Transcript 3rd THORPEX DAOS Working Group meeting • Objective * Review the issue of adaptive observations * Results from T-PARC (winter phase and TCS-08) *

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/
DAOS-WG recommendations for Targeted
Observing Field Programs
1. 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)
2. Carefully consider data assimilation issues (impacts
of small vs. large sets of observations, frequency of
special observations, etc. )
3. Develop and test new adaptive strategies
* Adaptive selection and assimilation of satellite
observations (less than 10% of available data
currently used)
Observability of a structure function
(Lupu and Gauthier, 2010)
• Correlation between the innovations d  y  Hxb and
a structure function v
ρ
(Hv)T R 1d
1/2
(Hv) R (Hv) 
T
1
1/2
d R d
T
1
• This defines the observability of a structure
functions
* Can the observations detect a given structure function?
Observability of different structure functions based on
key analyses
Structure
functions
GLOBAL
LOCAL
HEMISPHERIC
PV-BAL
r, correlation coefficient
Obs. type
January 27,
2003
January 06,
2003
February
06, 2002
January 19,
2002
RAOB
0.01
0.02
0.03
-0.01
AIREP
0.00
0.02
-0.01
-0.01
ATOVS
0.13
0.11
0.07
0.12
TOTAL
0.05
0.05
0.05
0.03
RAOB
-0.01
0
-0.01
-0.02
AIREP
-0.03
-0.01
-0.03
-0.03
ATOVS
0.05
0.01
0.06
0.02
TOTAL
0
0
0
-0.01
RAOB
0.00
0.02
0.01
0.01
AIREP
-0.05
0.02
-0.02
-0.03
ATOVS
0.08
0.07
0.07
0.04
TOTAL
0.03
0.04
0.04
0.02
RAOB
0.01
0
0.01
0
AIREP
-0.03
0.01
-0.03
0
ATOVS
0.09
0.08
0.08
0.05
TOTAL
0.03
-0.01
0.06
0.02
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
Singular vector-based thinning
of satellite data
Peter Bauer, Roberto Buizza,
Carla Cardinali and Jean-Noël Thépaut
European Centre for Medium-Range Weather Forecasts
Exeter May- Bauer et al: Singular vector-based thinning of satellite data
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.
Exeter May- Bauer et al: Singular vector-based thinning of satellite data
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Example of AMVs from MTSAT-2 Rapid Scan images
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)
TC Diagnostic Studies
using High-Res. RapidScan 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
Review of the impact of targeted data
•
Community paper being written
*
•
Lead author is Sharan Majumdar 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)
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
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
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
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)
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