Surface-Based Instrument Intercomparisons and Calibration Methods

Activity Report Draft recommendations

Michel Leroy Chair of the ET-SBII&CM

Commission for Instruments and Methods of Observation

Fourteenth SessionGeneva, 7 – 14 December 2006

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

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)

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.

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)

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

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

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

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)

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 ?

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 ?