling of precursors to dynamic instability)

11. Conclusion • THORPEX data assimilation and observing systems working group has reached a mature stage • Focus on fundamental issues associated with data assimilation to improve forecasts • Links with CBS, satellite agencies and NWP Centres • WMO does not have a specific working group on data assimilation • Important for model validation and reanalysis

12. Current status of WGNE • Representatives from a number of other expert working groups (e.g, GLASS, GCISS, SPARC) on top of representatives from operational centres • Numerous data assimilation issues emerge in different groups • Is there a need to provide a forum to discuss DA issues specifically? • The WMO Data Assimilation Symposium provides an occasion to discuss progress in data assimilation in different areas (oceanography, meteorology, atmospheric chemistry, land surface, analysis for climate, etc…) • Advice to Expert Team on the Global Observing system. • Discussions at WGNE were about providing a voice on WGNE to summarize progress, issues and recommendations on DA and observations in support for modeling

13. Historical perspective from Andrew Lorenc • WGNE was a pioneer in OSSE studies ( Andrew went to WGNE organised conferences in 1970s!).  • The discussions transformed into reports as ET-EGOS CBS-OPAG/IOS Expert Team on the Evolution of global observing systems took over. • WGNE was a pioneer in advocating re-analyses, and a major player in organising conferences.  I believe that is now "owned" by GCOS. http://reanalyses.org/ • WGNE was involved in organising the regular WMO DA Symposia • each seems to actually depend on an ad hoc selection of organizers • It would be good to have a group to "own" this series. • WCRP Observations and Assimilation Panel is also interested in reanalysis. • SPARC DA organises regular meetings. • WGNE is interested in several THORPEX activities, including those of DAOS • WWRP Mesoscale DA group

14. Issues to discuss • Is there a need for a central structure to coordinate research related to observations and data assimilation? • The THORPEX-DAOS is seen to be the best candidate to take the lead • Representatives from other working groups to link with DAOS (GLASS, SPARC, Mesoscale Data assimilation, …) could attend our meetings • Mandate for the organization of the WMO Symposium on Data assimilation • Link between DA and modeling must be preserved • DA is a lot about model validation and it may be more natural to have bodies that foster this linkage (e.g., SPARC-DA) • There may be an interest to have DA specific issues discussed with others (e.g., the DA problems are not always about improving a forecast)

15. Organisational aspects • The THORPEX working groups • Discussions on moving them up to the WWRP level once the THORPEX programme is over (already happened with SERA) • WGNE is a joint WCRP-WWRP working group and then needs to cover climate modeling and DA issues • Covering all aspects of DA exceeds by far the THORPEX objectives • WGNE is considering to have data assimilation as its main theme for 2012 or 2013 • DA at higher resolutions • Reanalyses