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Quality management, calibration, testing and comparison of instruments and observing systems M. Leroy, CIMO ET on SBII&CM
Quality management, some aspects § § Explicit identification of uncertainty objectives Representativeness of observations Calibration and maintenance Selecting instruments : knowing their characteristics – Testing – Intercomparisons § Composite observing systems § Value analysis § ISO 9001 -2000 is an international frame
Quality management process § § Setting and documenting objectives Defining associated indicators Regular survey of users’ (customers) needs and satisfaction. § Correcting and improving
Identification of uncertainty objectives § Identification of users of observation data – Forecasters and climatologists – Few direct users of observation : special case is aeronautic users, with needs clearly defined in Annex 3 of ICAO. § Getting the users’ needs is not always easy – They are not always aware of the possible uncertainty and associated cost. – A value analysis is necessary to get a good compromise. § The CIMO guide (WMO doc n° 8) is a guide. – Annex 1 B indicates users’ needs and achievable measurements (best state of the art). § The measurement uncertainty must be demonstrated. So realistic choices must be done.
An example § For his proprietary Radome network, mainly dedicated for real-time observation, Météo. France has set up the following objectives; some are less ambitious than the achievable measurement uncertainty stated by the CIMO guide. – – – 0. 5 h. Pa for pressure 6% for relative humidity 0. 5°C for air temperature 10% for wind speed 5 -10% for precipitation amount 5% for daily amount of solar radiation.
§ For other objectives, additional care can be necessary § Example : US Climate Reference Network – – Redundancy and cross check of measurements. 3 independent air temperature measurements. Dual fence rain gauge. Associated measurement of wind speed. § Such efforts cannot be made in each station of a climatological cooperative network.
Quality indicators § Availability of data in the (final) data base – Within a given limit of time : example 95% of expected surface observations available within 10 minutes. – Availability of data in the climatological data base : example 98% for the Radome network. § Measurement uncertainty – % of sensors calibrated in a stated delay : example 12 months nominal, 15 months maximum, objective is more than 90%. – % of sensors found outside an Acceptable User Limit : example hygrometers found with one (or more) control point more than 5% from the reference. These sensors are flagged as having drifted. – % of sensors for which the periodicity of preventive maintenance is respected. – % of large errors when compared to numerical models (monitoring)
Knowing the characteristics of an instrument § Technological survey : reading publications, participating to conference and instrument exhibitions. § Testing of instruments : please, publish results and make them available. § Intercomparisons, WMO intercomparisons. § Read the manufacturers’ technical documentation, having in mind the common characteristics of instruments, for example, thru the CIMO guide.
Recent WMO intercomparisons § Radiosonde intercomparisons § WMO Laboratory Intercomparison of Rainfall Intensity gauges § WMO Field Intercomparison of RI gauges : May 2007 -May 2008, Vigna di Valle, Italy § WMO Intercomparison of Thermometer Screens/Shields in conjunction with Humidity Measurements : 2007, Ghardaïa, Algeria
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, Re. SMA) 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)
Conclusion § There are many other subjects and actions concerning quality measurement : – Quality control directly at the level of the measurement systems. – Quality control using spatial and temporal cross-check. – Representativeness of observations, due to the nearby environment of the measuring site. – … § Quality management and ISO 9001 -2000 certification force us to explicit the objectives of observing networks and the proofs demonstrating their achievement.