MADIS Quality Control
The QC procedures are, for the most part, provided by the NWS Techniques Specification Package (TSP) 88-21-R2 (1994).
Two categories of QC checks, static and dynamic, are described in the TSP for a variety of observation types, including most of the observations available in the different MADIS datasets. The static QC checks are single-station, single-time checks which, as such, are unaware of the previous and current meteorological or hydrologic situation described by other observations and grids. Checks falling into this category include validity, internal consistency, and vertical consistency. Although useful for locating extreme outliers in the observational database, the static checks can have difficulty with statistically reasonable, but invalid data. To address these difficulties, the TSP also describes dynamic checks which refine the QC information by taking advantage of other available hydrometeorological information. Examples of dynamic QC checks include position consistency, temporal consistency, and spatial consistency.
The TSP also describes single-character "data descriptors" for each observation, which are intended to provide an overall opinion of the quality of the observation by combining the information from the various QC checks. Algorithms used to compute the data descriptor are a function of the types of QC checks applied to the observation, and the sophistication of those checks. Level 1 QC checks are considered the least sophisticated, level 3 the most sophisticated checks.