Report from DAOS-WG (Data Assimilation and Observing Systems)

Transcription

1 Report from DAOS-WG (Data Assimilation and Observing Systems) Presented by Tom Hamill NOAA Earth System Research Lab Physical Sciences Division Prepared by Tom Hamill and Roger Saunders, with input from WG members presented at GIFS-TIGGE meeting, Boulder CO, June 2012

2 Current membership Ron Gelaro(D), Co-chair NASA, USA Carla Cardinali(D) ECMWF Tom Keenan (O) CAWCR, Australia Roger Saunders(O), Co-chair Met Office, UK Chris Velden (O) Univ Wisconsin - CIMSS, USA Rolf Langland (D) NRL, USA Stefan Klink(O) DWD, Germany Tom Hamill(D) NOAA/ESRL, USA Bertrand Calpini (O) MeteoSwiss, Switzerland Andrew Lorenc (D) MetOffice, UK Michael Tsyrulnikov (D) HydroMet Centre, Russia Florence Rabier(D/O) Météo-France Mark Buehner (D) Environment Canada Prof. Bin Wang(D), Chinese Academy of Sciences, China Sharan Majumdar (D) RSMAS, University of Miami, USA O=Observations D=Data Assimilation

3 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.

4 DAOS-4 WG meeting Exeter June 2011 Reviewed targeting paper; updates on THORPEX campaigns; reviewed observing systems; reviewed developments in data assimilation

5 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.

6 ECMWF observation impact Similar dominance of AMSU-A. AIRS also big impact (not in Gelaro study) Ref: Cardinali, QJRMS 2009, DOI: /qj

7 Sharanya Majumdar, U. Miami, generated a report for THORPEX (and eventual BAMS article) summarizing targeted observation research.

8 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."

9 Impact of assimilating dropsondes on typhoon track error during summer T-PARC Demonstrates generally positive results in assimilation of targeted data for TCs 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.

10 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.

11 Precipitation Threat Skill Scores over CONUS 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 12 & tinyurl.com/concordiasi and supplementary slides

13 CONCORDIASI: stratospheric super-pressure balloons flight trajectories Sept 2010-January balloons launched, 13 w. driftsonde. Drops ~ coincide with satellite overpasses. 13

14 640 Dropsondes ( ) Sea-Ice limit 14

15 Data assimilation monitoring statistics over the Antarctic Radiosonde Background Temperature Departures (O-F) RMS(O-F) Obs Count Participants CMC DWD ECMWF GMAO Météo-France Met Office JMA All models have difficulty predicting lowest-level temperatures Courtesy F. Rabier, Météo-France

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. 16

17 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.

18 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 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.

19 Analysis spread, 250 hpa u component What s going on in tropical eastern Pacific and tropical western Indian Oceans? 19

20 Time series of 250 hpa u-wind, eastern equatorial Pacific CMC, and to lesser extent NCEP, have much stronger westerly winds. 20

21 Time series of 250 hpa u-wind, eastern equatorial Pacific (smoothed) 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. 21

22 Challenge of data sharing: precipitable water observations available from E-GVAP

23 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. c/o Seth Gutman, NOAA/ESRL This highlights a general issue of challenges of sharing data internationally.

24 Example of benefits of sharing data: ECMWF using US radar-based precipitation estimates Impact of NCEP Stage IV assimilation on +12-h forecasts of precipitation. Sept-Oct 2009 average (ECMWF, CY35R2; T511 L91) CTRL NCEP Stage IV ECMWF 2011, Philippe Lopez NCEP Stage IV obs (mm/day) NEW NCEP Stage IV

25 ECMWF 2011 Direct 4D-Var assimilation of NCEP Stage IV rain data in ECMWF 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). RMSE NH. 500hPa wind RMSE Europe 500hPa temperature good RMSE South. Hemis. 500hPa wind RMSE Asia 850hPa Temperature 1 April 6 June 2010, T1279 (~15 km global) L91

26 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 3 rd -generation, GEO orbit, ~2017). Canada evaluating constellation of highly elliptical orbit satellites, possibly deployed as early as

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28 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.

29 Importance of scatterometer winds 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.

30 30 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 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.

31 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 userfocused measures of the value of forecast improvements to society, while retaining the ability to get significant results from relatively short experiments.

32 Anomaly correlation over Pacific North America region c/o Fanglin Yang, NCEP/EMC over too broad a region to see impact?