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Comparison of sensors, instruments and equipment, which are operationally applied for measuring meteorological variables, are important means of determining their performance characteristics under in-situ (field) conditions. If required, additional tests are carried out in the laboratory.
For the organizational preparation of these tests, carried out under the auspices of WMO/CIMO either regionally or globally, and especially for determining the test- and data evaluation- conditions as well as for developing the rules for participation at the intercomparison, the president of CIMO nominates recognized experts serving in an International Organizing Committee (IOC) which is established for each trial (see WMO-No. 8, informally called CIMO Guide ).
The results of intercomparisons are published in WMO’s Instrument and Observing Methods Report series (IOM Publications list). These reports also contain guidelines for WMO Member countries on improving the data observed, and conclusions particularly useful for instrument developers and providers to improve, among others, the performance and /or the reliability of the equipment concerned.
The fourth (reduced) session of the Joint Expert Team on Surface-Based Instrument Intercomparisons and Calibration Methods (ET) and International Organizing Committee on Surface-Based Instrument Intercomparisons (IOC) realized at Ghardaia. The ET/IOC inspected the intercomparison site of the WMO Field Intercomparison of the thermometer screens/shields in conjunction with the humidity measuring instruments in Ghardaďa, made suggestions to improve further its functionality and possible expansion of the site and selected additional instruments for the intercomparison. It checked the procedures and preliminary results of the laboratory calibration phase, procedures for the field installation, including the supervision and maintenance of instruments during the intercomparison period. The ET/IOC also agreed on the data acquisition and archiving, data processing, data policy and analysis methodology. It also updated the schedule of the intercomparison and agreed on the updated list of the participating instruments and instruction for their transportation to Ghardaďa.
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Presentation of some instruments selected for the field intercomparison:
| Socrima (French) |
large Stevenson screen, currently used by Algeria and many other countries, in many synoptic stations. While not initially proposed, the IOC considered that this screen should be included in the intercomparison.. |
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"Global solar radiation (irradiance): 800 Wm-2. (CM11B)
Surface albedo (CM14B); (value to be proposed by the PL)
Long-wave net radiation (CG4); (value to be proposed by the PL)
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| Davis Instruments (USA) |
INaturally ventilated screen PN7714, due to a large number of screens used operationally. Even if not normally used by NMHSs, many such screens have been used at voluntary climatological stations
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| Lanser (AUSTRIA) |
AArtificially ventilated Stevenson screen, due to an original design and number of screens in operation. |
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| Fischer & Co. (GERMANY) |
Artificially ventilated screen 431411, due to the original design, number of screens in operation. |
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-Hungarian Met. Service/ TS/HMS (HUNGARY) naturally ventilated screen. |
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| selected instruments: |
- Gerhard Herzog/G90 (GERMANY) naturally ventilated screen |
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- KNMI (The Netherlands) multiple naturally ventilated screen. |
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Global Observing System (GOS):
The coordinated system of methods and facilities for making meteorological and other environmental observations on a global scale in support of all WMO Programmes; the system is comprised of operationally reliable surface-based and space-based subsystems. The GOS comprises observing facilities on land, at sea, in the air and in outer space. These facilities are owned and operated by the Member countries of WMO each of which undertakes to meet certain responsibilities in the agreed global scheme so that all countries can benefit from the consolidated efforts.
pdf document
 World Meteorological Organization QUESTIONNAIRE I
World Meteorological Organization QUESTIONNAIRE II
Screen Histogramms Analysis
approach of GHARDAIA Climatology
Intercomparison JMM 2007
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