Quality management, calibration, testing and comparison of instruments and observing systems M. Leroy, CIMO ET on SBII&CM.
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Transcript Quality management, calibration, testing and comparison of instruments and observing systems M. Leroy, CIMO ET on SBII&CM.
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 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 1B 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, MétéoFrance has set up the following objectives;
some are less ambitious than the achievable
measurement uncertainty stated by the CIMO
guide.
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0.5 hPa 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
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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)
Some examples
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, 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)
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.