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IPWG Validation current status and future directions

IPWG Validation current status and future directions. Chris Kidd Beth Ebert John Janowiak. The University of Birmingham, Birmingham, UK Bureau of Meteorology, Melbourne, Australia CPC/NCEP/NWS/NOAA, USA. 4 th International Precipitation Working Group (IPWG) Workshop

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IPWG Validation current status and future directions

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  1. IPWG Validationcurrent status and future directions Chris Kidd Beth Ebert John Janowiak The University of Birmingham, Birmingham, UK Bureau of Meteorology, Melbourne, Australia CPC/NCEP/NWS/NOAA, USA 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  2. IPWG validation sites Addresses IPWG objectives: #2) Establish standards for validation and independent verification of precipitation measurements #3) Foster the exchange of data on intercomparisons of operational precipitation measurements from satellites Main regions (initiated 2002) are: Australia, United States, Europe and South America, with Japan, South Africa and others for selected periods Common graphical, descriptive and statistical analysis of daily, 0.25° resolution products. 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  3. GV-IPWG synergies GV=Ground Validation After Turk & Arkin, BAMS 2008 Both approaches are complementary 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  4. Global precipitation data sets 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  5. IPWG Intercomparison regions Near real-time intercomparison of model & satellite estimates vs radar/gauge 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  6. 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  7. Processing system Initial setup: Setting of dates Cleaning out old/decayed data Remapping of data: … to regional grid or 5 km PSG projection… Results generation: Statistical analysis Graphical output Acquiring data: Searching existing data Listing missing data Creation of .netrc file ftp data sources Web pages: Generate HTML files Copying to server

  8. foreach day (d0-d0-31) foreach product & day dn=dn+1 remap to PSG using LUTs & standardise format set d0=today standardise filename foreach datasource (s0-sn) foreach product & day foreach product (p1-pn) Generate statistics foreach day (d0-d0-31) Generate plots N if (product for day) !exist Y foreach product & day add to .netrc file generate HTML files ftp datasource (4k) Processing checks

  9. foreach day (d0-d0-31) foreach product & day dn=dn+1 remap to PSG using LUTs & standardise format set d0=today standardise filename foreach datasource (s0-sn) foreach product & day foreach product (p1-pn) Generate statistics foreach day (d0-d0-31) Generate plots if (product for day) !exist Y N foreach product & day add to .netrc file generate HTML files ftp datasource (4k) Processing checks Set up list of past dates/days Usually okay: sometimes needs tweaking Prepares products into common format Usually okay… Checks for a products results: Okay if no results, but not if bad data Generates outputs: Okay if there is rain… Generates raw HTML: Occasional issues with server FTP runs several times: 4K buffer limit on macros Automated systems they are NOT!

  10. Validation products Both gauge and radar are used – depending upon the real-time accessibility to these data sets Australia: gauge analysis United States: gauge and radar analysis Europe: radar analysis South America: Gauge analysis European radar data: European composite with different radar and calibration and QC strategies; nominal 5km 15-minute product; available within ~1 hour; errors include range effects and anaprop (shipping, etc) Gauge data: 09-09Z data (dated at end of period); ~6000 daily gauges with mean 10km spacing; available 1 month in arrears 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  11. Radar vs gauge data Radar (daily integrated) Gauge data 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  12. Overall results • There is a clear seasonal dependence of satellite product performance (poorer in winter) • Models overestimate rain area/extent • Satellite products underestimate rain area/extent • Significant day-to-day variations • Surface contamination of satellite products noticeable in winter Performance dependent upon precipitation extent and intensity, spatial and temporal resolution of product – implications for high-resolution precipitation products 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  13. The future of IPWG validation regions What are the key requirements in the future to make best of our own limited resources? What are the requirements of the user community? What are the requirements of the algorithm/product developers? What new sources of data are available? Should we go beyond daily regional comparisons (local-global, instantaneous-seasonal)? 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  14. The future of IPWG validation regions New sites: • BALTEX region – limited number of algorithms (and need to read HDF5!); also Canada (limited coverage) • High-latitude oceanic location (Iceland; Shetlands?) • Broaden existing regions (e.g. Europe) New comparison techniques: • high-resolution products will need to rely upon descriptive statistics • implementation of fuzzy-logic statistical techniques New performance results: • Seasonal and global comparisons 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  15. The future of IPWG validation regions International framework Current European radar network – used in IPWG EUMETNET radar coverage 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  16. Latitude profiles: rainfall occurrence

  17. Monthly and seasonal validation Monthly and seasonal diagnostic validation summaries 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  18. The future of IPWG validation regions Suggested analysis levels: • real time analysis: 'correctness' of near real-time products: should these be easily available (cics?) • 'historical' analysis: 'authorised' release of quality-controlled products • high-resolution analysis: similar set-up to daily/0.25 degree products (including instantaneous) • 'training' data sets: example data sets from a comprehensive range of precipitation products – common naming convention and format 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  19. Personal recommendations Evaluation of combined techniques: • individual component products for combined algorithm • actual combination techniques Standardisation of precipitation product format • simple 2D arrays with accompanying text files • common format –variable size • quantitative resolution – 0.1 mm/day (WMO standard) • error fields can be accompanying files • Naming conventions standardised The IPWG gauntlet: …. to generate global 1km, 1 minute rainfall estimates…. 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

  20. Bacchiglione (1200 km2) Posina (116 km2) PMIR: 4km/30min 3B42RT: 1deg/3hr Anagnostou & Hossain: Satellite error propagation in flood prediction Northern Italy: Basin scales from 116 to 1200 km2, storm induced flash flood event (Nov 1996) Satellite products: Kidd, 1h/4km, and 3B42, 3h/25km: reference rainfall: radar at 1h/1km Ensembles generated based on SREM2D; Hydrological model simulations based on tRIBS distributed rainfall-runoff model High resolution products do work!

  21. Recommendations To establish guidelines for satellite precipitation product data: establish common criteria that can and will be used to promote long-term data sets To widen our validation regions to provide globally representative (inter)comparisons: at daily scales, but also monthly and seasonal scales. Investigate statistical tests that are more relevant to the data sets we are dealing with, and that be applied over a range of spatial and temporal scales To promote near real-time high resolution (sub-daily, <0.25 degree) precipitation inter-comparisons 4th International Precipitation Working Group (IPWG) Workshop 13-17 October 2008 Beijing, China

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