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.