Report from DAOS-WG (Data Assimilation and Observing Systems) Presented by Tom Hamill NOAA Earth System Research Lab Physical Sciences Division ([email protected]) Prepared by Tom Hamill and Roger Saunders, with input from WG members
presented at GIFS-TIGGE meeting, Boulder CO, June 2012
Current membership
Ron Gelaro(D),
Co-chair
NASA, USA
Roger Saunders(O),
Co-chair
Met Office, UK
Stefan Klink(O)
DWD, Germany
Carla Cardinali(D)
ECMWF
Chris Velden (O)
Univ Wisconsin -
CIMSS, USA
Tom Hamill(D)
NOAA/ESRL, USA
Tom Keenan (O)
CAWCR, Australia
Rolf Langland (D)
NRL, USA
Bertrand Calpini (O)
MeteoSwiss, Switzerland
Andrew Lorenc (D)
MetOffice, UK
Florence Rabier(D/O)
Météo-France
Prof. Bin Wang(D), Chinese
Academy of Sciences,
China
Michael Tsyrulnikov (D)
HydroMet Centre,
Russia
Mark Buehner (D)
Environment Canada
Sharan Majumdar (D)
RSMAS, University of
Miami, USA
O=Observations D=Data Assimilation
DAOS-WG objectives
Address data assimilation issues, including the
development of improved understanding of the sources of
errors in analyses and forecasts and growth of errors
during data assimilation cycle.
Promote research activities that lead to the better use of
observations for global NWP and an understanding of their
value.
Provide input and guidance for THORPEX regional
campaigns for the deployment of observations to achieve
scientific objectives.
DAOS-4 WG meeting Exeter 27-28 June 2011
• Reviewed targeting paper; updates on THORPEX campaigns; reviewed observing systems; reviewed developments in data assimilation
Observation impact, NRL (US Navy, US NASA, Canadian Met Centre)
In three different NWP systems a quantification of the overall impact of various
observation types using adjoint methods. See Gelaro et al., MWR, Nov 2010.
ECMWF observation impact
Ref: Cardinali, QJRMS 2009, DOI: 10.1002/qj
Similar dominance of AMSU-A. AIRS also big impact (not in Gelaro study)
Sharanya Majumdar,
U. Miami, generated
a report for THORPEX
(and eventual BAMS
article) summarizing
targeted observation
research.
Targeting statement, WMO meeting, Sedona, AZ, USA (May 2012)
• "The THORPEX-DAOS working group recently delivered its
comprehensive report on observation targeting. Its main message is
that there has been a paradigm shift in targeting with respect to 8
year ago; there is now less optimism about targeting having a
breakthrough impact in the extra-tropics. While the scientific
principle of improving forecasts with targeted observations has been
validated, the goal of adding sufficient observations over the entire
target subspace has proven to be logistically difficult to achieve.
Thus, the potential benefits in terms of forecast skill improvements
have not been fully realized. Targeted observation has, however,
been demonstrated to be effective for tropical cyclone forecasting,
through the use of dropsondes and rapid-scan satellite winds. The
targeted use of off-time (06UTC and 18UTC) radiosonde data has
been shown to improved mid-latitude forecasts."
Impact of assimilating dropsondes on typhoon track error during summer T-PARC
Tropical cyclone track forecast errors during the Summer T-PARC period for
four assimilation-forecast systems. The solid (dashed) lines represent
parallel analysis-forecast cycles excluding (including) T-PARC
dropwindsonde data.
Demonstrates generally positive results in assimilation of targeted data for TCs
Impact of targeted observations in mid-latitudes
- Previous studies: targeted obs. in dynamically sensitive
regions (via dropsondes) can improve downstream
forecasts in small target regions.
- Studies are now old, when obs. network was thinner and
data assimilation and forecast models less advanced. What
about with modern systems? Impact over broader areas?
- NOAA THORPEX-funded study: using N. Pac. targeted
dropsondes during 2011 winter, perform parallel
assimilations and 5-day deterministic forecasts with and w/o
additional data, using T511 ECMWF model and their 4D-Var
system.
- Conclusion: no evidence for positive impact on metrics over
broader regions. For limited-area regions, still being
evaluated.
Precipitation Threat Skill Scores over CONUS 12-36 hour Forecast
Entire CONUS Western CONUS
No statistically significant differences
12
The Concordiasi Project: additional
observations over Antarctica for NWP
F. Rabier, V. Guidard, S. Noton-Haurot, A. Doerenbecher, D. Puech,
P. Brunel, A. Vincensini, H. Bénichou, Météo-France
Ph Cocquerez, CNES
A. Hertzog, F. Danis, IPSL/LMD
T. Hock, S. Cohn, J. Wang NCAR
C. Sahin, A. Garcia-Mendez, J-N Thépaut ECMWF
A. Cress, U. Pfluger, DWD
R. Langland, NRL
G. Verner, P. Koclas, CMC
R. Gelaro, NASA/GMAO
C. Parrett, R. Saunders Met Office
Y. Sato JMA
for more information, see Jan 2010 BAMS
& tinyurl.com/concordiasi and supplementary slides
13
CONCORDIASI: stratospheric super-pressure balloons flight trajectories Sept 2010-January 2011
19 balloons
launched,
13 w. driftsonde.
Drops ~ coincide
with satellite
overpasses.
14
Sea-Ice limit
640 Dropsondes (20100923-20101201)
Participants CMC DWD ECMWF GMAO Météo-France Met Office JMA
Data assimilation monitoring statistics over the Antarctic
RMS(O-F) Obs Count
Radiosonde Background Temperature Departures (O-F)
Courtesy F. Rabier, Météo-France
All models have difficulty predicting lowest-level temperatures
16
Concluding remarks on ConcordIASI
Concordiasi provided an unprecedented data coverage of meteorological observations over Antarctica
Both dropsonde and gondola information seem to have a positive impact on forecast performance (preliminary results from NRL, DWD, ECMWF and MF)
Gondola temperature data at 60hPa shows the largest model errors in areas of strong gravity-wave activity
Dropsonde information confirms statistics obtained with radiosondes and provide a more global view
Most models have problems predicting the lowest level temperatures.
Development of advanced data hybrid assimilation systems
Methods of hybridizing 4D-Var with ensemble-based
assimilation techniques a very active area of research and
development at many agencies (e.g., CMC, ECMWF, UK
Met Office, NCEP).
Idea is to leverage advantages of both ensemble-based
and variational systems.
More on this in Weds. talk by Jeff Whitaker, NOAA/ESRL.
Use analyses for verification? Evaluation with TIGGE data.
Also, can we learn something about the sources of errors in
analyses?
Can monitoring of analysis differences help detect problems
at various operational centers?
Full presentation at
http://www.esrl.noaa.gov/psd/people/
tom.hamill/analysis-errors-wgne-hamill.pdf
In following slides, examined statistics from a year’s worth of
00Z analyses from CMC, NCEP, ECMWF, UK Met Office,
CMA.
Analysis spread, 250 hPa u component
What’s going on
in tropical
eastern Pacific
and tropical
western Indian
Oceans?
19
Time series of 250 hPa u-wind, eastern equatorial Pacific
CMC, and to lesser extent NCEP,
have much stronger westerly
winds.
20
Time series of 250 hPa u-wind, eastern equatorial Pacific (smoothed)
21
There are periods of time where
both NCEP and CMC are quite
inconsistent, even in time means,
with other analyses.
Consistency of others does
suggest that perhaps there are
some underlying problems with
these two analyses during
certain periods, and actually
with their removal, there may be
a decent consensus on the
wind analysis.
Challenge of data sharing: precipitable water observations available from E-GVAP
There is actually decent coverage of GPS
total precipitable water information over
US, but the data is not shared and
assimilated for lack of (modest) funds to
convert data to internationally agreed-upon
formats & to develop forward operators.
This highlights a general issue of
challenges of sharing data internationally.
c/o Seth Gutman, NOAA/ESRL
Challenge of data sharing: precipitable water observations available from E-GVAP
NCEP Stage IV obs (mm/day)
CTRL – NCEP Stage IV
NEW – NCEP Stage IV
Impact of NCEP Stage IV assimilation
on +12-h forecasts of precipitation.
Sept-Oct 2009 average
(ECMWF, CY35R2; T511 L91)
ECMWF 2011, Philippe Lopez
Example of benefits of sharing data: ECMWF using US radar-based precipitation estimates
Impact on forecast scores for other parameters (Z, T, wind, RH):
- neutral or slightly positive impact on the global scale.
- some hint of positive impact over Europe (days 4-5) and Asia (days 8-10).
Direct 4D-Var assimilation of NCEP Stage IV rain data in ECMWF
E
CM
WF
20
11
RMSE South. Hemis. 500hPa wind
RMSE NH. 500hPa wind RMSE Europe 500hPa temperature
RMSE Asia 850hPa Temperature
good
1 April – 6 June 2010,
T1279 (~15 km global) L91
Satellite data: data availability, new sensors
Hoping for extended life of polar-orbiting satellites to
minimize gaps until US JPSS operational (next slide).
• Contribution to global observing system by other nations increasing (e.g. FY-3 [China], Oceansat-2 [India]) – help fill gaps?
• Hyperspectral sounder now approved by Europe on MTG (Meteosat 3rd-generation, GEO orbit, ~2017).
• Canada evaluating constellation of highly elliptical orbit satellites, possibly deployed as early as 2018-19
27
Satellite data processing issues
• Currently only a fraction of the satellite data available is assimilated, in part due to concerns about correlations of errors degrading assimilations.
• Recent research suggests reduced thinning of AMSU-A may be beneficial (ECMWF, Meteo Fr.).
• Selection of dynamically important regions for assimilating data at higher resolution of interest, radiances or rapid-scan motion vectors.
• Extending the use of satellite data in cloudy regions an area of active research.
• Only one scatterometer now
typically assimilated (ASCAT),
with loss of Quikscat. Narrower
swath width than Quikscat,
though.
• Right: ASCAT winds for Irene
and model background
• Trials and monitoring ongoing
using scatterometer on India’s
Oceansat-2.
• Scatterometer not planned for
US’s JPSS due to budget
constraints.
Importance of scatterometer winds
DAOS-WG directions, issues
• DAOS is leading group for DA in WMO (some in WGNE, too). What is its future in WWRP after THORPEX?
• New co-chair, new members, esp. S. American representative
• Improve WMO connections, especially with:
• ET-EGOS (expert team on evolution of global observing system)
• SPARC (Stratospheric Processes/Climate)
• GLASS (Global Land-Atm. System Studies)
• Next meeting in Madison, WI, USA 19-20 Sep 2012
• Also: upcoming DWD DA symposium, Oct 2012
• Joint meeting with MFWR (mesoscale weather forecasting research) under discussion
• DAOS expects to retain its global focus but link more with mesoscale
• Continue deliberating both on observing systems issues and assimilation techniques.
30
DAOS-WG Statement on impact of targeted data
• For mid-latitude systems, the value of targeted data is found to be positive but
small on average. The US Winter Storms Reconnaissance Program has found
that targeting results in some improvement in 2-3 day forecasts over N. America.
• Observations in dynamically sensitive areas have a bigger average impact per
observation than those deployed randomly. The cumulative benefit of a small
number of targeted aircraft observations to forecast accuracy over broad
verification regions is smaller than that of other observing systems that provide
observations with a more complete coverage.
• For forecasts of the track of TCs targeted observations have proven to be
beneficial statistically. A simple sampling strategy of observing uniformly around
the TC has been shown to be effective, with most models exhibiting an
improvement.
• There is a need to assess the impact of targeted observations with more user-
focused measures of the value of forecast improvements to society, while
retaining the ability to get significant results from relatively short experiments.
c/o Fanglin Yang, NCEP/EMC
Anomaly correlation over Pacific – North America region
over too broad a region to see impact?
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