Smoothing and co-location uncertainty libraries

GAIA-CLIM is supporting the European Commission’s Copernicus Programme by assessing and improving the fitness-for-purpose of sub-orbital (ground- and balloon-based) reference measurements for the validation of observational data sets from satellites. Amongst others, the project aims at improved traceability and uncertainty characterization of the individual sub-orbital measurement systems, and of the comparison with satellite data.  The latter implies the need for a rigorous treatment of so-called co-location mismatch uncertainties. These are the result of (differences in) smoothing and sampling properties of the various ground-based and satellite observing systems. These differences matter because the atmosphere is inhomogeneous and variable on the scale of individual measurements and on the scale of a typical co-location. Consequently, sampling and smoothing differences yield real physical and chemical differences, which have nothing to do with the measurement performance per se. Two perfect measurements measuring a slightly different volume and time integral are a priori expected to differ.   

Within GAIA-CLIM, several methods have been developed for - and applied to - the quantification of smoothing and sampling issues in a range of atmospheric ground-based measurement techniques, and to estimate the uncertainties that need to be taken into account when comparing non-perfectly co-located ground-based and satellite measurements with different spatio-temporal smoothing and sampling properties. The motivation for these developments and the principles of the different methods has been described in deliverable D3.2 (“Generic metrology aspects of an atmospheric composition measurement and of data comparisons”), and a wide variety of applications were performed and reported on in D3.4 (“Measurement mismatch studies and their impact on data comparisons”).

To translate these developments and results into a practical, usable resource for Copernicuas Climate Change Services users, two avenues were foreseen within GAIA-CLIM: (1) an integration of (derived) tools into the Virtual Observatory (VO), where they serve to estimate smoothing, sampling, and co-location uncertainties for the data ingested into the VO and for the satellite-ground co-locations performed by that system, and (2) publication of libraries (i.e. guiding material and data files) of such uncertainties for key ground-based measurement systems and for key comparisons. The former avenue constitutes the material for deliverables D3.5 ("Tools for quantification and smoothing uncertainties for integration in development of VO") and D3.7 ("Final version of tools for quantification of collocation mismatch and smoothing uncertainties and associated documentation for integration in the virtual observatory"), while the latter is the topic of the deliverable D3.6 ("Library of (1) smoothing/sampling error estimates for key atmospheric composition measurement systems, and (2) smoothing/sampling error estimates for key data comparisons").

The actual data files, are available for download (by anonymous/guest ftp) at: