Institute of Meteorology and Climate Research

Recommendations of the SPARC Activity "Towards Unified Error Reporting (TUNER)" published

During the last few years, the SPARC Activity "Towards Unified Error Reporting (TUNER)" developed recommendations on the characterization of satellite-borne temperature and composition measurements with regard to their uncertainty and vertical resolution. These recommendations have now been published in Atmos. Meas. Tech.

For the description of the data characterization a clearly defined language shall be used. The uncertainty characterization shall be as complete as possible. Substantive contributions from each relevant error component should be reported separately. Information should be provided if the error components are independent between two subsets of data within a certain domain (time, space, species, etc.). It should be indicated which of the error components contribute primarily to the random error and which contribute primarily to the systematic error. The meaning of the reported uncertainties shall be clarified (1-sigma, 2-sigma ...). Assumptions of the ingoing uncertainties of the error propagation calculations shall be made available. If the retrieval has used a priori information, this should be made available. In addition to the error budget, averaging kernels should be reported. The space to which the averaging kernel applies (e.g., linear/logarithmic, mixing ratio/density, absolute/relative, etc.) shall be reported. The smoothing error should not be included in the total error. The discretization and related interpolation schemes must be specified. If an altitude-resolved retrieval is performed in any other space than state value over altitude, pressure, or likewise (e.g., if eigenvectors or similar are used), then the final result should in addition be presented as vertical profiles and also all diagnostic data (error estimates, averaging kernels) should be transformed to the respective representation. In order to avoid unnecessary data traffic, retrieval scientists should judge whether evaluation of error budgets and averaging kernels for a limited number of representative cases is adequate. If averaging kernels are only provided for a few representative cases, one might still consider to show at least the vertical resolution profiles for each profile. If representative error estimates are reported instead of error estimates for each single profile or data point, it is of utmost importance to tell the data user if the nature of each error component is chiefly additive or is chiefly relative. If certain estimated errors or other characterization data are known or suspected to depend systematically on time, latitude, or other parameters, this dependence should be reported. If, for application to mean profiles, mean averaging kernels are provided in conjunction with mean profiles instead of individual ones, then the
correlation profiles between the averaging kernels and the retrieved profiles shall be provided. If only standard deviations are reported for the individual profiles instead of the full covariance matrices, then a representative random error correlation pattern in the altitude domain shall be made available. The error estimates should explain observed differences between measurements of the same airmass.

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