As stated by GCOS “Long-term, high-quality and uninterrupted observations of the atmosphere, land and ocean are vital for all countries, as their economies and societies become increasingly affected by climate variability and change”. High-quality observations are possible only if they are based on a sustained traceability to SI and with uncertainties associated to the measured ECVs.
Air
Air humidity is a key parameter in climate processes. A big challenge, for humidity sensors, is the wide dynamic range with a factor of more than 10000 of water content in the atmosphere. Reliable measurements require sensitive and fast responding sensors to quantify dynamic changes characterizing the phenomenon. Radiosondes sensors calibration protocols need to be improved and validated, to cover real conditions.
Sea
Two of the key oceanic ECVs, for monitoring and understanding decadal changes in heat content and transport, are temperature and salinity. A comprehensive study of the effect of the main quantities of influence (water pressure and temperature) on thermometers and salinometers is needed, for reducing measurement uncertainty, and validating their characterization.
Land
For land ECVs consistent measurement uncertainties calculations need complete knowledge of the measurement system: its intrinsic behaviour, other parameters of influence, siting etc.
WMO/CIMO2 notices the “importance of instrument intercomparison as a tool to improve the data traceability and the uncertainty calculation and to improve operational and maintenance procedures”. Although at present meteorological calibration laboratory intercomparisons are not satisfactory to guarantee full traceability and data comparability, and a well-defined protocol is missing.
Though the permafrost temperature is classified as a parameter to investigate climate changes, at present few or none are the measurement procedures reporting fully detailed uncertainty budget.
Calibration and measurements standards for precipitation and soil moisture are not yet well enough developed to solve differences between laboratory setup and natural conditions.
