The International Precipitation Working Group Arnold Gruber – NOAA/NESDIS, Camp Springs, MD, USA

1. The International Precipitation Working Group Arnold Gruber– NOAA/NESDIS, Camp Springs, MD, USA and Vincenzo Levizzani– CNR/ISAC, Bologna, Italy

2. International Precipitation Working Group (IPWG) • Established June 2001- Workshop at CSU Tamasag Conference Facility, Fort Collins, Colorado, USA • Objectives : • 1) to promote standard operational procedures and common software for deriving precipitation measurements from satellites; 2) to establish standards for validation and independent verification of precipitation measurements derived from satellite data; including: • reference standards for the validation of precipitation for weather, hydrometeorological and climate applications; • standard analysis techniques that quantify the uncertainty of ground-based measurements over relevant time and space scales needed by satellite products; 3) to devise and implement regular procedures for the exchange of data on inter-comparisons of operational precipitation measurements from satellites;

3. Objectives of the IPWG: 4) to stimulate increased international scientific research and development in this field and to establish routine means of exchanging scientific results and verification results; 5) to make recommendations to national and international agencies regarding the utilization of current and future satellite instruments on both polar and geostationary platforms; and 6) to encourage regular education and training activities with the goal of improving global utilization of remote sensing data for precipitation measurements.

4. Three Working Groups – Operational Applications, Research and Validation Total of 21 Recommendations- Associated actions - a mix of short and long term. It was ambitious – but sets the stage for future IPWG activities They should be reviewed by Working Groups and refined with the benefit of two years experience First Meeting of IPWG – Madrid Spain, September 23-27, 2002

5. A web page designed for the precipitation community Reports, Algorithms, Datasets, Validation, Training, Meetings, etc http://www.isac.cnr.it/~ipwg/ Requirements for MW and sub-mm frequencies protection-Bizzaro Bizzarri Climate Monitoring principles - Phil Arkin Some Accomplishments

6. Links to validation AMSRE Validation network- Witek Krajewski Forecast verification-issues, methods- Beth Ebert QPF – validation NWP rain-tools – Beth Ebert Satellite validation rainfall –Beth Ebert SRDC – Mark Morrissey Links to Training CGMS Virtual Lab for Education and training CIRA Web based resource site for modelers, algorithm developers and users of passive MW data – Grant Petty Co-sponsorship with GPCP of assessment of global precipitation Algorithm Inventory and downloadable algorithms Accomplishments, cont’d

7. Inventory of routinely produced precipitation estimates either operational or experimental/research. Results on the IPWG web site: IR-based 5 Multiple blend 7 MW-based 5 MW-IR blended 5 EURAINSAT/A 1.0 – available for downloading- ( 12 requests )

8. Precipitation Validation IPWG/GPCP validation / intercomparison project. Validation of daily precipitation from a variety of algorithms: IR, MW, IR/MW, multi-spectral and NWP Beth Ebert - Australia http://www.bom.gov.au/bmrc/wefor/staff/eee/SatRainVal/sat_val_aus.html John Janowiak – USA http://www.cpc.ncep.noaa.gov/products/janowiak/us_web.shtml Chris Kidd – Europe http://kermit.bham.ac.uk/~kidd/ipwg_eu/ipwg_eu.html

10. Working Group Recommendations

11. Operational Applications Recommendation 1: Form a subgroup for the development of instantaneous precipitation estimation export algorithmsfor users of geostationary and low Earth-orbiting satellite data. Recommendation 2: Establish the IPWG web site http://www.isac.cnr.it/~ipwg/

12. Operational Applications Recommendation 3: Coordinate efforts and activities contemplating the use of satellite precipitation data for "non-traditional" e.g. snow models, irrigation models, pest and disease models, mud slide and avalanche models, dispersion models, surface pollution models and other applications. Recommendation 4: Make case study satellite datasets available through the IPWG website, for further algorithm research. Recommendation 5: Encourage continued development, refinement, and validation of the various research-status satellite sensor precipitation estimation techniques Recommendation 6: Coordinate satellite-based precipitation estimation research with the needs and requirements for climatological applications.

13. Research Activities Recommendation 1: Provide a generally accessible platform on data and algorithms for the research community. Recommendation 2: Enable co-operation and training through software libraries. Recommendation 3: Develop new strategies on flexible and global structures for physical algorithm development, validation, and data fusion. Establishing a framework for Physical algorithm development (global and regional). Developing a testbed for algorithm validation (comparison data sets etc.). Product merging and blending

14. Research Activities • Recommendation 4: • Develop different types of analysis/retrieval approaches to solve the principal problem of under-constrained precipitation retrievals. • The usefulness and complexity of the needed methodology and information depends on the application. Only by stronger constraints on algorithms can special retrieval problems be solved such as: orographic precipitation, light precipitation, frozen precipitation, resolution enhancement [spatial (vertical/horizontal) and temporal]. • Recommendation 5: • In view of future sensor development a long-term strategy for frequency protection has to be developed and integrated in the current ITWG activities.

15. Validation Activities Recommendation 1: Provide baseline validation standards for satellite precipitation algorithm(s) in terms of the needs of users in NWP data assimilation, nowcasting, hydrology, climate, and algorithm development communities. Recommendation 2: Ensure that members of the NWP data assimilation, nowcasting, hydrology, climate communities are represented at future IPWG meetings. Recommendation 3: Monitor performance of operational precipitation algorithms on a large scale on a daily basis, preferably in connection with NWP forecast validation. Recommendation 4: Support alternative approaches to error estimation such as physical error modeling and cloud/system classification to obtain global error estimates.

16. Validation Activities Recommendation 5: Create an inventory of existing high quality reference data. Recommendation 6: Encourage sharing of data from Intensive Observation Periods in large-scale experiments with the IPWG community, to enable improved validation of satellite rainfall estimates. Recommendation 7: Perform and develop new methods for the error characterization of reference datasets.

17. Validation Activities Recommendation 8: Encourage the use of dual-gauge systems and optimal network design in operational rain gauge networks, to improve the reliability and quality of rainfall observations. Recommendation 9: Investigate the quality and availability of surface reference networks for the validation of hard-to-measure (orographic, light, solid) precipitation. Recommendation 10: Develop an assessment software package, incorporating both basic and advanced techniques, to facilitate validation of satellite rainfall estimates by algorithm developers and users.