As with many operational systems, preprocessors play an absolutely essential role.  Preprocessors are used to reformat, perform conversions, and carry out other functions on data before further processing or application of the data is made.  In the NWSRFS this includes, but is not limited to, such tasks as aggregating or disaggregating temporal distributions, filling in missing data, and checking for units and consistency.

For example, a particular precipitation gage may report rainfall on a 24-hour time interval; however, it is necessary to have this data in 6-hour intervals.  In this case the preprocessor would disaggregate the data from a single 24-hour value into a series of 6-hour values, often based on data from nearby stations that report at a smaller time interval.

Figure 1

Preprocessors are used to finalize or organize data of all types including rainfall, snowfall, temperature, river and stream flow, and reservoir data.  The data may also be forecasted or predicted data as in the case of a using forecasted precipitation amounts to compute a mean areal precipitation or MAP.

It is understood that there are often differences between the calibration and operational systems. This module addresses the operational system. For additional discussion on these differences, click below: