Validation strategy for satellite observations of tropospheric reactive gases

Satellite observations of tropospheric reactive gases are an integral part of the earth observing system but require continuous validation by independent measurements. For short-lived tropospheric species, the large variability in space and time results in specific challenges for validation, often combined with the scarcity of appropriate validation data. In this paper, the need for validation is discussed, previous work on validation of satellite observations is briefly reviewed, and the challenges and possible approaches for current and future validation networks are evaluated.