Validation is the process of assessing, by independent means, the quality of the data products derived from satellite instrument measurements.
Geophysical products are generated from satellite data by applying an algorithm that is either physically or empirically based. Comparing the retrieved products, and their trends with in-situ observations or model outputs is an important part of the process to assess and document the reliability of given retrieval algorithms in deriving these products as well as to define its domain of applicability.
For many products validation is a complex problem since the comparison between products derived from satellite measurements and independent reference products often from in situ measurements is subject to several errors: (1) an inherent satellite-derived product error, (2) the error in the reference data, and (3) the error introduced by the comparison methodology, often due to non-collocation in time and space.
Validation of satellite-derived parameters and products can be carried out using the following sources:
- Surface-based in-situ measurements
- Surface-based remote sensing measurements
- Model comparison and assimilation
- Other satellite-derived or blended products of a similar type