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Surface-Based Instrument Intercomparisons and Calibration Methods

This activity report discusses the organization and preparation of surface-based instrument intercomparisons, including laboratory intercomparison of rainfall intensity measuring instruments, combined intercomparison of thermometer screens/shields with humidity measurements, and draft recommendations for calibration methods.

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Surface-Based Instrument Intercomparisons and Calibration Methods

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  1. Commission for Instruments and Methods of ObservationFourteenth SessionGeneva, 7 – 14 December 2006 Surface-Based Instrument Intercomparisons and Calibration MethodsActivity Report Draft recommendations Michel Leroy Chair of the ET-SBII&CM

  2. Organization and Preparation of surface-based intercomparisons • Terms of reference : • Laboratory intercomparison of rainfall intensity (RI) measuring instruments. • Combined intercomparison of thermometer screens/shields, in conjunction with humidity measurements, in various climatic regions

  3. Laboratory intercomparison of RI instruments • Following recommendations of an expert meeting in Bratislava (2001) and CIMO XIII, first step before a field intercomparison. • International Organizing Committee established. • Three laboratories : • DIAM, University of Genoa, Italy; De Bilt, KNMI, the Netherlands; Trappes, Météo-France. • 4 meetings for the laboratory intercomparison: • Trappes (2003), Genoa (2005), De Bilt (2005), Geneva (2005)

  4. Laboratory Intercomparison • Project Manager : Prof. Luca Lanza. • 15-Sept-2004  15-Sept-2005 • Catching type instruments. • 19 (pairs) of instruments, divided in 3 groups. • Shift of instruments between laboratories. • Final Report available from the CIMO/IMOP Website since January 2006.

  5. Outcomes of laboratory intercomparison • Each laboratory used its own testing device, based on constant flow and weighing. • Proposal of a standardized procedure for laboratory calibration of catchment type rainfall intensity gauges. Draft Rec. 4.2/1 • To be included in CIMO guide. • Some tipping-bucket rain gauges with proper correction software and some weighing gauges satisfy the WMO RI requirement over limited RI ranges (±5% 2 – 2000 mm/h)

  6. WMO Field Intercomparison of Rainfall Intensity Instruments • The laboratory Intercomparison was a first step, easier to handle than a field test. • Not all instrument types available on the market were tested in laboratory. • Looking for a possible site, Vigna di Valle, Italy (Italian Meteorological Service, ReSMA) was selected. August 2007  August 2008

  7. Field Intercomparison • Call for instruments (March 2006) • 24 instruments of different measuring principles were selected (54 proposed !). • Reference based on a set of high quality devices, inserted in a pit gauge. • Draft Rec. 4.2/2 : Procedure and reference instruments for field rainfall intensity intercomparisons

  8. WMO Combined Intercomparison of Thermometer Screens/Shields, in conjunction with Humidity Measuring Instruments • Looking for a possible site in harsh conditions, Ghardaïa, Algeria was selected. • Desert region • Jan. 2007  Jan. 2008 • Instruments’ calibration before and after

  9. Screens & Hygrometers Intercomparison • Call for instruments (March 2006) • 16 screens/shields’ types (29 proposed) and 11 hygrometers’ types(17 proposed) were selected. • Reference : Thygan • Data analysis : • International Organizing Committee • ISO standard 17714 (draft)

  10. Intercomparisons • Heavy load for the organizing country • Heavy load for the ET and IOC members • That explains the possible time delays in organizing an Intercomparison. • Successful participation of HMEI, in proposing instruments to be tested (directly or in conjunction with a WMO member). • Any help for intercomparisons ?

  11. Future Intercomparisons • Field RI Vigna di Valle, Italy : 2007-2008 • Screens/humidity Ghardaïa, Algeria : 2007-2008 • Intercomparisons in harsh climate conditions : artic, desert, tropical, marine, urban ? • Intercomparison of Present Weather Sensors ?

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